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Paul April 7, 2008 13:19

RSM with Eulerian, tips for convergence?
I'm running a RSM unsteady simulation with Eulerian multiphase enabled with two phases (a gas and a particle stream). I'm having trouble getting it to converge however. I'll get a few seconds into the simulation and then I start getting errors followed by the inevitable "floating point exception".

Anyone have any tips on how to get it to converge?

fluent April 9, 2008 07:19

Re: RSM with Eulerian, tips for convergence?

Paul April 9, 2008 13:01

Re: RSM with Eulerian, tips for convergence?
The RSM isn't the problem. I can solve the model using only RSM, its when the Eulerian is enabled that I'm getting problems.

Paul April 9, 2008 13:25

Re: RSM with Eulerian, tips for convergence?
Okay let me explain in a little more detail what I've done:

I am attempting to run a simulation of a cyclone using the RSM-unsteady-eulerian multiphase model.

Previously the model has converged using RSM-Unsteady with no multiphase model.

I ran with the multiphase enabled (2 phases), and I kept getting floating point errors once I got to a certain point (around 4s). I checked fluent's manual and they suggested running the simulation without volume fraction selected in the solution menu until convergence.

I ran this model until the solution conditions were basically steady state (no changes in results for varying time steps). I then reenabled the volume fractions, but it soon bombed out due to the "turbulent excursions".

I then tried turing the turbulence equations off in the solution, and have been running it since. I'm around 48s, and based on the results I have it is nowhere near convergence. I'm running with a time step size of .001s which converges in about four iterations, however when I try to increase the size the residuals diverge wildly.

Anyone have any suggestions about what I can do (preferably with all the solution equations (turbulence/volume fraction) enabled)?

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