# Impact of Jet

CVEN-3313 Theoretical Fluid Mechanics

MODULE#4 : Application of Impact on a Jet

1. OBJECTIVE

To use the momentum equation to estimate the force exerted by a jet on a stationary target.

2. THEORY

The momentum equation in the vertical (z) direction can be written as:

Applying the momentum equation for a control volume including the forces acting on a flat target or hemispherical target gives: (1a : flat)

(1b : hemi)

It is assumed that the velocity going out of the control volume is equal to the velocity coming in. Additionally, the elevation difference within the control is assumed to be negligible. The vertical force caused by the jet is balanced by the mass placed on the weight pan.

(2)

The initial velocity of the jet, v0, is :

(3)

From Bernoulli’s equation, the jet velocity, v, in the control volume at the target is :

(4)

Combining equations (1) through (4), the following equations can be obtained for the flat and hemispherical targets, respectively.

(5a : flat) (5b : hemi)

3. PROCEDURE

1) Install the flat target in the jet apparatus.

2) Level the apparatus and adjust the pointer for zero deflection. 3) Place a 50g mass on the weight pan.

4) Increase the flow rate until the weight induced by the 50g is balanced by the force of the jet. 5) Measure the actual flow rate, Qactual, by recording the time required to collect 10L. Use the volume gauge on the bench. 6) Repeat steps 3-5 for 100, 200, 300, 400 and 500g mass increments. 7) Repeat the procedure for the hemispherical target.

4. RESULTS & ANALYSIS

1) Equations (5a) and (5b) are non-linear with respect to flow rate Qtheor. These can be solved...

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