HIGHLY EFFECTIVE SIMULATION MODELS IN ANALYZING AERODYNAMICS OF AIRFOILS AT LOW REYNOLDS NUMBER

Abstract

Recently, much work has been conducted for airfoils at low Reynolds and high velocity for further improving design airplanes those can fly on Mars and on stratosphere of the Earth. In this study, the aerodynamic characteristics of a typical airfoil shape named Ishii are studied by numerical approach for understanding the aerodynamic forces and flow fields at different angle of attack and Mach number. To reduce the numerical time, the Reynolds averaged Navier-Stokes equations are used for the simulation. The numerical results are compared with previous experimental data at the same flow conditions. This study found that the turbulent model should be changed from k-ω SST for angles of attack below 8° to k-ε model for higher angles of attack to obtain the accurate results. The maximum difference between simulation and experimental results is less than 9%. To extend the results, the aerodynamic characteristics were investigated for angles of attack from 0° to 20° and the Mach number between 0.2 and 0.8. The effect of serration at the leading edge on aerodynamic characteristics was also investigated. The results of the current study show that the angle of attack with maximum lift coefficient is around 8° at M = 0.2 and it increases for increasing Mach number. At high angle of attack, the lift decreases but large stall does not occur. The reason is from the generation of a separation bubble at leading edge of airfoil, which shows different characteristics from normal airfoil model. The serration at leading edge increases lift and aerodynamic performance for angles of attack above 8°. The results of the proper orthogonal decomposition indicates that the unsymmetric flow with a large wake structure is the most dominant flow at high angles of attack. The flow pattern of those modes, velocity and pressure distributions around the model are discussed.