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

• Published in: Computers & fluids 2021-06, Vol.223, p.104934, Article 104934
• Main Authors: Chinnappan, Arun K., Kumar, Rakesh, Arghode, Vaibhav K., Kammara, Kishore K., Levin, Deborah A.
• Format: Article
• Language: English
• Subjects: Aerodynamic coefficients; Aerodynamic correlations; Aerodynamics; Angle of attack; Aspect ratio; Circular cylinders; Coefficient of variation; Collisionless DSMC approach; Direct simulation Monte Carlo method; Flow simulation; Free molecular flow; Free molecular regime; Molecular flow; Molecular theory; Prolate spheroids; Regression analysis; Solvers
• ISSN: 0045-7930; 1879-0747
• DOI: 10.1016/j.compfluid.2021.104934

•In this novel work, we have proposed new correlations for aerodynamic coefficients, such as coefficients of drag, lift and torque, for an ellipsoidal particle in the free molecular regime.•To this end, a large number (∼37,000) of DSMC calculations have been carried out for flow over an ellipsoidal particle using our in-house DSMC code, modified to work in free molecular regime.•The variation of aerodynamic coefficients is obtained with respect to speed ratio, angle of attack and aspect ratio of the geometry.•Using the results, a set of correlations have been proposed for the aforesaid aerodynamic coefficients by performing regression analysis.•The correlations have been rigorously tested against the DSMC results over a wide range of parameters.•The best knowledge of authors, this is the first time, such an attempt has been made. 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.