Rehans Fm Lab Report Term.docx

Experiment Statement: To study the profile of free and forced vortex. Objectives of experiment:  To obtain the depth profile in a forced vortex flow.  To obtain the surface profile in a forced vortex flow. Related Theory:  Stream line: Mainly there are three types of stream flow. 1. Linear 2. Turbulent 3. Vortex Forced vortex flow: When water flows out of a vessel through a central hole in the base, a free vortex is formed, the degree of rotation being dependent in initial disturbance. The water moves spirally towards the center with stream line in motion, so that, neglecting losses caused by viscosity, the energy per unit mass remains constant. If, while the mass is rotating, the central hole is plugged. Free Vortex flow: Forced vortex flow can be generated by rotating a cylinder containing water about its axis. Under steady conditions, each particle will move with the same angular velocity and there will not be any relative motion between fluid particles. Streamlines for such a flow will be concentric circles and the total energy is constant along a streamline butvaries from one streamline to another.

Apparatus:  The unit essentially consists of the following parts:  Two way ball valve Radius & Height gauge  Inlet or outlet Height Gauge  Tangential Inlet Clear Acrylic Tank  Base Plate Interchangeable bottom outlet  Inlet Connection Globe Valve

(A)Forced Vortex Procedure: 1. Cylinder is filled with water to a height lower than its half. 2. Cylinder is rotated with a constant speed until a parabolic free surface is formed. Note the speed of rotation now. 3. After steady state conditions are achieved, surface profile readings are taken by measuring 4. Different radiuses and the corresponding heights. The surface elevation at r=0 is taken as the datum for all these readings. i. Repeat the same procedure for two more speeds of rotation.

Observations & Calculations: Height=Hmax=138mm Radius= 12 mm Time= 40 sec

N= 20 rev/min Volume=9 liters Q=1*10-4m3/s

Table is given in which all the recorded values are written.

Radius (mm) Height (mm)

0

30

50

70

90

110

0

1.69

4.7

9.2

15.2

22.7

graph :

Forced vortex Graph 22.7

25 20

15.2 h(mm)

15 9.2

10

Free & Forced vortex Graph

4.7 5

  -100 

0

1.69

0 -50

0

50 r(mm)

100

150

Results:

1. 2. 3. 4. 5.

 For all the values of speed plots obtained are prefect parabolas.  The plots also show the theoretical values and the total head count which also shape of parabolas. Precautions: Always keep apparatus free from dust. Frequently Grease/Oil the rotating parts, once in three months. Always Use Clean Water. If the Apparatus is not in use for more than one month, drain the apparatus completely, and fill pump with cutting oil. (B)Free Vortex When water flows out of a vessel through a central hole in the base, a free vortex is formed, the degree of rotation being dependent in initial disturbance. The water moves spirally towards the center with stream line in motion, so that, neglecting losses caused by viscosity, the energy per unit mass remains constant. If, while the mass is rotating, the central hole is plugged, the flow of water in the vertical plane ceases and the motion becomes one of simple rotation in the horizontal plane, and is known as free cylindrical vortex. Some more examples of free vortex flow are: Flow of liquid through a hole provided at the bottom of the container. Flow of liquid around a circular bend in a pipe. A whirlpool in a river. Flow of fluid in a centrifugal pump casing.

Procedure: 1. Apparatus is cleaned and made dust free and then drain valves are closed. 2. The tank is filled to ¾ of its height and then the open flow control valve is opened. 3. All switches are checked to be on OFF position. 4. Now main power supply and pump are switched ON. 5. Flow control valve is now operated and the orifice at the bottom of the tank is opened so that the water can be discharged outside at a steady rate. 6. Now surface profile readings are taken when steady state is reached and surface elevation at r=0 is taken as the datum for all these readings. Observations & Calculations: Number of revolutions = 58 1minute

time=

ω= 2πN/60 Formula for calculations of heights of points on the surface of vortex is: ℎ= Radius(mm) 0 Height(mm) 2

30 15.7

𝑤2𝑟2 2𝑔

50

70 18 22

90 26

110 29

35

Free Vortex Graph

29

30

26

25

18

22

20

15.7

15 10

Free Vortex Graph

5 2 0 -100

-50

0

50

100

150

Results: 1. The surface profile is shown clearly by the plot. Precautions: 1. Dust free apparatus should be ensured. Clean water should be used. Oiling and greasing of the parts should be done at regular intervals.

