Study of aerodynamic coefficients dependency on reynolds number for subsonic flow conditions

Abstract

Aerodynamic coefficients play a key role to determine the behavior of a flying vehicle along its trajectory for a particular mission. Prediction of these aerodynamics coefficients can be made through experiments, analytical solution or Computational Fluid Dynamics (CFD). These coefficients are determined for a wide range of Mach numbers and angles of attack at different altitudes. During flight, Mach numbers may be similar at two (or more) different altitudes. However, Reynolds number can be different at each altitude due to the variation of density and temperature with altitude. In present work, the dependency of aerodynamic coefficients on Reynolds number is studied for subsonic flow conditions. For this purpose, simulations are performed on 3D half body of HB-1 test case with 2nd order coupled steady state solver and k-ω SST turbulence model. Simulations are performed for Mach numbers 0.6 and 0.8 for altitudes (sea level to 70 km) and angles of attack. Axial force, normal force and pitching moment coefficients are determined. Results show that axial force coefficient varies significantly with Reynolds number for a fixed Mach number. Variation in normal force and pitching moment coefficient is insignificant for smaller values of angle of attack. However, at larger values variations are significant. Results show that low subsonic regimes are more affected by Reynolds number. For validation purpose numerical results are also compared with experimental data of HB-1 test case.