Abt: the speed of sound in incompressible flows

jinwon park

Can anyone advice me on the speed of sound? I am solving compressible flows. In doing, I have some troubles when the computation goes long. At that time, the fluid flow looks like incompressible state(i.e, density variation in space is negligible). I guess that the stability problem is related to the phase chage from compressible to incompressible. CFD people said that in incompressible state, the speed of sound becomes larger so that the CFL number needs a smaller time step size.

In this statement, I wonder followings

1. sound speed is variable or fixed. In acoustics, it is fixed at fixed temper... e.g., water is about 1500m/s

2. why compressible solver suffers from stability problems

3. Can incompressible sovler solve compressible problems?

If yes, why people has used compressible solver instead of incompressible solver which has wider application.

Thanks in advance. Before my final defense, I would like to clear this issue.