DYNAMIC FORCE EXERTED BY FLUID JET ON STATIONARY AND MOVING PLATES

Dynamic forces exerted by fluid on plate normal to jet

Dynamic force exerted by fluid on stationery inclined plate

Force exerted by jet on stationery curved plate

Force exerted on moving plate held normal to plate

Let a fluid of density ρ moving with velocity V be striking a
plate moving in the same direction with the velocity of u.

So, relative velocity of jet = V-u

And mass of fluid striking jet per second = ρa(V-u)

Force exerted by jet = mass of fluid striking per sec * change
in velocity
= ρa(V-u)*(V-u – 0)
=ρa(V-u)2

Force exerted on moving plate held inclined in the direction normal to the plate

The angle between the jet and plate is θ as shown in the
figure.

Relative velocity with which jet strikes the plate is (V-u)

Mass of fluid striking plate per second is ρa(V-u)
Force exerted in the direction normal to the plate is          ρa(V-u)[(V-u)sinθ-0]

Fn = ρa(V-u) 2sinθ

Component of this force in the direction of jet = Fn sinθ
= ρa(V-u) 2sin2θ

Force exerted on curved plate moving along 

direction of jet

Let, V be the absolute velocity of the jet, a be the area of jet
and u be the velocity of the vane in the direction of jet.

So, relative velocity of the jet is (V-u) and after striking the
component of this velocity in the direction of jet is -(V-u)cosθ
(opposite in direction) as shown in figure.

Mass of fluid striking the plate per second = ρa(V-u)

Force exerted by the jet in the direction of jet = ρa(V-u)[(V-u)-{-(V-u) cosθ}]

    = ρa(V-u)2(1+ cosθ)