Numerical and Experimental Studies on the Aerodynamics of NACA64 and DU40 Airfoils at Low Reynolds Numbers

The aerodynamics of airfoils can be seen in a wide range applications. To obtain the aerodynamic loads, geometrically-scaled airfoil sections are tested wind tunnels. However, due to limited space tunnel, mismatch Reynolds numbers may lead different loads. Previous works showed that decreased lifts and increased drag coefficients associated with lower numbers, which accompanied by changes ambient flow, such as sizes separation bubbles wake vortices. Although insightful, few direct connections between pressures, flow were presented, leaving critical knowledge gap for modifications improve performances at low numbers. bridge this gap, work utilizes numerical simulations tunnel experiments study thin (NACA64) thick (DU40), two chord i.e., 4000 60,000. two-dimensional (2D) vortex particle method (VPM) varying-sized particles is used simulate unsteady compared steady-state XFOIL. As number increases, it reveals higher lift upstream suction positive pressures on upper surfaces airfoils, respectively. These explained normalized speeds Stronger pressure recoveries observed downstream reattachment points main cause reductions smaller more irregular vortices roll-up shear layers wakes similar previous experimental findings, shown make force fluctuations frequencies. Possibly missing 3D effects, results obtained from 2D VPM ‘overestimate’ effects increasing ReC = Furthermore, both XFOIL found best explaining physics angles attacks, −10°≤α≤10°, utilizing methods.