Mach 15 blunt-wedge DMS: wall temperature changes near-wall atoms

What is it about?

We simulated Mach 15 air over a blunt wedge with direct molecular simulation (DMS) on first-principles potential energy surfaces (electronic ground states only: N2, O2, NO, N, O). The wall is isothermal with full accommodation, at 1,000 K and 2,000 K. Compared with CFD that uses legacy chemistry, DMS predicts substantially higher heat flux, because CFD’s adiabatic wall temperature is too low (different dissociation and NO formation). In DMS, wall temperature also changes the near-wall composition, especially atomic oxygen and NO; the CFD fields look almost the same at both wall temperatures.

Featured Image

Why is it important?

If continuum CFD cannot see wall-temperature effects on atomic species, it will mis-set the boundary condition for any gas–surface chemistry. DMS here is a numerical experiment at a level of detail a wind tunnel cannot provide, and it is a hard test for the thermochemical and transport models inside production CFD.

Perspectives