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Lab Session No Objective

This document describes an experiment to investigate the force exerted by a water jet on different target shapes. The equipment includes a hydraulic bench with a nozzle and interchangeable flat, cone, and hemisphere shaped targets. Theoretical expressions predict the force will be greatest on a hemisphere, followed by a cone, with the least force on a flat target due to deflection of the jet. The procedure measures the water volume and time needed to counteract hanging weights and calculates flow rate, velocities, and experimental force values for each target. Results are recorded in a table and compared to theoretical predictions.

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vj kumar
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574 views4 pages

Lab Session No Objective

This document describes an experiment to investigate the force exerted by a water jet on different target shapes. The equipment includes a hydraulic bench with a nozzle and interchangeable flat, cone, and hemisphere shaped targets. Theoretical expressions predict the force will be greatest on a hemisphere, followed by a cone, with the least force on a flat target due to deflection of the jet. The procedure measures the water volume and time needed to counteract hanging weights and calculates flow rate, velocities, and experimental force values for each target. Results are recorded in a table and compared to theoretical predictions.

Uploaded by

vj kumar
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as DOCX, PDF, TXT or read online on Scribd
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Lab Session No

Objective:
To demonstrate and investigate the validity of theoretical expressions for the calculation of the
force exerted by a jet on objects of various shapes.

.Equipment Required:

Following equipment is required to perform this experiment

 HB 100 Hydraulic Bench


 HB 020 Impact of a Jet
 A stopwatch (To determine flow rate)

Technical Data:
Technical data associated with apparatus is given as follows;

 Cylinder diameter: 150 mm.


 Nozzle diameter: 7 mm.
 Target plate diameter: 36 mm.
 Target plates: Flat, 120° inward cone, 180° hemisphere, 120° outward cone.
 Nozzle and target plate material: Plastics.
 Weights: 1 lot total 7.4 N.
Apparatus Diagram:

1
Equipment Set Up:

Place the apparatus on the Hydraulic Bench. Connect the water supply from the Hydraulic
Bench to the test pipe inlet. Adjust the equipment to a level position by using adjustable supports
so that the water jet is vertical, noticing bull’s eye level.
Changing of the target plate.

 Unscrew the wing nuts on the small top flange holding target plate stem.
 Unscrew the target plate from the stem, screw the new target plate until it is hand tight.
 Put the small top flange back on the main apparatus.

Theory:
When a water jet of velocity V0 hits a target plate, its velocity will change direction to V1 as in
Figure

Assume the jet flow rate is m. kg/sec along the X (vertical axis) with V0 m/sec. After striking the
target the jet velocity becomes V1 m/sec and its direction deviate from the original direction by
angle .

Momentum of jet before hitting the target plate = m. V0 kg-m/ sec 2

Momentum of jet after hitting the target plate = m. V1 cos θ kg-m/ sec 2

This impact force = change in momentum

= m. V1 cos θ kg-m/ sec 2 - m. V0 kg-m/ sec 2

= Newton

2
Reaction F by the target plate

F = m. (V0 –V1 cos θ) Newton N = kg-m/ s2

Reaction F for various target are

F on Flat target:

 = 90 degree, cos θ = 0

FF = m. V0 Newton

F on 120° cone target:

 = 120 degree, cos θ = - 0.5

Assume very little energy loss between nozzle and target

V0 = V1

FC = m. V0 [ 1−(−0.5) ] = 1.5 m. V0 Newton

F on hemisphere target:

 = 180 degree, cos θ = -1

FH = m. V0 [ 1−(−1 ) ]

= 2 m. V0 Newton or 2 times that of flat target.

Procedure
The procedure to do the experiment is as following
1. Place a 100 gram weight on the weight support disc which will cause the rod stem to
lower itself.
2. Spin the rod to minimize the friction effect. This is zero water impact.
3. Open the Hydraulics Bench control valve to allow the jet of water to hit the target. When
the target is floating, spin the shaft to minimize the friction effect and at the same time
adjust the flow until the stem rises to its original level marked by pointer.
4. Record the volume and time of the measuring tank.
5. Repeat steps with increased weights.
6. Repeat steps for other types of target plates. The plates are designed such that heights
above nozzle are the same for all targets.

3
Results:
Target Plate Water Time Q Mass Flow rate Velocity at Velocity at Experimental
Vol. ṁ Nozzle target plate force
kg/s V, m/s Vo, m/s
L s L/s N
1.

2.

3.

All results should be recorded as follows

Note: Water volume 1 liter (l) = 1 kg of water (Approximation value)

Comments:

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