Tuesday 26 August 2014

Cognizant HR Interview questions and answers





Cognizant HR Interview questions and answers

About Cognizant:

Cognizant


The Cognizant technology Servicesprivate limited is a multinational IT company. It provides solutions regarding software, Business process outsourcing and technological services. The company is headquartered in New Jersey, United States. The company started in 1996 and was initially headquartered inChennai, India. Then it later on moved its headquarter to New Jersey, United States. The IPO of the company became public in 1998. It was in fact the first Indian software firm to be enlisted on NASDAQ. The company got listed as a fortune 500 company in the year 2011. Thus, as you could understand the standard of the company, thus the recruitment process of the company is also that tuff. Here, for your help are some Cognizant HR interview questions.


Cognizant HR Interview questions:
1. Tell us something about yourself.

This is the first question, you can expect during any interview you face. This usually is a question to start the communication and set the ball rolling for the interview. You can answer this question by providing some information about your work experience, technologies you have worked upon, educational qualifications. If you are a fresh graduate, you can provide some information about your family also.

The trick is to put the full stop at the right place to provoke the next question you want. For e.g. “Recently I developed a website using Drupal. It was quite an interesting but challenging job which I enjoyed.”
2. Why do you consider yourself a suitable candidate for this position?

The answer to this question lies in the preparation you did before the interview. It is extremely important that you research the requirements of the position well and match them with your skills.

For e.g. if the position requires an Asp.net developer with good knowledge of health care domain, tell the interviewer about your technical skills and your domain knowledge.

Fresh graduates can talk about their technical skills, ability to learn and grasp things quickly.
3. Why do you want to leave your present job or company?

You may want to leave your present job for any reason but make sure that you do not talk bad about your manager, company or job. It reflects your complaining attitude.

Provide a sincere reason for e.g. “I think, I have grown up with my last employer as much as I could. I want to grow further and I believe that is possible with a new employer.”
4. You have stayed in your current job for quite a long time, why?

There are many people who do not change their jobs for years and when they go out looking for a new employer, this is one of the most important questions they are asked. Some people might look upon staying with the same employer for long as “lack of ambition”.

A good answer to this question can be something like, “Yes, you are right. I stayed with my last employer for almost 5 years but I was continuously growing in the company, doing new things, handling bigger challenges. So, I was quite happy working with them for these many years.” You can then talk about how you grew with your last employer.
5. What do you know about us?

Research the company and its business a bit before appearing for the interview. Also, find out a bit about the technologies they work upon. You don’t need to know everything inside out but having a fair idea about the company makes you appear interested in the position, to be taken seriously.

For e.g. I see that your company does a lot of projects based on OpenSource platforms like Joomla, Drupal, Magento which is quite interesting as I have a similar kind of experience.
6. What do you do to improve your knowledge?

The field of IT is very revolutionary. It is extremely important to keep yourself abreast with the new technological developments and this needs you to take some time out of your work schedule so that you can keep sharpening your saw.

To answer this question, you can tell the recruiter about the forums which you keep visiting, blogs which you keep reading. It will be an advantage if you are a member of some local user group.
7. Can you perform under pressure?

Most of the times, the job of software development is that of working under pressure. Sometimes, it will be the pressure of delivering on time while it can be that of a bug that has sprung all of a sudden in your code.

So, expect pressure in everything you do. It is important to maintain your performance and develop strategies to deliver under pressure. You can then go ahead an talk about your way of dealing with pressure and performing under it.
8. Tell us some of your strengths.

Again, it is important to study the requirements of the position before you appear for the interview. List out your strengths and offer the ones that this role demands.

For e.g. if you are appearing for the position of a Tech Lead – VB.net, talk about your VB.net skills, any extra knowledge which you have about coding with VB.net in comparison to other candidates, your team management skills etc.
9. Tell us some of your weaknesses.

You have to be careful while answering this question. Do not offer a weakness which will directly affect your selection but at the same time saying that you do not have any weakness will not be right too. Every human being has weaknesses, so it is perfectly OK for you to have some too.

The best way to answer this question will be to turn one of your strengths as a weakness and say that others accuse you of having this weakness but you think it is important to work in this manner. For e.g.: “My colleagues accuse me of paying to much attention to syntaxes but I believe it is important when you are writing the code to avoid spending too much time on finding and fixing the bugs later on.”

Another way to answer this question is to offer a totally un-related weakness for e.g. “I have been staying alone for so many years now but I still can’t cook independently.”
10. Are you comfortable working in a team?

The whole work of software development or IT is a team work. So, the only answer to this question can be: “Yes, I am comfortable working in a team.” If you have any problems in working as a team, it is important to work on them and develop yourself as a team player.

Here are some of the best Cognizant HR interview questions. To excel in Interviews you can follow these Cognizant HR interview questions.

For more HR interview questions please download pdf: 

Wipro Technical interview questions and answers





Wipro Technical interview questions and answers
About Wipro:

Wipro office


The Wipro limited is a major IT consultingand system integration services company that is headquartered in Bangalore, Karnataka, India. According to the count on march 2014 the company has a total of 146,000 employees and the company is serving about 900 large organizations and has a presence in more than 61 countries. The market capitalization of the company was Rs. 1.27 trillion ($ 20.8 billion). This makes it one of the biggest IT sector companies in India. Azim Premji is a huge share holder in Wipro. He hold more than 50% of the companies share.

Now, one can understand the standard and the strength of the company. Thus, entering into such a company will be tuff. The interview process is thus standard. These here are the best Wipro technical interview questions.


Let us take a look at the Wipro technical interview questions:
Explain Memory management in C.

The C programming language manages memory statically, automatically, or dynamically.

Static-duration variables are allocated in main memory, usually along with the executable code of the program, and persist for the lifetime of the program

Automatic-duration variables are allocated on the stack and come and go as functions are called and return.

For static-duration and automatic-duration variables, the size of the allocation is required to be compile-time constant.

Dynamic memory allocation in which memory is more explicitly (but more flexibly) managed, typically, by allocating it from the heap, an area of memory structured for this purpose.

In C, the library function malloc is used to allocate a block of memory on the heap. The program accesses this block of memory via a pointer that malloc returns. When the memory is no longer needed, the pointer is passed to free which deallocates the memory so that it can be used for other purposes.


Functionality of Operating System?

An operating system (OS) is a set of software that manages computer hardware resources and provides common services for computer programs.
To act as interface between hardware and users, an operating system must be able perform the following functions:

1. Enabling startup application programs. Thus, the operating system must have:

- A text editor

- A translator

- An editor of links
2. The allocation of resources needed to execute programs is done by identifying: the programs that are running, the need for memory, peripheral devices and data protection requirements.



3. Facilities for data compression, sorting, mixing, cataloging and maintenance of libraries, through utility programs available.

4. Plan implementation works according to certain criteria, for efficient use of central processing unit.

5. Assisting implementation of programs through computer-user communication system, at both hardware and software level.

Examples of operating systems:BS2000,BS3000,DOS,PC-DOS,MS-DOS,LINUX,SOLARIS,MAC OS,UNIX,WINDOWS.


What is the use of IP address?

An Internet Protocol address (IP address) is a numerical label assigned to each device (e.g., computer, printer) participating in a computer network that uses the Internet Protocol for communication.An IP address serves two principal functions: host or network interface identification and location addressing
What is difference between UNIQUE and PRIMARY KEY constraints?

A UNIQUE constraint is similar to PRIMARY key, but you can have more than one UNIQUE constraint per table. Contrary to PRIMARY key UNIQUE constraints can accept NULL but just once. If the constraint is defined in a combination of fields, then every field can accept NULL and can have some values on them, as long as the combination values is unique.
What are the steps involved in designing?

Project plan, Requirements, Design, Coding, Testing, Re-coding and design, Development, Maintenance.
what is the difference between interface and multiple interface?

Both an abstract class and an interface are specific types of computer objects that allow a programmer to loosely define one type of object as if it were another type, while retaining all of the object’s original properties. While multiple different computer languages use one or both of these concepts, Java is the most well-known. Abstract classes and interfaces have a variety of similarities, but also incorporate significant differences in structure, syntax, and usage.
How can we delete Duplicate row in table?

SQL> delete from table_name where rowid not in (select max(rowid) from table group by duplicate_values_field_name);
When do you use SQL Profiler? 

SQL Profiler utility allows us to basically track connections to the SQL Server and also determine activities such as which SQL Scripts are running, failed jobs etc..
What do you mean by active and passive objects?

