[lxwd]

Hi all,

I am now running a tutorial case dambreak using the interfoam solver. The meaning of pd really confuses me as I firstly expect it to be dynamic pressure (1/2*rho*U^2) until I got negative values of pd.

Could someone please explain to me what the physical meaning of pd is in dambreak case?

Also, when I checked the file interfoam.C under the interfoam solver directory, I found this equation "p=pd+rho*gh". Here, is p the total pressure, if pd is the dynamic pressure, or the static pressure?

Any help is greatly appreciated.

Best,
Lee

[lxwd]

No one knows the meaning of p and pd ?

Any suggestion is welcome!

[Houthuys]

Hi Lee,

Did you find answer to this question?

In OpenFOAM p_rgh=p-rho*gh is coined as dynamic pressure which seems to be the same as pd in foam-extended. So, I am curious to know does it really mean 0.5*rho*U^2?

If yes, this will bring many questions:

1- p=dynamic pressure (p_rgh) + hydrostatic pressure(rho*gh). So where is the static pressure?
2- if p_rgh=0.5*rho*U^2 why we need to consider it as additional unknown? why not writing it as function of velocity?

I believe p_rgh is the static pressure (or static + dynamic at stagnation point) but I'm not sure.

any help is appreciated.

Edit:
I've found the answer (I hope this time is the correct one)
p_rgh or pd is simply the static pressure (p) - hydrostatic pressure (rho*gh). It has nothing to do with dynamic pressure (0.5*rho*U^2)
If you want the static pressure use: p=pd+rho*gh
if you are interested in the dynamic pressure reconstruct it from the velocity field

For more information: rasInterFoam appears to give erroneous results for “pd”.