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Vajra December 10, 2001 16:47

Should I use preconditioning ?
Hello all,

Can anyone tell me if I can use a compressible flow solver using Roe scheme to simulate a low speed flow of Mach number around 0.01 or lower without preconditioning ?



Alexey December 12, 2001 06:23

Re: Should I use preconditioning ?
Yes. The fact that the compressible flow does not depend on Mach number if Mach is close to zero. I think you will get the nearly same solutions for M=0.2...0.1 (in dimensionless form)


Vajra December 12, 2001 06:39

Re: Should I use preconditioning ?
Thanks Alexey,

Could you tell me where I could find out some papers dealing with such kind of preconditioning ?


chidu December 12, 2001 13:03

Re: Should I use preconditioning ?
That would be impractical. The system becomes stiff when the Mach number tends to zero. Preconditioning is probably the best way to overcome the stiffness. A simple form of preconditioning could be Chorin's artificial compressibility method which would not require extensive changes to the code. The reference is:

Chorin, A. J., A numerical method for solving incompressible viscous flow problems, J. Computational Physics, vol 2, pp. 12-26, 1967.

If your problem has important boundary layer effects then you might need more complicated preconditioning approaches, check the work of Merkle C. L.

cheers, chidu...

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