Active objects are one which instigate an interaction which owns a thread and they are responsible for handling control to other objects. In simple words it can be referred as client.
Passive objects are one, which passively waits for the message to be processed. It waits for another object that requires its services. In simple words it can be referred as server.

10. What do you mean by static and dynamic modeling?

Static modeling is used to specify structure of the objects that exist in the problem domain. These are expressed using class, object and USECASE diagrams.
But Dynamic modeling refers representing the object interactions during runtime. It is represented by sequence, activity, collaboration and state chart diagrams.

The above article provides the most common Wipro technical interview questions. One should read these Wipro technical interview questions properly to have a good interview.

Infosys HR interview questions and answers





Infosys HR interview questions and answers

About Infosys:

infosys Limited

Infosys is an Indian multinational company that provides solution in IT field and Business consulting, software engineering and many outsourcing company. The company is headquartered in Bengaluru (Bangalore) and was founded in the year 1981 by N. R. Narayana Murthy, Nandan Nilekani, N. S. Raghavan, S. Gopalakrishnan, S. D. Shibulal, K. Dinesh and Ashok Arora as a joint venture. The company has been a leader in outsourcing and services since then. The company became a big name with the passing time and now it is one of the leading companies in India. If measured in terms of revenue, the company is the 3rd largest IT company in India. The company has a tough and stiff recruitment process. Thus, for the help aspirants here are some good Infosys HR interview questions. 
Infosys HR interview questions and answers:

Question 1. Tell me about yourself ?

Answer: It is the most often asked question in interviews and also the most tricky question. Start by telling why you are well qualified for the position. Remember, always match your educational & experience qualification to what the interviewer is looking for. In other words you should give information what the interviewer is looking for. Be careful that it should not seem rehearsed.

Question 2. What are your greatest strengths?

Answer: Number of answers are good to give, but in positive manner. Some good instances are:

About your problem solving skills, ability to work hard, professional expertise, leadership skills, positive attitude etc.

Question 3. Do you have any blind spots?

Answer: Disguise your strength as a weakness. Beware this is an eliminator question, designed to shorten the candidate list.

Question 4. Why should I hire you?

Answer: Try to know the interviewer’s greatest needs and demands, this question will give you advantage over other candidates and give him best facts for hiring you than someone else.

Question 5. Why did you leave your last job?

Answer: Always answer in a positive manner regarding reason. Never talk negatively or badly about your previous organization. If you do, you will cut a sorry figure. Give suitable reasons for leaving last job.

Question 6. Where do you see yourself five years from now?

Answer: Don’t be too specific. Make assure interviewer that you wanna make a long-term commitment with the organisation and this is the exact position you are looking for.

Question 7. Describe your management style?

Answer: Tell about some common labels as progressive or consensus etc. can have several meanings or descriptions depending on which management expert you listen to. The situational style is safe, and fits to all.

Question 8. Are you a team player?

Answer: Of course, I’m a team player. Always say this and should have examples ready. Tell that you often perform for the good of the team rather than mean is good evidence of your team attitude.

Question 9. How would you be an asset to our organization?

Answer: Highlight and let them know about your strengths. This is the exact question where you can win their heart and with confidence.

Question 10. Do you have any questions for me?

Answer: Always have some questions prepared for the interviewer. How soon will I be able to be join? etc.

Here are the Infosys HR interview questions. Read these questions for a better HR interview. All the best for your interviews!!

For more questions and answers both technical and HR please download pdf: 



Infosys technical interview questions and answers





Infosys technical interview questions and answers

About Infosys:

placement criteria for infosys

Infosys is global leader in IT services and software. It is an Indian software company. It is an Indian multinational company that is enlisted on the NASDAQ and Bombay Stock Exchange. The company is headquartered inBangalore, Karnataka. Based on the revenue, it was the third largest IT company in India. The company was founded in 1981 By the combined effort of N. R. Narayana Murthy, Nandan Nilekani, N. S. Raghavan, S. Gopalakrishnan, S. D. Shibulal, K. Dinesh and Ashok Arora. Since then the company has crossed many hurdles and has reached this height of success. Here are the Infosys technical interview questions and answers.

Before going through the sample papers of Infosys technical interview questions we should see the common errors by aspirants in the interview:

1. One common mistake by candidates is to arrive late in the interview process.

2. Don’t Dress up too flashy. Try to dress up in a conservative suit and minimal amount of jewelry, wear low heals polished.

3. Playing zombie is one more problem. Actually people out of nervousness cannot talk and thus become stiff and cant make eye contact.

4. No Smoking, No Gum and No Drinking.

5. Not being able to articulate ones own strength and weaknesses.
Infosys technical interview questions:

1.What are the 4 basics of OOP? 

Abstraction, Inheritance, Encapsulation, and Polymorphism.

2.What you mean by Object Relational DBMS?

An object-relational database (ORD), or object-relational database management system (ORDBMS), is a database management system (DBMS) similar to a relational database, but with an object-oriented database model: objects, classes and inheritance are directly supported in database schemas and in the query language. In addition, just as with proper relational systems, it supports extension of the data model with custom data-types and methods.

3.what is database Schema?

The formal definition of database schema is a set of formulas (sentences) called integrity constraints imposed on a database.

4.what are the different levels of database schema?

Conceptual schema- a map of concepts and their relationships.
Logical schema- a map of entities and their attributes and relations
Physical schema- a particular implementation of a logical schema
Schema object- Oracle database object

5. what is difference between foreign key and reference key ? 

Reference Key is the primary key that is referenced in the other table (linked via the other tables Foreign Key). Foreign Key is how you link the second table to the primary tables Primary Key (or Reference Key).

6. Tell me about DSN?

A Data Source Name (DSN) is the logical name that is used by Open Database Connectivity (ODBC) to refer to the drive and other information that is required to access data. The name is used by Internet Information Services (IIS) for a connection to an ODBC data source, such as a Microsoft SQL Server database. To set this name, use the ODBC tool in Control Panel.
click->start in control panel->double click Administative Tool->click ODBC data source->click System DSN tab->click Add

7.Difference between Clustered index and non clustered index ? 

Clustered Index
Only one per table
Faster to read than non clustered as data is physically stored in index order
Non Clustered Index
Can be used many times per table
Quicker for insert and update operations than a clustered index

8. What is the difference between an EXE and a DLL? 

The term EXE is a shortened version of the word executable as it identifies the file as a program. On the other hand, DLL stands for Dynamic Link Library, which commonly contains functions and procedures that can be used by other programs.

9.Tell how to check whether a linked list is circular.

Create two pointers, each set to the start of the list. Update each as follows:
while (pointer1) {
pointer1 = pointer1->next;
pointer2 = pointer2->next; if (pointer2) pointer2=pointer2->next;
if (pointer1 == pointer2) {
print (“circular\n”);
}
}

Thus, these are the most commonly asked Infosys technical interview questions. Read these Infosys technical interview questions for better Interview process.

Environmental science and engineering 2014 Questions Bank


Environmental science and engineering 2014 Questions Bank


Environmental science and engineering
Question Bank (8 marks)

UNIT-I

1. a) Explain in detail the causes, effects and control measures of Deforestation
b) Discuss the problems of fertilizers and pesticides of modern agriculture

2. a) Discuss the effects of dams on forests and tribal people
b) Discuss the various types of land degradation with its causes and solutions.

3. Write short notes on causes effects and control measures of soil erosion
4. Write short notes on environmental impacts of mining
5. Write short notes on renewable energy resources

UNIT-II

1. Explain in detail the structure and component of an eco system.

2. Explain the characteristic features and functions of forest eco system and aquatic eco system

3. Explain the characteristic features and functions of Grassland eco system and Desert eco system

4. Write short notes on food chain and food web

5. Write short notes on ecological succession and ecological pyramids

6. Write short notes on i)Genetic diversity

ii) Species diversity

iii) Ecosystem diversity

7. Write short notes on threats to bio diversity

8. Write short notes on hotspots of biodiversity

9. Discuss India’s mega-diverse biodiversity

10. a)Explain the In-situ and Ex-situ conservation of biodiversity

b) Discuss the values of Bio-diversity

UNIT-III

1. Explain in detail the causes and effects of air and water pollution

2. Explain in detail the causes and effects of marine and noise pollution

3. Write short notes on (i) Bhopal gas tragedy and (ii) Chernobyl disaster

4. Write short notes on Disaster management

5. What is an earth quake? Enumerate its effects. What measures should be

taken to mitigate this disaster?

