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-   -   Starting 3D simulation with ideal gas f.p.error (http://www.cfd-online.com/Forums/fluent/37490-starting-3d-simulation-ideal-gas-f-p-error.html)

Ralf Schmidt August 5, 2005 06:59

Starting 3D simulation with ideal gas f.p.error
 
Hi,

I am running a simulation of a 3D geometry with air at constant density and it works very fine.

Now I changed the air properties to ideal gas (there are up to 3 bars pressure on my device). When I start iterating, the floating point error occurs. Even when I set courant number to 0.1 and at the mass flow inlet boundary ant pressure outlet boundary all turbulence values to 0.1 (k-epsilon) the floating point error occurs before the first iteration is finished.

What is wrong? Any help is highly appreciated!

Ralf

Swarup August 5, 2005 09:39

Re: Starting 3D simulation with ideal gas f.p.er
 
I am not sure but it may be due to bad input/initialization. Since you said that error occurs before the first iteration is over, it indicates to some problem with your input data.

Swarup.

Ralf Schmidt August 5, 2005 09:58

Re: Starting 3D simulation with ideal gas f.p.er
 
thanks for your answer! My input (inlet into the geometrie) is just a constant mass flow rate normal to boundary. That works fine for the constant density simulation. Or what kind of input do you maen?

Ralf

Swarup August 5, 2005 10:46

Re: Starting 3D simulation with ideal gas ? f.p.er
 
I mean inputs other than boundary data like those in initialization, property data, etc.

alex August 5, 2005 15:57

3D simulation with ideal gas
 
Hi

I had a similar problem with the initialization but when I initialized my model, appeared both, a pressure limited and viscosity limited on all cells before I began the iteration process. What can I do?

Alex

Swarup August 5, 2005 22:52

Re: 3D simulation with ideal gas
 
answer to this problem can be found in the User-Guide. if you see the message viscosity limited to ----- in ---cells and pressure limited to--- in ---- cells, then it has something to do with your problem set-up. your variables of interest reach the maximum/minimum limit set to prevent solver from crashing. FLUENT user guide tell that you should review your problem set-up with respect to type and quality of grid, appropriate boundary conditions, etc.

Swarup.


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