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sonVishal / CFD_Lab_SoSe_16

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Differences in pressure during simulation #1

Closed elDan101 closed 8 years ago

elDan101 commented 8 years ago

During simulation we observe large differences in pressure (up to 30 % w.r.t to 100%).

The Worksheet says:

The density ρ should always be very close to unity. If deviations occur that are higher than a few percent, something is going wrong!

However, the simulation also converges to a reasonable solution. Which we can assume to be unlikely when there are severe errors.

Do we have to investigate more, or do we find good arguments to rule it out that there is an error in the code?

At the moment this affects our default "make all" compilation, because the simulation aborts when pressure rates >3% are discovered!

sonVishal commented 8 years ago

I just started reading the worksheet and one of the first things I noticed was that for LBM we need weakly compressible flows which implies that the Mach number be << 1. In the current cavity.dat we have u_wall = 0.25 => Mach number = 0.433 which in my opinion is not << 1. I tried simulating with reduced velocity u_wall = 0.025 and I do not get any errors.