6. Explain in detail the causes, effects and control measures of NOISE and

THERMAL pollution.

7. Explain in detail the process of solid waste management







UNIT-IV

1. What is sustainable development? Discuss in brief the concept of sustainable

development.

2. What are waste lands? Name and discuss the various methods of waste land

reclamation.

3. Write notes on (i) Global warming

(ii)Ozone layer depletion

(iii)Acid rain

4. Write notes on Water shed management

5. What is rain water harvesting? Name and discuss in brief the types of rain Water

harvesting.

6. Write note on salient features of Environmental protection act and wild life

protection act

7. Discuss the salient features of Forest act

8. Write note on salient features of water act and air act

UNIT-V

1. Explain the term population explosion. Enumerate its effects.

2. What is value education? Discuss the concept of value education.

3. Discuss in detail the role of Information technology in environmental

management and human health.

4. Explain the activities of family welfare programme.

5. Discuss the problems, diagnosis and control of AIDS.

6. Write a note on women and child welfare.

Monday 25 August 2014

TCS HR Interview questions with Answers



TCS HR Interview questions with Answers




About TCS:

TCS


The TATA Consultancy Services is a huge IT company which is a subsidiary of the enormous TATA group. The TATA group was established back in 1869 by Jamsetji Nusserwanji Tata. But this subsidiary was established by Mr. Jehangir Ratanji Dadabhoy Tata (JRD Tata) in the year 1968. At present the Chairman is Cyrus Pallonji Mistry who over took it from Ratan TATA in 2012. The CEO and the Managing Director of TCSpresently is Mr. Natarajan Chandrasekaran. The company is presently having a revenue of $13.4 billion and has over 300,000 IT consultants working with the company. The company came in the 40th position on the Forbes magazine amongst the list of top innovative companies in the world. If measured by the revenue, it comes to be the worlds 10th largest IT services provider. Here are the TCS HR interview questions.
TCS HR interview questions:

1. Introduce Yourself ?
Start with the present and tell why you are well qualified for the position. Remember that the key to all successful interviewing is to match your qualifications to what the interviewer is
looking for. In other words you must sell what the buyer is buying. This is the single most important strategy in job hunting.

Suggestion: your answer to this question should cover your educational background very briefly. You should talk about your achievements, if any, either in your academic or in work or both.
Then you can add a few details about what type of person you are, your likes, dislikes, etc. Giving details about your family background is not compulsory. Before interview frame a good answer and practice in front of a mirror.

2. Why should I take you in TCS?
Whether your interviewer asks you this question explicitly or not, this is the most important question of your interview because he must answer this question favorably in is own mind
before you will be hired. So help him out! Walk through each of the position’s requirements as you understand them, and follow each with a reason why you meet that requirement so well.

3. Who inspired you to become an Engineer?
Make pre preparation for such questions. Have a few heroes /Leaders of the industry in mind , who have achieved something extraordinary in their life.
Know about their life history and mention one such name with his achievements. Cite some of his quotes or values possessed by such a personality that according to
him has been the cause of his extraordinary success. Mention such qualities /Values that will be highly valuable in your success in the position you are being interviewed.

4. What is your weakness?
Do NOT mention key weaknesses here. This is not the place to say you are bad at meeting deadlines or you never mastered highschool mathematics etc. Turn this question around to your benefit. For example, you are ‘over ambitious’ or ‘extremely attentive to detail’ or ‘like to take on too many projects’. Make it sound positive.

5. Extra co-curricular activities?
Explain work you have done apart from your studies.

6. Are you a team player?
You are, of course, a team player. Be sure to have examples ready. Specifics that show you often perform for the good of the team rather than for yourself are good evidence of your team attitude. Do not brag, just say it in a matter-of-fact tone. This is a key point.

7. Why should we hire you?
Again, explain that you are very interested in the job and demonstrate what it is about your past experiences, education and qualifications that makes you ideal for the job. Show enthusiasm and support your answers with evidence wherever you can. Elaborate on all the past experiences and skill sets that make you suitable for the job. In cases where your past experience is not directly relevant, you can still find elements of it that can be useful. Play up team skills, computer skills, leadership roles, specific courses and independent research activities that can be useful to the job at hand to show your initiative even where you don’t have directly relevant job experience.

8. Tell me about your dream job?
Be honest. Also mention keywords such as challenging, steep learning curve, good work culture, demanding, rewarding, opportunities for advancement and growth, team environment, opportunity to build and maintain client relationships etc.

9. What is more important to you: the money or the work?
This one will reveal the real you. Money is always important, but the work is the most important. There is no better answer.

10. Are you willing to work overtime? Nights? Weekends?
This is up to you. Be totally honest.

11. Would you be willing to relocate if required?
You should be clear on this with your family prior to the interview if you think there is a chance it may come up. Do not say yes just to get the job if the real answer is no. This can create a lot of problems later on in your career. Be honest at this point and save yourself future grief.

Tell me about the recent trends in IT industry?
Be prepared with two or three trends that illustrate how well you understand your industry. You might consider technological challenges or opportunities, economic conditions, or even regulatory demands as you collect your thoughts about the direction in which your business is heading.

If you are rejected today, then what will you do?

Well this question does not mean that they are rejecting you. So don’t get dishearten. This is more like a ‘stress question’ to judge how you react during a stress situation. This could also be because they want to know your other plans like if you have also applied for other companies or if you are very adamant about joining TCS. Either ways it does not mean that they are going to reject you. And make sure your answer is positive.

Where you’re native place is and for what it is famous?

You obviously know your native place right? But its better you also learn few things about the place as well. This is something about you, and you will be expected to know these little details.

12. Who is the founder of Google?
Mr. Larry Page and Mr. Sergey Brin? Well yes. But, did you really knew this? No?

Who are the competitors of TCS in the world market as well as in Indian market?

A little study about the current market should certainly help. A good homework will reflect in your answer and that will really be impressive. This will show the interviewer that you are concerned about this interview and job.
Infosys, Wipro, HCL Tech, Oracle Financ,Mahindra Satyam, Tech Mahindra, Mphasis, Patni Computer
How you rank yourself compared with your friends?



13. Who is the founder of TCS?
Jamsetji Nusserwanji Tata established TATA Group in 1869. However it was under Mr. Jehangir Ratanji Dadabhoy Tata (JRD Tata), that this group was expanded and hence TCS was established in 1968. Currenty Mr. Ratan Tata is the Chairman of the group.

Who is the present CEO?

Mr. Natarajan Chandrasekaran is the Chief Executive Officer (CEO) and Managing Director of the company. If you did not know this basic fact about TCS, then you have not done your homework well. Be ready for such questions.

14. What is the name of the award TCS recently received?

Tata Consultancy Services (TCS), has won six awards for outstanding HR leadership at Asia’s Best Employer Brand Awards 2010, in Singapore.

Award for Talent Management
Award for Excellence in HR through Technology
Award for Continuous Innovation in HR Strategy at Work
Award for Innovation in Recruitment
Award for Innovative Retention Strategy
Award for Excellence in Training

15. What is your aim?
Be honest at this part, because all that the interviewer wants to know is whether your aim and goal match with the company’s objective or not.

16. Wat r u r skills? Do u have any certifications on u r skills?

Yes? Well good, however be ready with your certificates to show them (if asked). And if your answer is a No, then be ready to answer ‘why no’!

17. There’s a bond of 2 years ……. you’ re ok with it?

Be totally honest and do your home work about these things. and be prepared for the question.

18. You’ll be sent to any part of the country for work…… will you be ok with that?

First find out where you may have to relocate and how much travel may be involved. Then respond to the question.

19. Have you discussed about your job with your family?

This is up to you. Be totally honest

20. Why you want to join TCS? or Why do you want to join TCS and not any other company?

Try to speak something about good work environment & growth.

Example : I heard from my friends that TCS has a very good work environment where employees get good respect. Moreover, TCS is one of the Top IT company in India and abroad. I want to be part of Asia’s largest Software Company where I can also grow along with the company. For these reasons, I prefer TCS.
Caution: Never tell the reasons such as ONSITE or SALARY. That gives a negative impression on you.

21. What do you know about TCS as a company?

Best sources for researching your target company: annual reports, the corporate newsletter, contacts you know at the company or its suppliers, advertisements, articles about the company in the trade press.

