Drag Model for Nonspherical Particles in Supersonic Flow

A new drag model is developed for nonspherical particles in supersonic flow. The proposed model modifies a physics-based drag coefficient for a sphere in supersonic flow with an effective length scale that has been well characterized for nonspherical particles in subsonic flow. Two geometric parameters are needed for this length scale: the Smoluchowski radius and the projected area. Both quantities are easily calculable using statistical methods and can be determined for any nonspherical shape. The model is validated with fully resolved computational fluid dynamics (CFD) and direct simulation Monte Carlo (DSMC) simulations, showing increased accuracy in the orientationally averaged drag force when compared to existing approximation methods for nonspherical particles. Finally, particle trajectories are simulated for two high-speed flow scenarios, indicating that, for small atmospheric particles, the proposed drag model will decrease impact kinetic energy, surface erosion, and recession rates compared to the existing particle approximation methods.