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Old   July 12, 2007, 11:58
Default Supersonic Combustion Fluent
alexandre neophytou
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Hello, I am modelling Supersonic Combstionn with Fluent.

I started with a 2d case Coupled Implicit solver, and every thing was pretty fine. The CFL number had to remain under 1 though ( slow convergence, anyway).

Now I try to do the same with a 3d calculation, a,non-reactant flownd it is VERY Slow. I am currently computing a mixing case. What should I do. Is it a problem linked to Couple or Implicit solver? I have like 420 000 nodes for a fine grid and 120 000 nodes for a coarse grid. I use k-epsilon. I refined the coarse grid with gradient adaptation and with the refine grid there is this message at each iteration: " reversed flow in 44 faces on pressure outlet 3 turbulent viscosity limited to viscosity ratio od 1.00000+5 in 2cells"

That did not appear without refinement and it does not appear for the fine grid. Does it slow down the calculations?

Many thanks,

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Old   July 12, 2007, 12:11
Default Re: Supersonic Combustion Fluent *NM*
alexandre neophytou
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Old   July 26, 2007, 16:49
Default Supersonic Combustion Fluent
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Fluent recommends SA model for high speed flows ... I have run with that .... if u are interested in turbulent kinetic energy/dissipation rate ... u can converge with SA and then switch to Kepsilon... it is possible to get unrealistic results about turblence production and viscosity ratios ... look only for the quantites u require and match with expts ...

I have faced same problem with turbulence predictions

reverse flow should vanish as the iterations progress

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