Experiment- To determine the coefficient of impact for vanes. Experiment To determine the coefficient of discharge of an orifice meter.

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Aubrey Holland
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SUBJECT: FLUID MECHANICS VIVA QUESTIONS (M.E 4 th SEM) Experiment- To determine the coefficient of impact for vanes. Q1. Explain impulse momentum principal. Ans1.

1 SUBJECT: FLUID MECHANICS VIVA QUESTIONS (M.E 4 th SEM) Experiment- To determine the coefficient of impact for vanes. Q1. Explain impulse momentum principal. Ans1. Momentum equation is based on Newton s second law of motion which states that the algebraic sum of external forces applied to control volume of fluid in any direction is equal to the rate of change of momentum in that direction. Q2. Define discharge. Ans2. Rate of flow is known as discharge. Its unit is m 3 /sec. Q3. What do you mean by impact of jet. Ans3. Impact of jet means the force exerted by the jet on the plate which may be stationary or moving. Experiment To determine the coefficient of discharge of an orifice meter. Q 1. Write down the pressure measuring instruments. Ans 1. The pressure of fluid is measured by manometer and mechanical gauges. Manometer are defined as the devices used for measuring the pressure at a point in a fluid by balancing the column of fluid by the same or another column of the fluid. They are classified as (a) simple manometer (b) differential manometer Mechanical gauges - Mechanical gauges are defined as the devices used for measuring the pressure by balancing the fluid column by the spring or dead weight. Q 2. What is absolute pressure? Ans 2. It is defined as the pressure which is measured with reference to absolute vacuum pressure. Q 3. What is gauge pressure? Ans 3. It is defined as the pressure which is measured with reference to atmospheric pressure. Q 4. What is an orifice meter? Ans 4. It is a device used for measuring the rate of flow of a fluid through a pipe. It consists of a flat circular plate which has a circular sharp edged hole called orifice, which is concentric with the pipe. The orifice diameter is kept generally 0.5 times the diameter of the pipe, though it may vary from 0.4 to 0.8 times the pipe diameter.

Q 5. Define coefficient of discharge. Ans 5. It is the ratio of actual discharge to the theoretical discharge. We will use the device having high value of coefficient of discharge in our flow.

2 Q 5. Define coefficient of discharge. Ans 5. It is the ratio of actual discharge to the theoretical discharge. We will use the device having high value of coefficient of discharge in our flow. Experiment To determine the coefficient of discharge of a venturimeter. Q 1. What is Venturimeter? Ans 2. It is a device used for measuring the rate of flow of a fluid through a pipe. It consists of three parts 1.) a short conversing part 2.) Throat 3.) Diverging part Q 2. Compare orifice meter and venturimeter. Ans 2. (1) Orifice meter is a cheaper device as compared to venturimeter due to its simple design. (2) It requires less space as compared to venturimeter. (3) C d of orifice meter is less than the venturimeter. Q 3. Why C d of venturimeter is higher than the orifice meter. Ans 3. In venturimeter there is no sudden pressure drop due to its structural design, Thus the problem of cavitation does not occur in venturimeter but occurs in orifice meter. That s why C d of venturimeter is higher than the orifice meter. Q 4. What is cavitation? Ans 4. It is the phenomenon of formation of vapour bubbles of a flowing liquid in a region where the pressure of the liquid falls below the vapour pressure and sudden collapsing of these vapour bubbles in a region of higher pressure.when the vapour bubbles collapse a very high pressure is created. The metallic surface is subjected to these high pressures, which cause pitting action on the surface and the metallic surfaces get damaged. Experiment To determine the coefficient of discharge of a notch. Q 1. What is notch and weir? Ans 1. These are the devices which are used for discharge measurement in case of open channel flow.

3 Q 2. What is difference between notch and weir? Ans 2. A notch a generally made of metallic plate while the weir is made of a concrete structure. Q 3. What is difference between open channel flow and close channel flow? Ans 3. In open channel flow the atmospheric pressure is present on the free surface of water while in close channel flow the water flow under pressure more than the atmospheric pressure. Experiment To determine the coefficient of discharge, velocity &contraction of an orifice. Q 1. What is an orifice? Ans 1. Orifice is a small opening of any cross-section on the side or at the bottom of a tank, through which a fluid is flowing. Q 2. What is mouthpiece? Ans 2. A mouthpiece is a short length of a pipe which is two to three times its diameter in length, fitted in a tank or vessel containing the fluid.orifices as well as mouthpieces are used for measuring the rate of flow of fluid. Q 3. What is vent contracta point? Ans 3. It is a point where the area of the jet contracted. Q 4. Define hydraulic coefficients. Ans 4. There are three hydraulic coefficients Coefficient of discharge (C d ), coefficient of velocity (C v ) and coefficient of contraction (C c ) Coefficient of discharge (C d ) it is the ratio of actual discharge to the theoretical discharge. Coefficient of velocity (C v ) it is the ratio of actual velocity of a jet of liquid at vena- contracta and the theoretical velocity of the jet. Coefficient of contraction (C c ) It is the ratio of the area of the jet at vena contracta to the area of the orifice. Experiment To determine the minor losses due to various pipe fittings. Q 1. What are the various minor head losses? Ans 1. Various minor head losses a) Head losses due to sudden enlargement b) Head losses due to sudden contraction

