|September 26, 2014, 03:46||
question on the physical meaning of p_rgh
Join Date: Mar 2009
Posts: 116Rep Power: 9
Hello, I have found that p_rgh is often used in OpenFOAM.
According to Henrik thesis (4.21)
"the modified pressure p_rgh is obtained by removing the hydrostatic pressure from the pressure."
I think rho*g*h is not the static pressure, as rho is not a constant, thus it should be int(rho*g)dz. So the question is what's the physical meaning of p_rgh.
|September 26, 2014, 04:55||
Join Date: Jan 2011
Posts: 340Rep Power: 8
p_rgh does not have any physical meaning, it is just a convenient numerical technique.
The expression is not with h, but with z:
p_rgh = p - rho*g*z
This means that if a cell is at z = 0, p_rgh = p.
Also, as you pointed out, if a cell is in water at one instant p_rgh = p - rhoWater*g*z, and if at the next time step it is in air: p_rgh = p - rhoAir*g*z, it may be induce quite a huge variation in p_rgh.
In short, p_rgh is not hydrostatic pressure because it takes into account what happens at a point, and not at all the points above. I hope this clarifies things a little.
|Thread||Thread Starter||Forum||Replies||Last Post|
|Physical meaning of TKE||jibreel||Main CFD Forum||2||January 6, 2014 05:31|
|Partition does not start on physical sector boundary!!??||immortality||Lounge||1||December 8, 2013 16:04|
|viscosity ratio in wake of ellipse - physical meaning?||MachZero||Main CFD Forum||8||July 22, 2013 16:32|
|Some question about channeloodles and average value||spwater||OpenFOAM||0||August 21, 2009 15:28|
|Dual-time stepping question||lost.identity||Main CFD Forum||0||June 4, 2009 03:43|