Dear all,

Shld the outlet static pressure for a duct flow be zero?

Only if you are flowing into a vacuum, or you have chosen a non-dimensionalization that results in zero non-dimensional pressure at that value of exit pressure.

Hi,

I have a similar question about the pressure BC. For an incompressible flow, can I arbitrarily set a static pressure value for the pressure outlet? Does the value I set affect the modelling result?

Regards,

Barry

What is ur inlet condition? If it is vel. inlet then value of static pr. for incomp. flow will not have any effect on the flow(except for pr. values)

or you have chosen a non-dimensionalization that results in zero non-dimensional pressure at that value of exit pressure.

You mean taking the taking the absolute pressure as 0? as in just measuring the gauge pressure? or am i understanding this wrong

If you are computing gage pressure then zero may be a valid value. Then your nondimensionalization would look something like

p_non = (p - p_baseline)/p_ref

where p_ref is the pressure used to non-dimensionalize the pressure variables and p_baseline is whatever baseline pressure you are computing gage pressure relative to. But absolute static pressure should not be zero, unless as noted above you are expanding into a perfect vacuum.

Could you please explain why the value of static pr. for incomp. flow will not have any effect on the flow if using velocity inlet BC?

Thanks,

Barry

Is simple... for incomp. flows pr. enters the equation as only delta P ... so whatever be the absolute value the diffenence will remain the same and flow velocity will decide the pressure gradient... plz go through the analytical soultion of a pipe flow for a laminar case.