New Modeling Method for One-Dimensional Simulation of Hypersonic Flows

What is it about?

Most aerodynamics modelers use computational fluid dynamics (CFD) codes, as they are highly efficient and well validated. CFD makes use of the continuum assumption, where molecules are presumed to collide frequently enough for a number of approximations to be made. However, the continuum assumption breaks down at high altitudes, where air is so thin that collisions between molecules become infrequent. Despite their higher computational cost, for physically accurate results, kinetic modeling methods must be used. This paper presents a new model for one-dimensional simulation of a hypersonic flow for the discrete-velocity kinetic modeling method (DVM). Results are validated against another kinetic modeling method, and new insights about kinetic hypersonic flow behavior are revealed.

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Photo by Othman Alghanmi on Unsplash

Photo by Othman Alghanmi on Unsplash

Why is it important?

The work derives a numerical model for a hypersonic stagnation streamline for discrete-velocity methods (DVM) and provides clarifications, guidelines, and appropriate test cases for testing the stagnation streamline model in either DVM or Direct Simulation Monte Carlo (DSMC). Kinetic modeling methods such as DVM and DSMC are becoming increasingly important in the hypersonics community as vehicle flight regimes increase in altitude and speed (where computational fluid dynamics codes fail). DVM is especially increasing in importance as its deterministic solutions cover many weaknesses of the conventional DSMC method. However, the computational cost of multi-dimensional DVM can be prohibitive for some users. Thus, a one-dimensional model such as a stagnation streamline improves the viability of DVM as a tool for hypersonic flowfield analysis. This work also highlights unique characteristics of the particle velocity distribution function (VDF) present in stagnation streamlines. These VDF results were not observed in previous computational and experimental studies of normal shocks, and warrant further consideration from experimentalists and chemistry modelers.