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Old   October 26, 2009, 09:31
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Dear CFD friends,

now,I have a question about calculation of compressible flow at low mach,But I can not get a good result.I can not find reasons. Calculation condition as follows:
[1]stream flow Mach number M=0.01
[3]space: MUSCL method
Roe average method
[4]time: LUSGS method
[5]Laminar flow method(Compressible flow Code is used)

By these conditions,for example,If Roe-average method is used at very low Mach number(Mach number M=0.01) by Compressible flow Code,Can I get good result?
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Old   October 26, 2009, 11:19
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You will get very bad results at such low mach numbers with a compressible code. You need to use some preconditioner. A easy preconditioner for roe scheme can be found in

Herve and Viozat
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Old   October 26, 2009, 22:21
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Hi, im mechanical engineering student and i make an unsteady compressible navier-stokes simulation at low speed, using C++, mccormack scheme.

when i place an obstacle, i got good result, with 1500 iteration i can see that the flow is convergence and it has vortex flow on it. Beautiful ...

The problem is interaction between fluid flow and boundary is very weak, what should i do to fix it??? It is channel flow with u = 3 m/s, channel length 10 cm, height 10 cm.

can somebody help me???
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