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taw September 15, 2008 00:05

2nd order conservative schemes
 
Dear fellows,

I want to use second order conservative schemes, especially for the k.e. therm that would keep the code stable or realizable enough, for DNS stability simulation of a high Re flow. The main reason to go for 2nd order is to keep my present 2nd order code intact, i.e. instead of going to the 4th order scheme.

Being new to these idea and after skimming through Morinishi, 1998 I kind of got the impression that for 2nd order schemes to be conservative in the kinetic energy sense, one should use a uniform grid. Do you think I got the idea right.

Or is there another way around to tackle this problem, without going for the 4th order scheme.

My code use a collocated grid in primitive variable formulation in Cartesian coordinate system only. I plan to simulate a simple geometry, a flat plate.

Regards

TAW

Andrew Clarke September 16, 2008 07:05

Re: 2nd order conservative schemes
 
I had a similar problem in my work before. I just reduced the underrelexation factors in the Solution Controls panel for appropriate factors.

In my case, i got pressure-correction divergence reported in second order solving but when i reduced the pressure underrelaxation to 0.2 and momentum to 0.4, i could get stability quite well but solutions took more iterations. The selection of underrelaxation factors is a matter of trial and error.


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