Experiment no 7 fluid mechanics lab
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This document describes an experiment to verify the momentum equation through measuring the impact of a water jet. The objective is to experimentally test Newton's second law of motion as it applies to fluid momentum. The apparatus required includes an impact of jet setup, weights, and a stopwatch. The theoretical basis is explained, noting that the sum of external forces equals the rate of change of momentum. The experimental setup and procedure are outlined, involving measuring the discharge and velocity of the jet using a collecting tank and nozzle, and determining the force on a target plate by adding weights to return it to its initial position. Observations are recorded for different flow rates.
![LAB NO#7
IMPACT OF JET
Objective:
To verify the momentum equation experimentally through impact of jet experiment.
Apparatus Required: Impact of jet apparatus, weights and stop watch.
Theory:
The momentum equation based on Newton’s 2nd law of motion states that the algebraic sum of
external forces applied to control volume of fluid in any direction equal to the rate of change of
momentum in that direction.
The external forces include the component of the weight of the fluid and of the forces exerted
externally upon the boundary surface of control volume.
If a vertical water jet moving with velocity ‘V’ made to strike a target (Vane) which is free, to
move in vertical direction, force will be exerted on the target by the impact of jet.
Applying momentum equation in z- direction, force exerted by the jet on the vane, Fz is given by
F = ρQ (Vzout- VZ in)
For flat plate, Vz out= 0
Fz = ρQ (0-v)
FZ = ρQv
For hemispherical curved plate, vz out= -v, vz in= v
Fz = ρQ [v+ (-v)]
FZ = 2 ρQv
Where Q= Discharge from the nozzle (Calculated by volumetric method)
V= Velocity of jet = (Q/A)
Experimental setup:
The set up primarily consists of a nozzle through which jet emerges vertically in such a way that
it may be conveniently observed through the transparent cylinder. It strikes the target plate or
disc positioned above it. An arrangement is made for the movement of the plate under the
action
of the jet and also because of the weight placed on the loading pan. A scale is provided to carry
the plate to its original position i.e. as before the jet strikes the plate. A collecting tank is utilized
to find the actual discharge and velocity through nozzle.
Procedure:
i. Note down the relevant dimensions as area of collecting tank and diameter of nozzle.
ii. When jet is not running, note down the position of upper disc or plate.
iii. Admit water supply to the nozzle.
iv. As the jet strikes the disc, the disc moves upward, now place the weights to bring
back
the upper disc to its original position.
v. At this position find out the discharge and note down the weights placed above the
disc.
vi. The procedure is repeated for different values of flow rate by reducing the water
supplyin steps.
Fig no.6.1](https://image.slidesharecdn.com/experimentno7-140603222229-phpapp01/85/Experiment-no-7-fluid-mechanics-lab-1-320.jpg)
Experiment no 7 fluid mechanics lab
- 1. LAB NO#7 IMPACT OF JET Objective: To verify the momentum equation experimentally through impact of jet experiment. Apparatus Required: Impact of jet apparatus, weights and stop watch. Theory: The momentum equation based on Newton’s 2nd law of motion states that the algebraic sum of external forces applied to control volume of fluid in any direction equal to the rate of change of momentum in that direction. The external forces include the component of the weight of the fluid and of the forces exerted externally upon the boundary surface of control volume. If a vertical water jet moving with velocity ‘V’ made to strike a target (Vane) which is free, to move in vertical direction, force will be exerted on the target by the impact of jet. Applying momentum equation in z- direction, force exerted by the jet on the vane, Fz is given by F = ρQ (Vzout- VZ in) For flat plate, Vz out= 0 Fz = ρQ (0-v) FZ = ρQv For hemispherical curved plate, vz out= -v, vz in= v Fz = ρQ [v+ (-v)] FZ = 2 ρQv Where Q= Discharge from the nozzle (Calculated by volumetric method) V= Velocity of jet = (Q/A) Experimental setup: The set up primarily consists of a nozzle through which jet emerges vertically in such a way that it may be conveniently observed through the transparent cylinder. It strikes the target plate or disc positioned above it. An arrangement is made for the movement of the plate under the action of the jet and also because of the weight placed on the loading pan. A scale is provided to carry the plate to its original position i.e. as before the jet strikes the plate. A collecting tank is utilized to find the actual discharge and velocity through nozzle. Procedure: i. Note down the relevant dimensions as area of collecting tank and diameter of nozzle. ii. When jet is not running, note down the position of upper disc or plate. iii. Admit water supply to the nozzle. iv. As the jet strikes the disc, the disc moves upward, now place the weights to bring back the upper disc to its original position. v. At this position find out the discharge and note down the weights placed above the disc. vi. The procedure is repeated for different values of flow rate by reducing the water supplyin steps. Fig no.6.1
- 2. Observation: Diameter of nozzle (d) = 10 mm Area of the nozzle (A) = πd2/4 Mass density of water = 1gm/cm3 Area of collecting tank = 1200cm2 When jet is not running, position of upper disc = ......................... cm SR NO Discharge/velocity measurment Weight (w) Time (t) Volume(v) Q F(threotical) F(practical) 1 500 g 52 sec 5 4.90 49 500 N 2 500 g 50 sec 5.5 4.90 53.9 500N 3 600 g 46.5 sec 6 5.88 70.56 600N Precaution: 1. Apparatus should be in leveled condition. 2. Reading must be taken in steady conditions. 3. Discharge must be varied very gradually from a higher to smaller value. Comments: The difference between the theoretical value and the actual value may mainly due to human and servicing factors such as parallax error. This error occur during observer captured the value of the water level. Besides that, error may occur during adjusting the level gauge to point at the white line on the side of the weight pan. Other than that, it also maybe because of the water valve.