outlet static pressure of a duct flow
 

Dear all,

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

Re: outlet static pressure of a duct flow
 

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.

Re: outlet static pressure of a duct flow
 

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

Re: outlet static pressure of a duct flow
 

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)

Re: outlet static pressure of a duct flow
 

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

Re: outlet static pressure of a duct flow
 

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.

Re: outlet static pressure of a duct flow
 

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

Re: outlet static pressure of a duct flow
 

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.