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 Nelson August 1, 2002 07:10

Turn off velocity Equations

Dear all,

I want to seek a suggestion to turn off the velocity equations, i.e. fixed U, V, W, for the Solver run. Anyone can help me? Thank you.

Nelson

 cfd guy August 1, 2002 10:06

Re: Turn off velocity Equations

Which solver are you using?
In CFX-5 you can set fluids = f in the expert parameters.
In TASCflow, in the PRM file: fluids = f; turbmd = f; tmptre = f will turn of the fluids, turbulence and energy equations respectively.
In CFX-4, I don't know how to do it.
Regards, cfd guy

 Sergei August 2, 2002 03:48

Re: Turn off velocity Equations

Hi, excuse my ignorance please.I would like to know when & why it is suitable to turn off these eqs?

 Astrid August 2, 2002 05:08

Re: Turn off velocity Equations

I can be helpfull if you want to calculate different temperatures or (passive) scalars distributions at a given flow field. Provided they do not disturb your flow field, that's what you assume..

Astrid

 Astrid August 2, 2002 05:11

Re: Turn off velocity Equations

In CFX 4 you can turn off UVW and p with the keyword:

ITERATIONS OF HYDRODYNAMIC EQUATIONS 0

in the subject: >>SOLVER DATA >>PROGRAM CONTROL

Astrid

 Sergei August 2, 2002 06:07

Thank you ,Astrid

 cfd guy August 2, 2002 08:48

Re: Turn off velocity Equations

I use to turn off all equations (turbulence, fluids and energy) when I'm testing a new moving grid with the TASCFlow code.

 Jan Rusås August 2, 2002 18:09

Re: Turn off velocity Equations

I very often use this approach when dealing with combustion or heat transfer problems. I have noticed in such problems that the velocity and pressure field might have converged or does not change anymore but the residuals for the temperature/enthalpy is still decreasing. It can take very long time, many iterations, for settling the solution for the temperaure, solving the velocity and pressure just increase the computational time. So I normally get a converged solution on the velocities and then do a restart without solving the velocities. I have found this to be very efficient.

 Drona September 20, 2002 06:16

Re: Turn off velocity Equations

When you put fluids = f in tascflow, the momentum as well as continuity equations are turned off. Is it possible to just turn of momentum or continuity equation selectively, or even better, u-, v-, or w- componets of momentum equations separately? I normally get mass converged very quickly but one particular momentum equations (W in my case as the main flow direction is Z) takes time to solve.

Thanks

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