Dear all

I write a code for compressible flow. But I want used in

low Mach number. Preconditioning is the best way to solve

my problem. But the Preconditioning is always used in

iteration process. I used approximation Godunov method, so

the code is "uniteration". Can I used Preconditioning in

my code to solve the problem at low Mach number?

I think the preconditionig leaves unchanged the steady solution, while it is not time consistent. Therefore, if you are interested in the transient solutions, you need to change your code into an iteration process, which I do not not think to be particularly taugh, but I am sceptical on its efficiency expecially if you are running 3D viscous calculation. If you look for a steady solution ... so apply it straightforwardly to your code, and you should get good results (the best suitable case is the flow around an airfoil). I would be interested in this topic, please keep in touch.

There is an alternative way to derive schemes for low mach numbers which uses asymptotic analysis. This does not require a matrix preconditioning and hence gives a time accurate scheme. See

http://citeseer.ist.psu.edu/guillard98behavior.html