IMPACT OF JET

INTRODUCTION:

Fluid in motion is capable of developing forces that can be importance to the engineer. Knowledge on force exerted by fluid in motion is essential in order to analyze fluid flow problems related to the hydraulic machines such as turbines and pumps, force on pipe bends and forces exerted by a hydraulic pump.

Newton’s second law states that force is equal to mass multiplied by acceleration, example:

F = ma

OBJECTIVES:

The objectives of this experiment are:

1. To measure the force produced by a jet on a flat and curved surfaces.

2. To compare the experimental results with the theoretically calculated values.

APPARATUS:

1. level gauge

2. spring

3. weight pan

4. sprint level

5. knurled screws

6. top plate

7. nozzle (diameter = 8 mm)

8. adjustable stand

9. target surface:-

a) flat surface θ = 900

b) curved surface θ = 1200

c) curved surface θ = 1800

THEORETICAL BACKGROUND:

Consider a jet of liquid striking a fixed curved vane ay the centre as shown in the figure below.

Þ The force produced by a jet striking the vane in the x-direction (horizontal) can be derived from the momentum equation:

Fx = m (v1x – v2x)

Fx : force exerted by the jet on the vane in x-direction

M : mass flow rate of the jet

= ρA jet v jet = ρQ

Q : volume flow rate

v1x : velocity of the coming jet in x-direction

= v jet

v2x velocity of the jet leaving the vane in x-direction

= v jet cos θ

Þ Fx = ρQ ( v jetv jet cos θ )

Þ Fx = ρ_Q2__ ( 1 – cos θ )

A jet

PROCEDURES:

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PART A: Flat surface with θ = 90°

  1. The water valve is closed and the pump is off.
  2. The top plate was removed. The diameter of nozzle was measured and recorded.
  3. The screw of the flat target was placed on the rod attached to the weight pan.
  4. The back top plate is placed and the knurled screws are tighted.
  5. Level the apparatus by adjusting the stand.
  6. The level gauge has been adjusted to point at the white line on the side of the weight pan then tighted. This is considering as balance position.
  7. Some mass is placed on the weight pan. The mass was recorded and the balance position is offset.
  8. The pump was switch on.
  9. The flow rate was increase by opening slowly the water valve until the level gauge points at the white line on the side of the weight pan. The balance position is achieved.
  10. The flow rate was measured and recorded.
  11. The steps 9 and 10 was repeated with adding more mass. 5 different values of mass are taken.
  12. The valve was closed and the pump is turn off.

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PART B: Curved surface with θ = 120°

  1. Step 1 to 12 is repeated by replacing the target with 120° curved surface.

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PART C: Curved surface with θ = 180°

  1. Step 1 to 12 is repeated by replacing the target with 180° curved surface.

SAMPLE CALCULATION:

  • For 90°:

Load = 100g 5 litres = 0.005 m3

Weight = _100_ x 9.81 time = 24:50 s

1000

= 0.981 N Q = _0.005_

24:50

= 0.204 x 10-3 m3/s

F theo = F = ρ _Q2__ (1 – cos θ)

A jet

F = (1000) [(0.204 x 10-3)2 ] (1 – 0)

0.05 x 10-3

= 0.832 N

  • For 120°:

Load = 100g 5 litres = 0.005 m3

Weight = _100_ x 9.81 time = 30:38 s

1000

= 0.981 N Q = _0.005_

30:38

= 0.165 x 10-3 m3/s

F theo = F = ρ _Q2__ (1 – cos θ)

A jet

F = (1000) [(0.165 x 10-3)2 ] (1 + 0.5)

0.05 x 10-3

= 0.817 N

  • For 180°:

Load = 100g 5 litres = 0.005 m3

Weight = _100_ x 9.81 time = 31:12 s

1000

= 0.981 N Q = _0.005_

31:12

= 0.161 x 10-3 m3/s

F theo = F = ρ _Q2__ (1 – cos θ)

A jet

F = (1000) [(0.161 x 10-3)2 ] (1 + 1)

0.05 x 10-3

= 1.037 N

DISCUSSION:

CONCLUSION:

REFERRENCES:


DATA AND CALCULATION:

Impact of jet

Jet (nozzle) diameter , d = 8 mm = 8 x 10-3 m

Jet area , A jet = 0.05 x 10-3 m2

Gravitational acceleration , g = 9.81 m/s2

Mass density of water , ρ = 1000 kg/m3

Measurement

No.

Deflection angle

Load

Jet flow rate measurement

Force of the jet

θ

Mass, m

Weight,

W

Vol. measured

Time observed

Q

Experimental

Theoretical

(°)

(g)

(N)

(litres)

(s)

(litres/s)

(m3/s)

x103

F exp = W (N)

F theo (N)

1

90°

100

0.981

5

24:50

0.204

0.204

0.981

0.832

2

200

1.962

5

16:07

0.311

0.311

1.962

1.934

3

300

2.943

5

14:15

0.353

0.353

2.943

2.492

4

400

3.924

5

11:29

0.443

0.443

3.924

3.925

5

500

4.905

5

10:44

0.479

0.479

4.905

4.589

Measurement

No.

Deflection angle

Load

Jet flow rate measurement

Force of the jet

θ

Mass, m

Weight,

W

Vol. measured

Time observed

Q

Experimental

Theoretical

(°)

(g)

(N)

(litres)

(s)

(litres/s)

(m3/s)

x103

F exp = W (N)

F theo (N)

1

120°

100

0.981

5

30:38

0.165

0.165

0.981

0.817

2

200

1.962

5

21:16

0.236

0.236

1.962

1.671

3

300

2.943

5

16:25

0.308

0.308

2.943

2.846

4

400

3.924

5

14:66

0.341

0.341

3.924

3.488

5

500

4.905

5

12:91

0.387

0.387

4.905

4.493

Measurement

No.

Deflection angle

Load

Jet flow rate measurement

Force of the jet

θ

Mass, m

Weight,

W

Vol. measured

Time observed

Q

Experimental

Theoretical

(°)

(g)

(N)

(litres)

(s)

(litres/s)

(m3/s)

x103

F exp = W (N)

F theo (N)

1

180°

100

0.981

5

31:12

0.161

0.161

0.981

1.037

2

200

1.962

5

21:97

0.228

0.228

1.962

2.080

3

300

2.943

5

18:22

0.274

0.274

2.943

3.003

4

400

3.924

5

15:78

0.317

0.317

3.924

4.020

5

500

4.905

5

13:63

0.367

0.367

4.905

5.388