Impulse-Momentum Equation PDF

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Impulse- Momentum Equation The Impulse-Momentum Equation for fluid can be derived from Newton’s second law of motion,

Application of Impulse-Momentum Equation (a) To determine the resultant force acting on the boundary of a flow passage by a stream of fluid as the stream changes its direction or magnitude of both. Problem of this type are, pipe bends, reducers, stationary and moving vanes, jet propulsion etc. (b) To determine the characteristics of flow when there is an abrupt change of flow section. Problems of this type are: sudden enlargement, in pipe, hydraulic jump in a channel etc. Thrust on a reducing pipe bend: P2 Rx, Ry and R

W P1

p1 A1 cos 1  p2 A2 cos  2  Rx  Q V2 cos  2  V 1 cos 1 

Example 1: Water is following through a 600 reducer bend and discharges into the atmosphere as shown in the figure below. The inlet diameter is 210 mm and the outlet diameter is 160 mm. If the flow rate of water is 0.35 m3/s, find the force exerted by water on the bend.

Example 2: Water is following at the rate of 0.25 m3/s through a reducer bend as shown below. The inlet diameter is 300 mm and the outlet diameter is 150 mm. The center of the outlet section is 1.5 m below the inlet section. If the inlet pressure is 150 kpa, find the force exerted by the water.

Assignment Water enters a horizontal reducing pipe with a velocity of 5 m/sec and a pressure of 78.480 kN/m2. If the diameters at the entrance and exit sections are 30 cm and 20 cm respectively, calculate force exerted by the water that acts on the bend of the pipe. RY R RX

V1 60 0

V2...