Lubricating oil, with a relative density of 0.79, flows around a 90¨¬ bend. The pipe diameter is 0.45m, and the oil has a pressure head of 7m and the flow is 1.7m3/s. Find the force exerted by the oil on the bend.
Oil density = 0.79 X 103
Volumetric mass flow rate = 1.7 m3/s
Pipe diameter = 0.45 m
Pressure head (¥÷) = 7m
1 answer

Use the momentum change law.
The force exerted on the fluid equals the rate of change of the fluid's momentum, which is a vector. For a 90 degree turn, the momentum change vector bisects the angle betweeb the pipes and equals sqrt2 times the momentum flow rate.