4 c) Head losses due to an obstruction d) Head loss at the entrance of the pipe e) Head loss at the exit of the pipe f) Head loss due to bend in the pipe g) Head loss due to various pipe pitting In case of long pipe the above losses are small as compared to the loss of head due to friction and hence they are called minor losses. Q 2. What is equivalent pipe? Ans 2. It is defined as the pipe of uniform diameter having loss of head and discharge equal to the loss of head and discharge of a compound pipe consisting of several pipes of different lengths and different diameters. Experiment To verify Bernoulli s theorem experimentally. Q 1. State Bernoulli s theorem and write down its assumption. Ans 1. It states that in a steady, ideal flow of incompressible fluid, the total energy at any point of the fluid is constant. The energy consists of pressure energy, kinetic energy and potential energy or datum energy. Assumptions a) the fluid is ideal, b) the flow is steady, c) the flow is incompressible, d) the flow is Irrotational. Q 2. Write down three heads used in Bernoulli s theorem. Ans 2. P/ρg = pressure head or pressure energy per unit weight. V 2 /2g = Kinetic head or kinetic energy per unit weight Z = Potential head or potential energy per unit weight Experiment To find the critical Reynolds s number for a pipe flow. Q 1. Explain different types of fluid flow. Ans 1. Different types of flow are - a) Steady and unsteady flow - A steady flow is one in which the conditions (velocity, pressure and density) DO NOT change with time. Unsteady: An unsteady flow is one in which the conditions (velocity, pressure and density) change with time.

5 b) Uniform and non uniform flow - A uniform flow is one in which the conditions (velocity, pressure and density) DO NOT change with space. A nonuniform flow is one in which the conditions (velocity, pressure and density) change with space. c) Laminar and turbulent flow flow in which fluid particles moves along well- defined paths or stream line and all the stream lines are straight and parallel, it is called laminar flow. Turbulent flow is that type of flow in which the fluid particles move in a zig zag way. Due to movement of fluid particals in a zig-zag way, the eddies formation takes place which are responsible for high energy loss. d) Compressible and incompressible flow compressible flow is that type of flow in which the density of the fluid is not constant. Incompressible flow is that type of flow in which the density of the fluid is constant Q 2. What is Reynolds s number? Write down its significance. Ans 2. Reynolds s number ( Re ) = Ρvd/μ, it is used to determine whether the flow is laminar or turbulent Laminar flow: Re < 2000 Transitional flow: 2000 < Re < 4000 Turbulent flow: Re > 4000 Experiment To determine the variation of friction factor f in different pipe flow. Q 1. What is the reason behind the major head losses? Ans 1. Major head losses are due to friction. Q 2. Write down Darcy - weisbach's equation used for finding major head losses. Ans 2. - Darcy - weisback's equation = 4FLV 2 /d*2g Where f is coefficient of friction, L is length of pipe, V is velocity through pipe, d is diameter of the pipe and g is acceleration due to gravity.

6 Experiment To study the phenomenon of cavitation. Q 1. What is cavitation? Ans 1. It is the phenomenon of formation of vapour bubbles of a flowing liquid in a region where the pressure of the liquid falls below the vapour pressure and sudden collapsing of these vapour bubbles in a region of higher pressure.when the vapour bubbles collapse a very high pressure is created. The metallic surface is subjected to these high pressures, which cause pitting action on the surface and the metallic surfaces get damaged. Q 2. Why C d of venturimeter is higher than the orifice meter Ans 2. In venturimeter there is no sudden pressure drop due to its structural design, Thus the problem of cavitation does not occur in venturimeter but occurs in orifice meter. That s why C d of venturimeter is higher than the orifice meter. Q 3. What are the effects of cavitation? Ans 3. The following are the effects of cavitation a) The metallic surfaces are damaged and cavities are formed on the surface. b) Due to sudden collapse of vapour bubble considerable noise and vibrations are produced. c) The efficiency of turbine decreases due to cavitation. Due to pitting action the surface of the turbine blades becomes rough and the force exerted by the water on the turbine blade decreases. Hence the work done by the water on the runner becomes less and thus efficiency decreases. Q 4. What are the precautions against cavitation? Ans 4. The following precautions should be taken against cavitation - a) The pressure of the flowing liquid in any part of the hydraulic system should not be allowed to fall below its vapour pressure. b) Cavitation resistant materials such as aluminum - bronze and stainless steel should be used.

EXPERIMENT No.1 FLOW MEASUREMENT BY ORIFICEMETER

EXPERIMENT No.1 FLOW MEASUREMENT BY ORIFICEMETER 1.1 AIM: To determine the co-efficient of discharge of the orifice meter 1.2 EQUIPMENTS REQUIRED: Orifice meter test rig, Stopwatch 1.3 PREPARATION 1.3.1