Correlations for aerodynamic coefficients for prolate spheroids in the free molecular regime

Abstract

A new set of aerodynamic correlations are proposed for an ellipsoidal particle in the free molecular regime by carrying out flow simulations using the Direct Simulation Monte Carlo (DSMC) method. The in-house DSMC solver is modified to be consistent with free molecular flow assumptions as well as to reduce computational cost. The solver is validated against an open-source DSMC solver, viz., SPARTA, the free molecular theory and experimental data for flow over a sphere and right circular cylinder in the free molecular regime. The flow is simulated over ellipsoidal particles at different aspect ratios, angles of attack and speed ratios to estimate the aerodynamic properties. Regression analysis is performed to give correlations for the variation of aerodynamic properties such as drag, lift and torque coefficients. The correlations are rigorously tested against the DSMC results, obtained from our in-house solver as well as those obtained from SPARTA, over a wide range of parameters.