Tata Consultancy Services Limited (TCS) is an Indian multinational IT services, business solutions and outsourcing company headquartered in Mumbai- India and a subsidiary of the Tata Group conglomerate. It is the largest Asia based provider of business process outsourcing services. TCS has been ranked #20 in the list of top companies of India, by Fortune India 500 magazine. It is the largest IT service company in India by revenue and market capitalization.

TCS has 142 offices across over 42 countries and generates around 30 per cent of India’s IT exports. The company became the first Indian IT company to cross the ten billion dollar milestone posting annual revenues of $10.17 billion.

22.Do you have any questions for me?
Job hunters need to know whether a potential position is a good fit for them professionally and culturally. To do that, they need to find out all they can about a potential employer’s company or department. To help you in this endeavor, here are the questions you should ask during initial job interviews .By taking this list with you to that next job interview , you’ll be able to ask the right question to help you determine whether the company will be a good fit for your talents and expectations.
Why is this position open?
can you explain a typical day in this role?
what is the company policies regarding training ?
would the job description assigned to me be based on my interest area?
could you describe the work culture (do people work time , overtime, etc…)
what are the personal growth opportunities (such as leadership training , company supported community work , mentoring, and so on)?

THese are some TCS HR Interview questions for your preparation for interviews at TCS. Prepare well with these TCS HR Interview questions.



Saturday 23 August 2014

ME 2204 FLUID MECHANICS AND MACHINERY Two Marks Questions With Answers 2014


ME 2204 FLUID MECHANICS AND MACHINERY Two Marks Questions With Answers 2014


SRINIVASAN ENGINEERING COLLEGE, PERAMBALUR-621212

DEPARTMENT OF MECHANICAL ENGINEERING

ME 2204 FLUID MECHANICS AND MACHINERY

TWO MARKS QUESTIONS AND ANSWERS

UNIT I: INTRODUCTION

1. Define density or mass density.

Density of a fluid is defined as the ratio of the mass of a fluid to its volume.

Density, ρ = mass/volume (Kg/m3)

ρwater = 1000 Kg/m3

2. Define specific weight or weight density.

Specific weight or weight density of a fluid is defined as the ratio between the weight of a fluid to its volume.

Specific weight, γ = weight/volume (N/m3)

γ = ρg

γwater = 9810 N/m3

3. Define specific volume.

Specific volume of a fluid is defined as the volume of fluid occupied by an unit wt or unit mass of a fluid.

Specific volume vs = volume/ wt = 1/γ = 1/ρg ----- for liquids

Specific volume vs = volume/ mass = 1/ρ ----- for gases

4. Define dynamic viscosity.

Viscosity is defined as the property of fluid which offers resistance to the movement of one layer of fluid over another adjacent layer of the fluid.

du

δ = μ --------- dy

μ – dynamic viscosity or viscosity or coefficient of viscosity (N-s/m2)

1 N-s/m2 = 1 Pa-s = 10 Poise

5. Define Kinematic viscosity.

It is defined as the ratio between the dynamic viscosity and density of fluid.

ν = μ/ρ (m2/s)

1 m2/s = 10000 Stokes (or) 1 stoke = 10-4 m2/s

6. Types of fluids.

Ideal fluid, Real fluid, Newtonian fluid, Non-Newtonian fluid, Ideal Plastic fluid.

7. Define Compressibility.

It is defined as the ratio of volumetric strain to compressive stress.

Compressibility, β = (d Vol/ Vol) / dp (m2/N)

8. Define Surface Tension.

Surface tension is defined as the tensile force acting on the surface of the liquid in contact with a gas or on the surface between two immiscible liquids such that the contact surface behaves like a membrane under tension.

Surface Tension, σ = Force/Length (N/m)

σwater = 0.0725 N/m σMercury = 0.52 N/m

9. Surface tension on liquid droplet, σ = pd/4

Surface tension on a hollow bubble, σ = pd/8

Surface tension on a liquid jet, σ = pd/2

ζ – surface tension (N/m)

d – diameter (m)

p – pressure inside (N/m2)

ptotal = pinside + patm patm = 101.325 x 103 N/m2

10. Define Capillarity.

Capillarity is defined as a phenomenon of rise or fall of a liquid surface in a small tube relative to the adjacent general level of liquid when the tube is held vertically in the liquid. The rise of liquid surface is known as capillary rise while the fall of liquid surface is known as capillary depression.

Capillary Rise or fall, h = (4σ cosζ) / ρgd

ζ = 0 for glass tube and water ζ = 130º for glass tube and mercury

11. Define Vapour Pressure.

When vaporization takes place, the molecules start accumulating over the free liquid surface exerting pressure on the liquid surface. This pressure is known as Vapour pressure of the liquid.

12. Define Control Volume.

A control volume may be defined as an identified volume fixed in space. The boundaries around the control volume are referred to as control surfaces. An open system is also referred to as a control volume.

13. Write the continuity equation.

The equation based on the principle of conservation of mass is called continuity equation.

δu/δx + δv/δy + δw/δz = 0 ----- three dimensional flow

δu/δx + δv/δy = 0 ----- two dimensional flow

Q = a1v1 = a2v2 ----- one dimensional flow

UNIT II: FLOW THROUGH CIRCULAR CONDUITS

1. List the types of fluid flow.

Steady and unsteady flow Uniform and non-uniform flow Laminar and Turbulent flow

Compressible and incompressible flow

Rotational and ir-rotational flow

One,two and three dimensional flow.

2. Define Steady and Unsteady flow.

Steady flow

Fluid flow is said to be steady if at any point in the flowing fluid various characteristics such as velocity, density, pressure,etc do not change with time.

∂V/∂t = 0 ∂p/∂t = 0 ∂ρ/∂t = 0

Unsteady flow

Fluid flow is said to be unsteady if at any point flowing fluid any one or all characteristics which describe the behaviour of the fluid in motion change with time.

∂V/∂t ≠ 0 ∂p/∂t ≠ 0 ∂ρ/∂t ≠ 0

3. Define Uniform and Non-uniform flow.

Uniform flow

When the velocity of flow of fluid does not change both in direction and magnitude from point to point in the flowing fluid for any given instant of time, the flow is said to be uniform.

∂V/∂s = 0 ∂p/∂s = 0 ∂ρ/∂s = 0

Non-uniform flow

If the velocity of flow of fluid changes from point to point in the flowing fluid at any instant, the flow is said to be non-uniform flow.

∂V/∂s ≠ 0 ∂p/∂s ≠ 0 ∂ρ/∂s ≠ 0

4. Compare Laminar and Turbulent flow.

Laminar and Turbulent flow

A flow is said to be laminar if Reynolds number is less than 2000 for pipe flow. Laminar flow is possible only at low velocities and high viscous fluids. In laminar type of flow, fluid particles move in laminas or layers gliding smoothly over the adjacent layer.

Turbulent flow

In Turbulent flow, the flow is possible at both velocities and low viscous fluid. The flow is said to be turbulent if Reynolds number is greater than 4000 for pipe flow. In Turbulent type of flow fluid, particles move in a zig – zag manner.

5. Define Compressible and incompressible flow

Compressible flow

The compressible flow is that type of flow in which the density of the fluid changes from point to point i.e. the density is not constant for the fluid. It is expressed in kg/sec.

ρ ≠ constant

Incompressible flow

The incompressible flow is that type of flow in which the density is constant for the fluid flow. Liquids are generally incompressible. It is expressed in m3/s.

ρ = constant

6. Define Rotational and Ir-rotational flow.

Rotational flow

Rotational flow is that type of flow in which the fluid particles while flowing along stream lines and also rotate about their own axis.

Ir-rotational flow

If the fluid particles are flowing along stream lines and do not rotate about their own axis that type of flow is called as ir-rotational flow

7. Define One, Two and Three dimensional flow.

One dimensional flow

The flow parameter such as velocity is a function of time and one space co- ordinate only. u = f (x), v = 0 & w = 0.

Two dimensional flow

The velocity is a function of time and two rectangular space co-ordinates.

u = f1(x,y), v = f2(x,y) & w =0.

Three dimensional flow

The velocity is a function of time and three mutually perpendicular directions.

u = f1(x,y,z), v = f2(x,y,z) & w = f3(x,y,z).

8. State the assumptions used in deriving Bernoulli’s equation


Flow is steady;

Flow is laminar;

Flow is irrotational;


Flow is incompressible;

Fluid is ideal.


