# Retrieving Unsteady pressures rans equations

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 December 14, 2021, 11:26 Retrieving Unsteady pressures rans equations #1 New Member   suresh Join Date: Dec 2021 Posts: 11 Rep Power: 2 Hi, I am solving rans equations. I am able to get the pressures due to convective acceleration (u.d(u, n))., which leads to 0.5 *rho* u^2 upon spacial integration. May I know how to get the unsteady pressure caused due to temporal acceleration. d(u, t) ?? Can some one help or share view?

December 14, 2021, 11:35
#2
Senior Member

Filippo Maria Denaro
Join Date: Jul 2010
Posts: 6,191
Rep Power: 66
Quote:
 Originally Posted by dskvsp Hi, I am solving rans equations. I am able to get the pressures due to convective acceleration (u.d(u, n))., which leads to 0.5 *rho* u^2 upon spacial integration. May I know how to get the unsteady pressure caused due to temporal acceleration. d(u, t) ?? Can some one help or share view?

1) if your solving the steady RANS equations there is no acceleration
2) if you are solving the URANS equations for compressible flows you have all that take into account the time-dependent pressure field.
3) if you are solving the unsteady URANS equations for incompressible flows you have to solve the Poisson equation for the pressure. But be aware that this is not the thermodynamic pressure.

December 14, 2021, 11:44
#3
New Member

suresh
Join Date: Dec 2021
Posts: 11
Rep Power: 2
Quote:
 Originally Posted by FMDenaro 1) if your solving the steady RANS equations there is no acceleration 2) if you are solving the URANS equations for compressible flows you have all that take into account the time-dependent pressure field. 3) if you are solving the unsteady URANS equations for incompressible flows you have to solve the Poisson equation for the pressure. But be aware that this is not the thermodynamic pressure.
Thanks Denaro, I will look into the urans equations and get back if I need help.

 Tags bernouli, dynamic pressure, fluent, rans, unsteady pressure