Showing posts with label Fluid Mechanics Lab. Show all posts
Fluid Mechanics Lab
To determine the velocity of fluid flowing through the circular tube using a pitot tube
(Pitot Tube Apparatus)
What is a Pitot Tube?
ØA Pitot tube, also known as Pitot probe, is a pressure measurement instrument used to measure fluid flow velocity.The pitot tube was invented by the French engineer Henri Pitot in the early 18th century. It is widely used to determine the airspeed of an aircraft, water speed of a boat, and to measure liquid, air and gas flow velocities in certain industrial applications.
The pitot tube is used to measure the local flow velocity at a given point in the flow stream and not the average flow velocity in the pipe or conduit.
Working Operation:
uThe basic pitot tube consists of a tube pointing directly into the fluid flow. As this tube contains fluid, a pressure can be measured; the moving fluid is brought to rest (stagnates) as there is no outlet to allow flow to continue. This pressure is the stagnation pressure of the fluid, also known as the total pressure or (particularly in aviation) the pitot pressure.
uThe measured stagnation pressure cannot itself be used to determine the fluid flow velocity (airspeed in aviation). However, Bernoulli's equation states:
Stagnation pressure = static pressure + dynamic pressure
Apparatus: Pitot tube apparatus
Procedure:
1. Place the pitot tube apparatus on the hydraulic bench.
2. Attach the pitot tube with hydraulic bench using pipe and quick release connectors.
3. Start the pump, and admit water to the tube by opening the flow control valve. adjust the flow rate in the tube using the flow control valve of apparatus and hydraulic bench simultaneously so that there are no air bubbles within the tube.
4. Change the flow rate and get different values.
5. For each flow rate allow conditions to become steady, measure and record h1 (static head) and h2 (stagnation head).
Fluid Mechanics Lab
To compute the Reynolds’s Number and to observe the Laminar, Transitional and Turbulent Flow
(Osborne Reynolds’s Demonstration Unit)
Theoratical Background.
Reynold’s No:
ØThe Reynolds number (Re) is an important dimensionless quantity in fluid mechanics used to help predict flow patterns in different fluid flow situations.
ØIt is the ratio of inertial forces to viscous forces within a fluid which is subjected to relative internal movement due to different fluid velocities.
ØIt is used to predict the transition from laminar to turbulent flow.
Ølaminar flow occurs at low Reynolds numbers, where viscous forces are dominant, and is characterized by smooth, constant fluid motion.
turbulent flow occurs at high Reynolds numbers and is dominated by inertial forces, which tend to produce chaotic eddies, vortices and other flow instabilitie.
Procedure:
1. Lower the dye injector until it is seen in the glass tube.
2. Open the inlet valve and allow water to enter stilling tank.
3. Ensure a small overflow spillage through the over flow tube to maintain a constant level.
4. Allow water to settle for a few minutes.
5. Open the flow control valve fractionally to let water flow through the visualizing tube.
6. Slowly adjust the dye control needle valve until a slow flow with dye injection is achieved.
7. Regulate the water inlet and outlet valve until an identifiable dye line is achieved.
8. Measure the flow rate using volumetric method i-e collect the water from the outlet having
die in it in a volumetric tank and calculate the time with a stop watch.
9. Repeat the experiment by regulating water inlet and outlet valve to produce different flows
Fluid Mechanics Lab
 Experiment no 2 |
2. Viscometer.pptx
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To Determine The Viscosity of Fluid Using Viscometer (Find The Viscosity of SAE-30 Lubrication Oil)
Viscometer:A viscometer (also called viscosimeter) is an instrument used to measure the viscosity of a fluid.It is used for those fluids whose viscosity does not change under varying flow conditions.
Rheometers must be used when the viscosity does change with flow conditions.
Viscometers usually work by comparing a stationary object and a fluid flow, or vice versa. Hence, a viscometer could be placed in a fluid flow or moved through a stationary fluid.
The flow must have a Reynolds number in the laminar region in order to record accurate values. The measure of the resistance is taken by measuring the drag resistance during relative motion through the fluid
ØThe viscometer consists of a rotating inner cylinder mounted on a vertical spindle at the top and free at the bottom.
ØThis inner cylinder is hollow and rotates inside another fixed outer cylinder of a larger diameter as shown in Fig.
ØThe space between the outer and inner cylinders is filled with the liquid for which the viscosity is to be measured.
ØThe inner cylinder is rotated by means of a vertically falling weight, which imparts rotational motion to the cylinder by using a pulley and a cord arrangement.
For a given weight, W, the speed of rotation of the inner cylinder is higher when the viscosity of the fluid is lower and vice versa.
Apparatus: Viscometer
Procedure: 1. Insert the fluid in the outer cylinder of unknown viscosity.
2. Attach the first weight (W = 100 grams) to the cord. This weight is the sum of the weight of the pan and the weight in the pan.
3. Release the brake and measure the time elapsed to hit the ground.
4. Note the distance covered by the pan.
5. Repeat the above procedure for the other four weights.
6. The viscosity of the fluid is now the average of the five values obtained from the above steps.
2. Attach the first weight (W = 100 grams) to the cord. This weight is the sum of the weight of the pan and the weight in the pan.
3. Release the brake and measure the time elapsed to hit the ground.
4. Note the distance covered by the pan.
5. Repeat the above procedure for the other four weights.
6. The viscosity of the fluid is now the average of the five values obtained from the above steps.
Fluid Mechanics Lab
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| Bourden Tube Experiment |
1. Dead Weight Calibrator.pptx
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To Calibrate a Bourdon Type Pressure Gauge Using a Dead Weight Pressure Gauge Calibrator
Theoretical Background
1. Calibration: To check error with comparison to some standard device is called calibration.
2. Absolute Pressure (Pabs): The pressure that is taken with reference to absolute zero is called absolute pressure, and at absolute zero there is a perfect vacuum.
3. Gauge Pressure (Pg): The pressure that is taken with reference to atmospheric pressure is called gauge pressure. It may be positive or negative depending upon whether we take (Pg) above the atmospheric pressure or below the atmospheric pressure. Gauge pressure is always measured with atmospheric pressure, that is why when gauge pressure is at atmospheric pressure it results zero.
Pabs = Patm + Pgau
Bourdon Tube Pressure Gauge:
uThe bourdon tube pressure gauge is the most common type used to measure fluid pressure because it is reliable, inexpensive and relatively simple.
uThe bourdon tube is a curved tube closed at one end, which is attached to a spring-loaded mechanism that is itself attached to the gauge’s needle.
uThe port of the gauge is attached to the location in the system where you’re measuring pressure.
As pressure increases within the bourdon tube, the metal tube starts to straighten, and as it does, it tugs on the lever attached to the needle.
Apparatus: Dead Weight Tester
Procedure:
1. Remove the piston from unit.2. Close valve V1 and open valve V2.
3. Fill cylinder with oil.
4. Now close valve V2.
5. Put piston back in position with V1 and V2 in close position.
6. Read out pressure value on gauge and compare it with theoretical results.
7. Repeat the experiment by adding weights.
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