A fire monitor nozzle is bolted by its flange to the top of a rigid vertical…

PHYSICS · Multi-part · Fermi University Physics · Fluids & Continuum Physics · Kinematics, conservation laws and ideal flow · Kinematics, conservation laws and ideal flow

Fluids and Continuum Physics, Ch Conservation of mass, momentum and energy

Problem

A fire monitor nozzle is bolted by its flange to the top of a rigid vertical standpipe and points horizontally. Its inlet bore has diameter

100\ \mathrm{mm}

and its circular exit has diameter

40\ \mathrm{mm}

. Water of density

1000\ \mathrm{kg\,m^{-3}}

passes steadily through it at

Q = 0.030\ \mathrm{m^3\,s^{-1}}

, and the jet discharges into the atmosphere. The gauge pressure at the inlet flange is given as

3.0\ \mathrm{bar} = 3.0\times10^{5}\ \mathrm{Pa}

(this chapter has no way to compute it). Treat the flow as incompressible with uniform speed across the inlet and the exit; work in gauge pressure throughout, so the atmosphere outside the nozzle contributes nothing; neglect the weight of the nozzle and of the water in it, which acts vertically. ((a)) Find the speed of the jet at the exit. ((b)) Taking a control volume that cuts the water and the nozzle wall at the flange, find the magnitude of the horizontal force the flange bolts must supply.

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