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INPUT   DATA

♥ EXAMPLE Of Input/Output

Title

Flow rate, Q		gal/min
Fluid specific gravity, γ
Inlet Pressure, P1		psi
Pipe inlet diameter, D1		in
Pipe outlet diameter, D2		in
Bend Angle, θ		°

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OUTPUT   VARIABLES   &   GRAPHS

VARIABLES	Values	Units
♦♦ Force magnitude, F		lb
♦♦Force direction, α		°
♦ X-component of force, Fx		lb
♦ Y-component of force, Fy		lb
♦ Outlet Pressure, P2		psi
♦ Inlet Velocity, V1		ft/s
♦ Outlet Velocity, V2		ft/s

Forces Due To Pipe Bend And/Or Diameter Changes

When a flowing fluid changes direction, a force will act in the bend. Thrust blocks are used in pipe bends to withstand the forces on the pipe caused by momentum change and unbalanced pressure of the fluid flowing in the pipe. Consider a pipe bend lying in the horizontal plane with or without a diameter change. The resultant force and its direction can be estimated by the equations:

where
     F = reacting force on bend
     α = direction of reacting force with respect to x-axis, anticlockwise +ve
     F_x = x-component of force
     F_y = y-component of force
     Q = average flow rate
     θ = angle of pipe bend, -180 to 180, anticlockwise +ve w.r.t. x-axis
     D₁ = internal pipe internal diameter before bend or size change
     D₂ = internal pipe internal diameter after before bend or size change
     P₁ = pressure before bend or size change
     P₂ = pressure after bend or size change
     A₁ = area before
     A₂ = area after
     V₁ = flow velocity before
     V₂ = flow velocity after
     γ = fluid specific gravity; water = 1
     ρ = fluid density

Tips

    ◊ Use link EXAMPLE Of Input/Output  to demo data entry expectations and results; you may edit & use it as starting point

BIBLIOGRAPHY

• Munson BR, Young DF & Okhiishi TH; Fundamentals of Fluid Mechanics, John Wiley & Sons, Inc., NJ, 2005.
• Hicks TG; Mechanical Engineering Formulas, Pocket Guide; McGraw Hill, New York, 2003, Chapter 10.