NUMERICAL PARAMETER INFLUENCE
ON BUMP TEST
this part of the project, the study has been made with the test-case Bump
which will be describe later. We have tested particularly the influence
of two parameters: the CFL number and the artificial viscosity.
Their influence will be evaluated by looking at convergence of each different calculation.
The Bump test is a computation
on half profile whose geometry is showed in the next figure representing
the mesh used for the calculation:
Unstrctured mesh used in Bump calculation.
Tests were made with the
Mach incidence number taken equal to 0.85 in every calculation.
The following figure represent the shock on the bump in one of our tests:
Mach number evolution on the bump.
We will now study the influence of the cfl number and of artificial viscosity.
This figure shows that an increase of the cfl number improves the calculation speed. This result was expected. However, it is impossible to increase the cfl too much because it has a limit. Upper that limit the computation may diverge.
By looking at this figure,
we can easily conclude that an increase of artificial viscosity improves
convergence of the calculation (about two orders in precision in this case). Nevertheless, a too high artificial viscosity may disturbs the reality of the physical problem. During the next tests, we will use an artificial viscosity
equal to 0.2 because its precision appears efficient for our studies.