Experimental Validation of Virtual Wind Tunnel Testing for Ultra-low Reynolds Numbers Flows

The recent success of the Ingenuity Mars helicopter developed by the jet propulsion laboratory (JPL) demonstrated the feasibility of the Martian flight. Low pressure (660 Pa) and temperature (210 K) characterize the ground-level Martian atmosphere. Since such conditions are difficult and expensive to mimic on Earth, it is necessary to have reliable simulation tools that can correctly reproduce Martian aerodynamics. In the case of unmanned aerial systems (UAS), the latter is characterized by a high subsonic Mach number at the tip of the blades and an Ultra-low Reynolds number regime. To this purpose, the laminar solver embedded in the commercial CFD code STAR CCM+ was validated by reproducing experiments carried out in the Martian Wind Tunnel at Tohoku University using a triangular airfoil wing at Reynolds 3000 and a Mach number of 0.5. Simulations are performed at angles of attack ranging from 0 to 16 degrees showing a satisfactory agreement with experimental results for very different flow conditions.