Document Type

Conference Paper

Journal/Book Title/Conference

AIAA SCITECH 2026 Forum

Publisher

American Institute of Aeronautics and Astronautics

Location

Orlando, FL

Publication Date

1-8-2026

Journal Article Version

Accepted Manuscript

First Page

1

Last Page

18

Abstract

The simulation of a Mach 15 air flow over a blunt wedge is conducted using the direct molecular simulation (DMS) method. Due to partial dissociation of the air mixture at the imposed free stream conditions, the shock layer contains N2, O2, NO, N, and O. All potential energy surfaces (PESs) used to model the various molecular interactions only describe electronic ground states energetics. Thus, no electronic excitation is modeled. An isothermal wall boundary condition is imposed, with full momentum and energy accommodation. Two wall temperatures are considered in this work, namely 1,000 K and 2,000 K. Comparisons with computational fluid dynamics (CFD) predictions based on legacy models and chemical rates are presented. First, significant differences in heat flux predictions are observed between the DMS and CFD methods. The CFD heating data are shown to be well below the DMS results, due to a lower adiabatic wall temperature that results from differences in molecular species dissociation and NO formation. Second, in the DMS solutions, the wall temperature appears to significantly influence the chemical composition near the wall. It is observed that, for the lower wall temperature, the atomic mass fractions are smaller than for the higher wall temperature scenario, particularly for atomic oxygen. At 2,000 K, more NO depletion in the shock layer is also observed due to a hotter thermal boundary layer. No such differences are observed in the CFD results, which show near-identical chemical composition despite imposed difference in wall temperature. This could have important implications when gas-surface chemistry is accounted for, due to the differences in concentrations of highly reactive atomic constituents. The DMS solutions are shown provide a stringent test case to enhance the fidelity of thermo-chemical and transport models utilized in continuum computations, at a level of detail beyond what is possible with experimentation.

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