9. Write the Bernoulli’s equation applied between two sections with losses.

p1/ρg + v2 /2g + Z = p /ρg + v2 /2g + Z + h

1 1 2 2 2 l

10. List the instruments works on the basis of Bernoulli’s equation.

Venturi meter; Orifice meter; Pitot tube.

11. Define Impulse Momentum Equation (or) Momentum Equation.

The total force acting on fluid is equal to rate of change of momentum. According to Newton‟s second law of motion, F = ma

F dt = d(mv)

12. Mention the range of Reynold’s number for laminar and turbulent flow in a pipe.

If the Reynold,s number is less than 2000, the flow is laminar. But if the

Reynold‟s number is greater than 4000, the flow is turbulent flow.

13. What does Haigen-Poiseulle equation refer to?

The equation refers to the value of loss of head in a pipe of length „L‟ due to viscosity in a laminar flow.

14. What is Hagen poiseuille’s formula? (P1-P2) / ρg = hf = 32 µŪL / ρgD2

The expression is known as Hagen poiseuille formula.

Where P1-P2 / ρg = Loss of pressure head, Ū= Average velocity,

µ = Coefficient of viscosity, L = Length of pipe

D = Diameter of pipe,

15. Write the expression for shear stress?

Shear stress δ = - (∂p/∂x) (r/2)

δmax = - (∂p/∂x) (R/2)

16. Give the formula for velocity distribution: -

The formula for velocity distribution is given as

u = - (¼ µ) (∂p/∂x) (R2-r2)

Where R = Radius of the pipe, r = Radius of the fluid element

17. Give the equation for average velocity : -

The equation for average velocity is given as

Ū = - (1/8µ) (∂p/∂x) R2

Where R = Radius of the pipe

18. Write the relation between Umax and Ū?

Umax / Ū = { - (¼ µ) (∂p/∂x) R2 } / { - ⅛µ (∂p/∂x) R2 } Umax / Ū = 2

19. Give the expression for the coefficient of friction in viscous flow?

Coefficient of friction between pipe and fluid in viscous flow f =16/ Re

Where, f = Re = Reynolds number

20. What are the factors to be determined when viscous fluid flows through the circular pipe?

The factors to be determined are:

i. Velocity distribution across the section.

ii. Ratio of maximum velocity to the average velocity. iii. Shear stress distribution.

iv. Drop of pressure for a given length.

21. Define kinetic energy correction factor?

Kinetic energy factor is defined as the ratio of the kinetic energy of the flow per sec based on actual velocity across a section to the kinetic energy of the flow per sec based on average velocity across the same section. It is denoted by (α).

K. E factor (α) = K.E per sec based on actual velocity / K.E per sec based on

Average velocity

22. Define momentum correction factor (β):

It is defined as the ratio of momentum of the flow per sec based on actual velocity to the momentum of the flow per sec based on average velocity across the section.

β= Momentum per sec based on actual velocity/Momentum Per sec based on average velocity

23. Define Boundary layer.

When a real fluid flow passed a solid boundary, fluid layer is adhered to the solid boundary. Due to adhesion fluid undergoes retardation thereby developing a small region in the immediate vicinity of the boundary. This region is known as boundary layer.

24. What is mean by boundary layer growth?

At subsequent points downstream of the leading edge, the boundary layer region increases because the retarded fluid is further retarded. This is referred as growth of boundary layer.

25. Classification of boundary layer.

(i) Laminar boundary layer, (ii) Transition zone, (iii) Turbulent boundary layer.

26. Define Laminar boundary layer.

Near the leading edge of the surface of the plate the thickness of boundary layer is small and flow is laminar. This layer of fluid is said to be laminar boundary layer.

The length of the plate from the leading edge, upto which laminar boundary layer

exists is called as laminar zone. In this zone the velocity profile is parabolic.

27. Define transition zone.

After laminar zone, the laminar boundary layer becomes unstable and the fluid motion transformed to turbulent boundary layer. This short length over which the changes taking place is called as transition zone.

28. Define Turbulent boundary.

Further downstream of transition zone, the boundary layer is turbulent and continuous to grow in thickness. This layer of boundary is called turbulent boundary layer.

29. Define Laminar sub Layer

In the turbulent boundary layer zone, adjacent to the solid surface of the plate the velocity variation is influenced by viscous effects. Due to very small thickness, the velocity distribution is almost linear. This region is known as laminar sub layer.

30. Define Boundary layer Thickness.

It is defined as the distance from the solid boundary measured in y-direction to the point, where the velocity of fluid is approximately equal to 0.99 times the free stream velocity (U) of the fluid. It is denoted by δ.

31. List the various types of boundary layer thickness.

Displacement thickness(δ*), Momentum thickness(θ), Energy thickness(δ**)

32. Define displacement thickness.

The displacement thickness (δ) is defined as the distance by which the boundary should be displaced to compensate for the reduction in flow rate on account of boundary layer formation.

δ* = ∫ [ 1 – (u/U) ] dy

33. Define momentum thickness.

The momentum thickness (θ) is defined as the distance by which the boundary should be displaced to compensate for the reduction in momentum of the flowing fluid on account of boundary layer formation.

ζ = ∫ [ (u/U) – (u/U)2 ] dy

34. Define energy thickness

The energy thickness (δ**) is defined as the distance by which the boundary should be displaced to compensate for the reduction in kinetic energy of the flowing fluid on account of boundary layer formation.

δ** = ∫ [ (u/U) – (u/U)3 ] dy

35. What is meant by energy loss in a pipe?

When the fluid flows through a pipe, it looses some energy or head due to frictional resistance and other reasons. It is called energy loss. The losses are classified as; Major losses and Minor losses

36. Explain the major losses in a pipe.

The major energy losses in a pipe is mainly due to the frictional resistance caused by the shear force between the fluid particles and boundary walls of the pipe and also due to viscosity of the fluid.

37. Explain minor losses in a pipe.

The loss of energy or head due to change of velocity of the flowing fluid in magnitude or direction is called minor losses. It includes: sudden expansion of the pipe, sudden contraction of the pipe, bend in a pipe, pipe fittings and obstruction in the pipe, etc.

38. State Darcy-Weisbach equation OR What is the expression for head loss due to friction?

hf = 4flv2 / 2gd

where, hf = Head loss due to friction (m), L = Length of the pipe (m),

d = Diameter of the pipe (m), V = Velocity of flow (m/sec)

f = Coefficient of friction

39. What are the factors influencing the frictional loss in pipe flow?

Frictional resistance for the turbulent flow is,

i. Proportional to vn where v varies from 1.5 to 2.0. ii. Proportional to the density of fluid.

iii. Proportional to the area of surface in contact.

iv. Independent of pressure.

v. Depend on the nature of the surface in contact.

40. Write the expression for loss of head due to sudden enlargement of the pipe.

hexp = (V1-V2)2 /2g

Where, hexp = Loss of head due to sudden enlargement of pipe.

V1 = Velocity of flow at pipe 1; V2 = Velocity of flow at pipe 2.

41. Write the expression for loss of head due to sudden contraction. hcon =0.5 V2/2g

hcon = Loss of head due to sudden contraction. V = Velocity at outlet of pipe.

42. Write the expression for loss of head at the entrance of the pipe. hi =0.5V2/2g

hi = Loss of head at entrance of pipe. V = Velocity of liquid at inlet of the pipe.

43. Write the expression for loss of head at exit of the pipe. ho = V2/2g

where, ho = Loss of head at exit of the pipe.

V = Velocity of liquid at inlet and outlet of the pipe.

44. Give an expression for loss of head due to an obstruction in pipe

Loss of head due to an obstruction = V2 / 2g ( A/ Cc (A-a ) -1 )2

Where, A = area of pipe, a = Max area of obstruction,

V = Velocity of liquid in pipe A-a = Area of flow of liquid at section 1-1

45. What is compound pipe or pipes in series?

When the pipes of different length and different diameters are connected end to end, then the pipes are called as compound pipes or pipes in series.

46. What is mean by parallel pipe and write the governing equations.

When the pipe divides into two or more branches and again join together downstream to form a single pipe then it is called as pipes in parallel. The governing equations are:

Q1 = Q2 + Q3 hf1 = hf2

47. Define equivalent pipe and write the equation to obtain equivalent pipe diameter.

The single pipe replacing the compound pipe with same diameter without change in discharge and head loss is known as equivalent pipe.

