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-   -   Negative densities at more than 100 cells (http://www.cfd-online.com/Forums/cd-adapco/56830-negative-densities-more-than-100-cells.html)

Luke October 11, 2008 03:59

Negative densities at more than 100 cells
 
Hey everyone, I'm pretty new to Star-CD and am having some problems with a model that I have been trying to get running for quite a while now.

Basically what I am trying to do it to inject some fuel into a constant volume chamber. This is the starting point and then I will introduce a porous medium but this basic setup isn't working. I have run some models using es-ice in which I have sprayed fuel into the moving cylinder and they worked fine but now I am just trying to simulate fuel spray at one set crank angle (i.e. just a fixed volume) but I get an error that says: "Error 076: Negative densities at more than 100 cells" after only a few iterations. The fuels starts injecting before the error and everything seems to be as expected at these iterations.

If anyone know what the problem might be, I would really appreciate it.

Thanks


cachinarcrc October 14, 2008 21:12

Re: Negative densities at more than 100 cells
 
I have got the same error"Error 076: Negative densities at more than 100 cells" when I simulate the diesel engine,and the soft Engineers sometimes have not idea to deal with it except for asking for "reduce the time step,or uder-relaxation factor,etc".But this is no useful.

usker October 15, 2008 10:14

Re: Negative densities at more than 100 cells
 
try to locate your injector a little deeper into the domain (not on the surface of the domain)

Luke October 15, 2008 18:00

Re: Negative densities at more than 100 cells
 
Hi,

Thanks for the tip. I have located the injector 1.5mm radially the edge and 1.3mm in the z-direction. The other thing is that it gets the negative densities much before the fuel injection starts. Any other ideas?

allan October 27, 2008 16:52

Re: Negative densities at more than 100 cells
 
You can try checking your reference pressure or relax very heavily on temperature and density or if you have a pressure outlet make sure that the pressure on it is realistic.

allam

Emir December 2, 2008 05:14

Re: Negative densities at more than 100 cells
 
you should change your time step and then your problem will be solved


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