AnsweredAssumed Answered

Sonic Flow Pipe Exit

Question asked by Dave Frenk on Jul 23, 2011
Latest reply on Jul 25, 2011 by Rich Bayless

Perhaps someone has an answer to this problem I have. After running multiple flow simulations on a piping discharge from a relief valve the results show the gas velocity greater than mach 1, which cannot happen. See link below.



Here are the conditions I'm using:



-pipe size 3", discharge from 3" pipe after an elbow

-inlet pressure (initial condition): 1670 psi

-inlet temp (initial condition): 135F

-outlet static pressure (boundary condition): 14.7 psi


The resulting mach number at the exit is 4.3, using the high mach flow option.


I'm not sure if I have the boundary conditions setup incorrectly or what else I can change.


Goal NameUnitValueAveraged ValueMinimum ValueMaximum Value
Static pressure inlet [lbf/in^2]1498.371497.491496.981498.37
Static pressure outlet [lbf/in^2]14.7014.7014.7014.70
Mass flow [lb/s]-28.63-28.64-28.65-28.63
Velocity outlet [ft/s]1791.141789.881788.921791.14
Velocity inlet [ft/s]637.21637.70637.21638.05
Mach number outlet [ ]4.344.344.344.34


I appreciate any feedback. I can send the solid models if anyone is interested.