L = L1 + L2 + L3

(L/d5) = (L1/d1 5) + (L2/d2 5) + (L3/d3 5)

48. What is meant by Moody’s chart and what are the uses of Moody’s chart?

The basic chart plotted against Darcy-Weisbach friction factor against Reynold‟s Number (Re) for the variety of relative roughness and flow regimes. The relative roughness is the ratio of the mean height of roughness of the pipe and its diameter (ε/D).

Moody‟s diagram is accurate to about 15% for design calculations and used for a large number of applications. It can be used for non-circular conduits and also for open channels.

49. Define the terms a) Hydraulic gradient line [HGL] b) Total Energy line [TEL]

Hydraulic gradient line: It is defined as the line which gives the sum of pressure head and datum head of a flowing fluid in a pipe with respect the reference line.

HGL = Sum of Pressure Head and Datum head

Total energy line: Total energy line is defined as the line which gives the sum of pressure head, datum head and kinetic head of a flowing fluid in a pipe with respect to some reference line.

TEL = Sum of Pressure Head, Datum head and Velocity head

UNIT III : DIMENSIONAL ANALYSIS

1. Define dimensional analysis.

Dimensional analysis is a mathematical technique which makes use of the study of dimensions as an aid to solution of several engineering problems. It plays an important role in research work.

2. Write the uses of dimension analysis?

• It helps in testing the dimensional homogeneity of any equation of fluid motion.

• It helps in deriving equations expressed in terms of non-dimensional parameters.

• It helps in planning model tests and presenting experimental results in a systematic manner.

3. List the primary and derived quantities.

Primary or Fundamental quantities: The various physical quantities used to describe a given phenomenon can be described by a set of quantities which are independent of each other. These quantities are known as fundamental quantities or primary quantities. Mass (M), Length (L), Time (T) and Temperature (θ) are the fundamental quantities.

Secondary or Derived quantities: All other quantities such as area, volume, velocity, acceleration, energy, power, etc are termed as derived quantities or secondary quantities because they can be expressed by primary quantities.

4. Write the dimensions for the followings.

Dynamic viscosity (μ) – ML-1T-2, Force (F) - MLT-2, Mass density (ρ) – ML-3, Power (P) -ML2T-3

5. Define dimensional homogeneity.

An equation is said to be dimensionally homogeneous if the dimensions of the terms on its LHS are same as the dimensions of the terms on its RHS.

6. Mention the methods available for dimensional analysis.

Rayleigh method, Buckinghum π method

7. State Buckingham’s π theorem.

It states that “if there are „n‟ variables (both independent & dependent variables) in a physical phenomenon and if these variables contain „m‟ functional dimensions and are related by a dimensionally homogeneous equation, then the variables are arranged into n-m dimensionless terms. Each term is called π term”.

8. List the repeating variables used in Buckingham π theorem.

Geometrical Properties – l, d, H, h, etc, Flow Properties – v, a, g, ω, Q, etc, Fluid Properties – ρ, μ, γ, etc.

9. Define model and prototype.

The small scale replica of an actual structure or the machine is known as its Model, while the actual structure or machine is called as its Prototype. Mostly models are much smaller than the corresponding prototype.

10. Write the advantages of model analysis.

• Model test are quite economical and convenient.

• Alterations can be continued until most suitable design is obtained.

• Modification of prototype based on the model results.

• The information about the performance of prototype can be obtained well in advance.

11. List the types of similarities or similitude used in model anlaysis.

Geometric similarities, Kinematic similarities, Dynamic similarities

12. Define geometric similarities

It exists between the model and prototype if the ratio of corresponding lengths, dimensions in the model and the prototype are equal. Such a ratio is known as “Scale Ratio”.

13. Define kinematic similarities

It exists between the model and prototype if the paths of the homogeneous moving particles are geometrically similar and if the ratio of the flow properties is equal.

14. Define dynamic similarities

It exits between model and the prototype which are geometrically and kinematically similar and if the ratio of all forces acting on the model and prototype are equal.

15. Mention the various forces considered in fluid flow.


Inertia force,

Viscous force,

Gravity force,


Pressure force,

Surface Tension force,

Elasticity force


16. Define model law or similarity law.

The condition for existence of completely dynamic similarity between a model and its prototype are denoted by equation obtained from dimensionless numbers. The laws on which the models are designed for dynamic similarity are called Model laws or Laws of Similarity.

17. List the various model laws applied in model analysis.


Reynold‟s Model Law,

Froude‟s Model Law,


Euler‟s Model Law,

Weber Model Law,

Mach Model Law


18. State Reynold’s model law

For the flow, where in addition to inertia force the viscous force is the only other predominant force, the similarity of flow in the model and its prototype can be established, if the Renold‟s number is same for both the systems. This is known as Reynold‟s model law. Re(p) = Re(m)

19. State Froude’s model law

When the forces of gravity can be considered to be the only predominant force which controls the motion in addition to the force of inertia, the dynamic similarities of the flow in any two such systems can be established, if the Froude number for both the system is the same. This is known as Froude Model Law. Fr(p) = Fr (m)

20. State Euler’s model law

In a fluid system where supplied pressures are the controlling forces in addition to inertia forces and other forces are either entirely absent or in-significant the Euler‟s number for both the model and prototype which known as Euler Model Law.

21. State Weber’s model law

When surface tension effect predominates in addition to inertia force then the dynamic similarity is obtained by equating the Weber‟s number for both model and its prototype, which is called as Weber Model Law.

22. State Mach’s model law

If in any phenomenon only the forces resulting from elastic compression are significant in addition to inertia forces and all other forces may be neglected, then the dynamic similarity between model and its prototype may be achieved by equating the Mach‟s number for both the systems. This is known Mach Model Law.

23. Classify the hydraulic models.

The hydraulic models are classified as: Undistorted model & Distorted model

24. Define undistorted model

An undistorted model is that which is geometrically similar to its prototype, i.e. the scale ratio for corresponding linear dimensions of the model and its prototype are same.

25. Define distorted model

Distorted models are those in which one or more terms of the model are not identical with their counterparts in the prototype.

26. Define Scale effect

An effect in fluid flow that results from changing the scale, but not the shape, of a body around which the flow passes.

27. List the advantages of distorted model.

• The results in steeper water surface slopes and magnification of wave heights in model can be obtained by providing true vertical structure with accuracy.

• The model size can be reduced to lower down the cast.

• Sufficient tractate force can be developed to produce bed movement with a small model.

28. Write the dimensions for the followings.


Quantities

Symbol

Unit

Dimension


Area

A

m2

L2


Volume

V

m3

L3


Angle

Α

Deg. Or Rad

M0L0T0


Velocity

v

m/s

LT-1


Angular Velocity

ω

Rad/s

T-1


Speed

N

rpm

T-1


Acceleration

a

m/s2

LT-2


Gravitational Acceleration

g

m/s2

LT-2


Discharge

Q

m3/s

L3T-1


Discharge per meter run

q

m2/s

L2T-1



Mass Density

ρ

Kg/m3

ML3


Sp. Weight or Unit Weight

N/m3

ML-2T-2


Dynamic Viscosity

μ

N-s/m2

ML-1T-1


Kinematic viscosity

m2/s

L2T-1


Force or Weight

F or W

N

MLT-2


Pressure or Pressure intensity

p

N/m2 or Pa

ML-1T-2


Modulus of Elasticity

E

N/m2 or Pa

ML-1T-2


Bulk Modulus

K

N/m2 or Pa

ML-1T-2


Workdone or Energy

W or E

N-m

ML2T-2


Torque

T

N-m

ML2T-2


Power

P

N-m/s or J/s or Watt

ML2T-3


UNIT IV : ROTO DYNAMIC MACHINES

1. What are fluid machines or Hydraulic machines?

The machines which use the liquid or gas for the transfer of energy from fluid to rotor or from rotor to fluid are known as fluid machines.

2. How are fluid machines classified?

Fluid machines are classified into two categories depending upon transfer of energy:

1. Turbines – hydraulic energy is converted to mechanical energy and then electrical energy. 2. Pumps – electrical energy is converted to mechanical energy and then hydraulic energy.

3. What are called turbines?

Hydraulic turbines are the machines which use the energy of water and convert it into mechanical energy. The mechanical energy developed by a turbine is used in running the electrical generator which is directly coupled to the shaft.

