Dynamic Fluid Forces

[GalileoG]

Hello all,

I'm a structural engineer with VERY little background (if any at all) in fluids. I'm trying to calculate the stresses caused by a fluid that is discharged from a pipe. I can't seem to find for the life of me my undergraduate fluid mechanics textbook. Can you refer me to any publications/guides that are available online that may be able to help me?

Much thanks!

Regards,

Clansman

 

[RWF7437]

http://www.engineeringtoolbox.com

Also, ANY Hydraulics text book or reference book will cover this topic.

good luck

 

[BigInch]

It can be approximated by Pressure x cross-sectional area of flow.

http://virtualpipeline.spaces.msn.com

 

[BRIS]

Do you mean 1) the impact of the fluid discharge by a pipe onto a wall or 2) the thrust exerted by the pipe on to its encasement.

1) Impact of a jet normal to a wall: Force = rate of change of momentum = Ro x Q x V

Ro density 1000 kg/m3
Q m3/sec
V m/sec
F = N


2) For an open end discharge thrust force into the encasement is negligible.

 

[stanier]

API 2000 is a good reference

Geoffrey D Stone FIMechE C.Eng;FIEAust CP Eng

http://www.waterhammer.bigblog.com.au

 

[BigInch]

http://www.sstusa.com/99janmar.htm#jan99

The escaping fluid creates a jet force which is transferred through the pipng system. This force must be resisted by the pipe supports if the pipe is incapable of resisting the force internally. The magnitude of the force is usually given by the valve manufacturer. It can be easily calculated however, for those situations where the valve vents to the atmosphere.

ANSI B31.1 recommends the following method for calculating this force.

F = DLF ( MV/32.2 + PA) (English units)
F = DLF ( MV+ PA/10^6) (SI units)

V = SQRT(50,113 (ho - a)/(2b - 1) ) (English units)
V = SQRT(2.0085 (ho - a)/(2b - 1) ) (SI units)

P = (M/A) (b - 1)/b SQRT(48.33 (ho - a)/(2b - 1)) - Pa (English units)
P = (M/A) (b - 1)/b SQRT((1.995 x 10^12) (ho - a)/(2b - 1)) - Pa (SI units)

where

F = Discharge force (lb., N)
DLF = Dynamic load factor (dimensionless), see discussion below
M = Mass flow rate from valve x 1.11 (lbm/s, kg/s)
V = Fluid exit velocity (ft/s, m/s)
P = Static gauge pressure at discharge (psi, N/m^2)
A = Discharge flow area (in^2, mm^2)
Pa = Atmospheric pressure (psi, N/m^2)
ho = Stagnation enthalpy of pipe fluid (Btu/lbm, J/kg)
a, b are as given below:


a b (dimensionless)
Steam Condition Btu/lbm J/kg
Wet, <90% quality 291 675,411 11
Saturated, > 90% quality 823 1,910,183 4.33
Superheated 831 1,928,751 4.33

http://virtualpipeline.spaces.msn.com

 

[BRIS]

http://www.cartage.org.lb/en/themes...FluidMechanics/Dynamics/Momentum/Momentum.htm