Impact of jet experiment Principle: An experiment to to perform the Impact of Jet. Objectives: (1). This experiment is performed to examine the impact of jet on different targets. (2). This experiment is used to find the force exerted by the jet on different targets. Related Theory:  Impact of Jet Apparatus:

An apparatus to allow students to investigate the forces produced by a water jet striking a flat or a curved surface. To understand correctly how a turbine (a Pelton wheel for example) works, students need to understand how jet deflection produces a force on turbine vanes. They also need to know how this force affects the rate of momentum flow in the jet. The 120-Degree Conical Plate and 30- Degree Angled Plate (H8a) are available separately. Impact of jet apparatus comprises a transparent cylinder containing a vertically tapered nozzle and a test plate. The cylinder is on legs and mounts on the top of the hydraulic bench. The nozzle, supplied by the hydraulic bench, produces a highvelocity jet of water which hits the test plate. The test plate connects to a weigh beam assembly with jockey weight which measures the jet force. A drain tube in the base of the cylinder directs water back into the hydraulic bench, allowing accurate flow rate measurement. All test plates are all easily interchangeable, taking only a few seconds and needing no tools. To perform experiments, students level the apparatus and zero the weigh beam assembly. They set the flow from the hydraulic bench to maximum, and measure the jet force. They reduce the flow from the hydraulic bench in several increments. At each increment they record the force of the jet on the plate and the flow rate. They then repeat the experiments for different test plates. Students compare their experimental results to those calculated from theory.

Hydraulic Tank: Hydraulic bench is a very useful apparatus in hydraulics and fluid mechanics. It is involved in majority of experiments to be conducted e.g. To find the value of the co-efficient of velocity ‘Cv’, coefficient of discharge ‘Cd’, to study the characteristics of flow over notches, to find metacentric height, to find head losses through pipes, to verify Bernoulli’s theorem etc. Followings are the parts of hydraulic bench. (1). Centrifugal pump (2). Sump Tank (3). Vertical pipe (4). Control valve (5). Connecter (6).Channel (7).Drain Valve (8).Side Channels (9).Drain Valve (10). Dump valve Procedure:  First of all set the impact of jet apparatus on the hydraulic bench.  Diameter of the nozzle is 8mm.  First target which is for measuring the impact of jet on it is 30 degree tilted.  Measure the distance between the jet and the target.  Switch on the hydraulic pump, opened discharge valve and applied the discharge of 0.0003436m^3/s.



   

The water will strike the target and it will move upward. Loads are applied from upward and the jet is pushed down to its original height from nozzle. Measured the weights applied and examined the force exerted by the jet on the target. Then calculated the theatrical force by using the equation Fth=ρQvi(1-cosϴ) Then repeated the experiment for other targets (90 o, 120o and 180o). Plotted the data in table.

Observations & Calculations: We have calculated the experimental and theoretical results and eliminated them in the form of tables. Targ Volume Time( Q(m3/s) Mass( Fexp=m Fth=pQvi( %age et (l) s) Vn(m/s g) g 1-cosѲ) differen ce 30o 5 14.44 0.0003 150 0.38 0.32 2.5% 45 6.87 o 90 5 14.44 0.0003 250 2.5 2.4 4.1% 45 6.87 o 180 5 14.44 0.0003 450 4.5 4.75 5.26% 45 6.87 120o 5 14..44 0.0003 360 3.5 3.57 1.9% 45 6.87 Precautions: (1) Weights are applied until the target comes to its original height. (2) Discharge is applied at a constant rate during target.