4. What is known as Euler’s equation for turbo-machines?

The general expression for the work done per second on impeller is

ρQ[Vw1u1 + Vw2u2]

5. Define Gross Head of a turbine.

The difference between head race level and tail race level is known as Gross Head

6. Define Net head of a turbine.

It is also called effective head and is defined as the head available at the inlet of the turbine. H = Hg – hf

7. What are the efficiencies of a turbine?

Hydraulic efficiency Mechanical efficiency

Volumetric efficiency Overall efficiency

8. Define Hydraulic efficiency.

It is defined as the ratio of the power given by water to the runner of a turbine to the power supplied by the water at the inlet of the turbine.

Power delivered to runner (runner power)

εh = ------------------------------------------------------------ Power supplied at inlet (water power)

Water power = γQH = (1/2) m v2

9. Define Mechanical efficiency.

The ratio of the power available at the shaft of the turbine to the power delivered to the runner is defined as mechanical efficiency.

Power available at the shaft (shaft power)

εm = ------------------------------------------------------------ Power delivered to runner (runner power)

10. Define volumetric efficiency.

The ratio of the volume of the water actually striking the runner to the volume of water supplied to the turbine is defined as volumetric efficiency.

11. Define Overall efficiency.

It is defined as the ratio of the power available at the shaft of the turbine to the power supplied by the water at the inlet of the turbine.

Power available at the shaft (shaft power)

εo = ---------------------------------------------------------- Power supplied at inlet (water power)

εo = εh εm εv (or) εo = εh εm

12. What are an impulse turbine and a reaction turbine? Impulse Turbine:

If at the inlet of the turbine, the energy available is only kinetic energy, the turbine

is known as impulse turbine. The pressure at the inlet of the turbine is atmosphere. This turbine is used for high heads. The water strikes the bucket along the tangent of the runner. Ex: Pelton Wheel Turbine.

Reaction Turbine:

If at the inlet of the turbine, the water possesses kinetic energy as well as pressure energy, the turbine is known as reaction turbine. As the water flows through the runner, the water is under pressure and the pressure energy goes on changing into kinetic energy. The runner is completely enclosed in an air-tight casing and the runner and casing is completely full of water. This turbine is used for medium heads. Ex: Francis Turbine.

13. Define Jet Ratio.

It is defined as the ratio of the pitch diameter (D) of the Pelton wheel to the diameter of the jet (d). It is denoted by „m‟ and is given as m = D/d

14. Classification of hydraulic turbines:

(a) Based on type of energy available at inlet

Impulse turbine (Pelton wheel)

Reaction turbine (Francis turbine, Kaplan turbine, Propeller turbine)

(b) Based on head available at inlet

High head turbine – [ > 250 m ] - (Pelton wheel)

Medium head turbine – [ 60 to 250 m ] - (Francis turbine)

Low head turbine – [ < 60 m ] – (Kaplan turbine, Propeller turbine)

(c) Based on specific speed

High specific speed turbine – (Kaplan turbine, Propeller turbine) Medium specific speed turbine - (Francis turbine)

Low specific speed turbine - (Pelton wheel)

(d) Based on direction of flow through runner

Tangential flow turbine Radial flow turbine

Axial flow turbine Mixed flow turbine

15. Define Radial flow reaction turbine and their types.

If water flows in the radial direction in the turbine then it is referred as radial flow turbine.

Types:

Inward radial flow reaction turbine: If the water flows from outwards to inwards through the runner, the turbine is known as inward radial flow reaction turbine. Here

the outer diameter of the runner is inlet diameter whereas the inner diameter of the

runner is outlet diameter.

Outward radial flow reaction turbine: If the water flows from inwards to outwards through the runner, the turbine is called as outward radial flow reaction turbine. Here the outer diameter of the runner is outlet diameter whereas the inner diameter of the runner is inlet diameter.

16. What is mean by Draft

Tube?

The draft tube is a pipe of gradually increasing area which connects the outlet of the runner to the tail race. One end of the draft tube is connected to the outlet of the runner while the other end is sub-merged below the level of water in the tail race.

17. Why do draft tubes have enlarging passage area in the direction of flow?

The pressure at the exit of the reaction turbine is generally less than atmospheric and this makes the water NOT to discharge directly to the tail race. By the introduction of draft tube, which has enlarged area in the direction of flow, the kinetic head reduces and pressure head increases. There by discharge of water to the tail race safely.

18. Uses of draft tube:

Discharges water to tail race safely

Converts a large proportion of rejected kinetic energy into useful pressure energy

Net head of the turbine is increased.

19. Types of draft tube:

Conical draft tube, Simple elbow tube, Moody spreading tube and Elbow draft tube with circular inlet and rectangular outlet.

20. Define specific speed of a turbine.

It is defined as the speed of the turbine which is geometrically similar and it will develop unit power when working under unit head.

Ns = N √P/ (H)5/4

21. Define Runaway speed of Turbine.

The max speed reached by the turbine after the removal of the external load is called runaway speed of turbine. The various rotating components of the turbine should be designed to remain safe at the runaway speed.

22. List the characteristic curves of Hydraulic turbine.

Main Characteristic Curves (or) Constant Head Curves

Operating Characteristic Curves (or) Constant Speed Curves

23. What is roto dynamic pump?

When the increase in pressure is developed by rotating impeller or by action of centrifugal force then the pump is called as roto dynamic pump.

24. Define Centrifugal pump.

Hydraulic pump means it converts mechanical energy into hydraulic energy. If the mechanical energy is converted into pressure energy means of centrifugal force acting on the fluid, the hydraulic machine is called Centrifugal Pump.

25. Define Specific speed of a centrifugal pump.

The specific speed of a centrifugal pump is defined as the speed of a geometrically similar pump which would deliver 1 m3/s against a head of 1 m.

Ns = N √Q/ (H)3/4 (OR) Ns = N √P/ (H)5/4

26. Efficiencies of a Centrifugal Pump:

Manometric Efficiency:

The ratio of the manometric head to the head imparted by the impeller to the water is known as manometric efficiency.

Manometric Head g Hm

εmano = ------------------------------------------------------- = ----------- Head imparted by impeller to water Vw2u2

Head imparted by impeller to water = Vw2u2/g

Mechanical Efficiency:

The ratio of the power available at the impeller to the power at the shaft of the centrifugal pump is known as mechanical efficiency.

Power at the impeller

εmech = --------------------------------- Shaft Power

Power at the impeller = workdone by impeller per sec = ρQ Vw2u2

Overall Efficiency:

The ratio of power output of the pump to the power input to the pump is called as overall efficiency.

Weight of water lifted x Hm

εo = ------------------------------------------ Shaft Power

27. Define Manometric Head.

The manometric head is defined as the head against which a centrifugal pump has to work.

Hm = head imparted by the impeller to the water – loss of head

Hm = Vw2u2/g - loss of head

Hm = hs + hd + hfs + hfd + vd 2/2g

28. Differentiate static head & manometric head.


Sl. No.

Static Head

Manometric Head


1

The vertical head distance to liquid

surface in sump to overhead tank.

Total head that must be produced

by pump to satisfy the external requirements.


2

Loss of head in the pump is not

considered.

The friction head loss & kinetic head

are considered.


3

H = Hs + Hd

Hm = Hs + Hd + hfd + v 2/2g

d


29. Minimum speed for starting a Centrifugal Pump, Hm = u2 2/2g - u1 2/2g

30. What is mean by multi stage pump?

If more than one impeller is used in pump then such type is known as multistage pump.

Impellers in series – Number of impellers are mounted on a common shaft. This increases the total head. Total head = n Hm

Impellers in parallel – Impellers are mounted in separate shaft. This increases the discharge. Total discharge = n Q

31. Compare Centrifugal Pump & Reciprocating Pump.


Sl. No.

Centrifugal Pump

Reciprocating Pump


1

Its discharging capacity is more.

Its discharging capacity is low.


2

It can be used for lifting highly viscous

liquids.

It can handle only pure water or less

viscous liquids.


3

Its maintenance cost is low.

Its maintenance cost is high.


4

It can be operated at very high speed.

High speed may cause cavitations

and separation.


32. Define Priming of a centrifugal pump.

Priming of a centrifugal pump is defined as the operation in which the suction pipe, casing of the pump and a portion of the delivery pipe up to the delivery valve is completely filled up from outside source with the liquid to be raised by the pump before starting the pump.

33. Define cavitation.

Cavitation is defined as the phenomenon of formation of vapour bubbles of a flowing liquid in a region where the pressure of the fluid falls below its vapour

pressure and the sudden collapsing of these vapour bubbles in a region of higher pressure.

