IMPACT OF JET

 

IMPACT OF JET

Momentum Equation: - F= m (dv/dt)

Impulse momentum Principle: - F.dt = m.dv

Angular momentum equation: - 

• IMPACT OF JET:

1.   Force exerted by a jet of water strikes normally on a fixed vertical blade: -

Fig.1 | Impact of jet on vertical fixed plate

Reaction force in 'X' direction -

= ρAV₀ [V₁ - 0] 

[∵ There is no component of V₂ in the ‘X’direction]

= ρA(V₀)² [∵ V₁ = V₀]

Reaction force in Y direction-

F_y’ = 0

2.   Force exerted by a jet of water strikes normally on a fixed blade inclined at an angle θ: -

Fig.2 |  Impact of jet on inclined fixed plate

Reaction force 

 = ρ AV²sinθ

F_x = F_ncos(90-θ)

=F_nsinθ

= ρAV²Sin²θ   

F_y = F_nsin(90-θ)

=F_ncosθ

= ρAV²Sinθ cosθ

 

3.   Force exerted by a jet of water strikes on a fixed curved plate: -

a.   Jet strikes at the center –

Force exerted in the direction of jet

= ρAV [V + Vcosθ)]

= ρAV² [1+ cosθ]

 

Force exerted in the perpendicular direction of jet

= ρAV [0 - Vsinθ]

= ρAV² sinθ

 

b.   Jet strikes the blade (symmetrical) tangentially –

 

Force exerted in the direction of jet

= ρAV [V cosθ + Vcosθ)]

= 2 ρAV² cosθ

 

Force exerted in the perpendicular direction of jet

= 0

 

[NOTE: If plate is asymmetrical, then inlet angle will differ from outlet angle.

Then, F_x = ρ AV² (cosθ + cosα)

And F_y = ρ AV² (V sinθ – Vsinα)]