Abstract:
For simulations of supersonic flows shock-capturing schemes have to be used.
A shock-capturing scheme produces more dissipation than a central difference
scheme. In fact, the numerical dissipation produced by shock-capturing schemes
is problematic when performing Large Eddy Simulation of supersonic flows with
shock-waves. Another train of thought is to turn the numerical dissipation to our
advantage. If the numerical dissipation of a numerical method can mimic the dissipation of the subgrid-scale(SGS) eddies, not only is SGS modelling unnecessary,
but the numerical dissipation will be a positive contribution to the calculation.
This approach is called MILES.
As a reference case, a zero-pressure-gradient, flat-plate boundary-layer flow
was chosen as there are analytical, experimental, DNS and LES results available.
The freestream conditions are a Mach number of 2.25 and a Reynolds number of
1.613 x 104/in or 6.007 x 103 based on the displacement thickness.
The central difference scheme, Osher’s scheme and Roe’s scheme are tested
for suitability in MILES. The central difference scheme is found to be numerically^
too non-dissipative without SGS modelling. Osher’s scheme is too dissipative so
that it hinders the development of turbulence. Roe’s scheme without use of a
limiter seems to have the right amount of numerical dissipation to mimic a SGS
model. Two popular slope limiters were also tested, but both affected turbulence
development when no shockwave was present.
