Help, nagative densities found?
 

Hi:

I am trying modelling a 2 phase flow in an engine. The gasous h2 and liquid o2 are injected into the chamber.

Each parcel represented about 8.413e+7 droplets whose diameter is 4 memimeter. I found if the number of the parcels is less than 30, everything is ok. Nut when i increased the number of the parcels to 120, negative densities will come out ? why ? Help me please.

Any suggestions is highly appreciated.

Thanks.

I am using star_cd v3050A.

Re: Help, nagative densities found?
 

Hi Rosary

I've had same problem when I calculated gasturbine combustor. So I think this can help U.

Take follow these steps.

1. solve the problem with const. density 'till it converges little. (Don't have to be fully converged)

2. Restart from previous solution as an initial condition with ideal gas law.

This steps will decreas chance to meet that NEGATIVE DENSITY.

Decreas of relaxation factor of T can help U also.

I hope this helps U.

-Roh