34. What are pump characteristics?

Pump characteristic means the characteristic curves of a pump. Characteristic curves of centrifugal pumps are defined as those curves which are plotted from the

results of a number of tests on the centrifugal pump. These curves are necessary to

predict the behaviour and performance of the pump when the pump is working under different flow rate, head and speed.

UNIT V : POSITIVE DISPLACEMENT MACHINES

1) What is a reciprocating pump?

Reciprocating pump is a positive displacement pump. This means the liquid is first sucked into the cylinder and then displaced or pushed by the thrust of a piston.

2) What is single acting pump and double acting pump?

If the water is in contact with one side of the piston the pump then it is known as single acting reciprocating pump. For one complete revolution one suction stroke and

one delivery stroke occurs.

If the water is in contact with both sides of the piston the pump then it is called double acting reciprocating pump. For one complete revolution two suction strokes and two delivery strokes occurs.

3) What is Discharge through a Reciprocating Pump?

For Single acting Reciprocating Pump: Discharge (QT)=ALN/60

For Double acting Reciprocating Pump: QT =2ALN/60

A=Area of the Cyclinder (m2), L=Length of Stroke (m), N=Speed of Crank (rpm)

4) What is the Workdone by Reciprocating Pump per sec?

For Single acting Reciprocating Pump: Workdone = ρgALN(hs+hd)/60

For Double acting Reciprocating Pump: Work done= 2ρgALN(hs+hd)/60

Where, ρ=Density of Water (kg/m3), A=Area of the Cylinder (m2),

L= Stroke Length (m), N=Speed (rpm), hs, hd=Suction and Delivery head (m).

5) Define slip and % slip.

The difference between the theoretical discharge (QT) and actual discharge (Qact)

is known as slip of the pump.

Slip = QT - Qact

% Slip = [ (QT - Qact)/QT ] x 100

If Qact is more than the QT then slip will be –ive.

If Qact lesser than QT then the slip will be +ive.

6) Define coefficient of discharge of reciprocating pump?

It is defined as the ratio of actual discharge to theoretical discharge of reciprocating pump. Cd=Qa/Qth. If Cd > 1 then –ive slip occurs and if Cd < 1 then +ive slip occurs.

7) Write the expression for pressure head due to acceleration in suction and delivery pipes.

Pressure head due to acceleration in suction pipe, has = (ls/g) (A/as) ω2r Cosωt

Where, ls - length of suction pipe; A – area of piston cylinder,

as – area of suction pipe; ω – angular velocity; r – radius of crank.

Pressure head due to acceleration in delivery pipe, had = (ld/g) (A/ad) ω2r Cosωt

Where, ld - length of delivery pipe; A – area of piston cylinder,

ad – area of delivery pipe; ω – angular velocity; r – radius of crank.

Max pressure head due to acceleration, ha = (l/g) (A/a) ω2r

8) Write the expression for head due to friction in suction and delivery pipes.

Head loss due to friction in suction pipe is, hfs = (4fls/2gds) [ (A/as) ω2r Sinωt ]2

Where, f – coefficient of friction; ls - length of suction pipe; A – area of piston cylinder, as – area of suction pipe; ds – diameter of suction pipe; ω – Angular velocity; r – radius of crank.

Head loss due to friction in delivery pipe is, hfs = (4fls/2gds) [ (A/as) ω2r Sinωt ]2

Where, f – coefficient of friction; ls - length of delivery pipe; as – area of delivery pipe; ds – diameter of delivery pipe;

9) Define indicator diagram?

The indicator diagram for a reciprocating pump is defined as the graph drawn between the pressure head in the cylinder and the distance traveled by the piston for

one complete revolution of the crank.

10) Define ideal indicator diagram?

It is defined as the graph between pressure head in the cylinder and stroke length of the crank under ideal condition is known as ideal indicator diagram.

During the suction stroke, the pressure in the cylinder is below atmospheric

pressure.

During the delivery stroke, the pressure in the cylinder is above atmospheric pressure.

P Delivery stroke

r e

s hd

s

u r e

h Hatm

e

a

d

L = Stroke Length hs

Suction stroke

Stroke Length

11) What is the relation between Work done of a Pump and Area of Indicator

Diagram ?

Work done by the pump is proportional to the area of the Indicator diagram.

12) What is the Work done by the Pump per sec due to acceleration and friction in the suction and delivery Pipes?

For single acting : Workdone/sec = ρgALN(hs+hd+0.67hfs+0.67hfd)/60

For Double acting : Workdone/sec = 2ρgALN(hs+hd+0.67hfs+0.67hfd)/60

Where, hfs, hfd =loss of head due to friction in suction and delivery pipes.

13) What is an air vessel?

An air vessel is a closed chamber containing compressed air in the top portion and liquid at the bottom of the chamber. At the base of the chamber there is an

opening through which the liquid may flow into the vessel or out from the vessel. When the liquid enters the air vessel, the air gets compressed further and when the liquid flows out of the vessel, the air will expand into the chamber.

14) What is the purpose of an air vessel fitted in the pump?

o To obtain a continuous supply of liquid at a uniform rate.

o To save a considerable amount of work in overcoming the frictional

resistance in the suction and delivery pipes, and

o To run the pump at a high speed with out separation.

15) What is the work saved by fitting an air vessel in a single acting, double acting pump?

Work saved by fitting air vessels in a single acting pump is 84.87%, In a

double acting pump the work saved is 39.2%.

16) Define Cavitation.

If the pressure in the cylinder is below the vapour pressure, the dissolved gases will be liberated from the liquid and air bubbles are formed. This process is termed as cavitaion.

17) Define separation pressure and separation pressure head.

Due to caviation process the continuous flow of fluid will get affected and separation takes place. The pressure at which separation takes place is known as separation pressure and the head corresponding to separation pressure is called separation pressure head.

For water the limiting value of separation pressure head is,

hsep = - 7.8 m (Gauge pressure)

hsep = 10.3 – 7.8 = 2.5 m (Absolute pressure)

18) How will you obtain the maximum speed during suction stroke?

The absolute pressure head will be minimum at the beginning of suction stroke. Thus, in the cylinder the separation taking place at the beginning of suction stroke only. In this case, the absolute pressure head will be equal to the separation pressure.

hsep = Hatm – (hs + has) [or] has = Hatm – hs – hsep

But maximum pressure head due to acceleration in suction pipe is ,

has = (ls/g) (A/as) ω2r

Equating both the angular velocity(ω) and Speed (N) are obtained. This

N is the maximum speed of the pump during the suction stroke without separation.

19) How will you obtain the maximum speed during delivery stroke?

The absolute pressure head will be minimum at the end of delivery stroke. Thus, in the cylinder the separation taking place at the end of delivery stroke only. In this case, the absolute pressure head will be equal to the separation pressure.



hsep = Hatm + hs - had [or] had = Hatm + hd – hsep

But maximum pressure head due to acceleration in delivery pipe is ,

had = (ld/g) (A/ad) ω2r

Equating both the angular velocity (ω) and Speed (N) are obtained. This N is the maximum spped of the pump during the delivery stroke without separation.

20) What is mean by Maximum speed of a Reciprocating Pump?

The maximum speed at which no separation flow is taking place in the cylinder is called maximum speed of a reciprocating pump. It will be the least value of speeds obtained from maximum speed during suction stroke and maximum speed

during delivery stroke.

21) Write the workdone saved by fitting the air vessel in reciprocating pump.

By fitting the air vessel the head loss due to friction in suction and delivery pipe is reduced. This reduction in the head loss saves a certain amount of energy.

Therefore, the workdone saved is given by,


Workdone saved by

workdone against friction

workdone against


friction

Fitting airvessel

without airvessel

with airvessel


22) Write the formula for workdone against friction with air vessel in reciprocating pump.

Workdone against friction with airvessel = [K/π] ρgQ [4fl/2gd] [(A/a) ωr]2

Where, K = 1 for single acting reciprocating pump K = 2 for double acting reciprocating pump Q = theoretical discharge (m3/s)

Q = ALN/60 for single acting reciprocating pump

Q = 2ALN/60 for double acting reciprocating pump f = coefficient of friction

l = length of pipe (m)

d = diameter of pipe (m) A = area of piston (m2)

a = area of pipe (m2)

ω = angular velocity (rad/s)

ω = 2πN/60

r = radius of crank

23) What will be the total % work saved by fitting the air vessel?

For single acting reciprocating pump = 84.8 % For double acting reciprocating pump = 39.2 %