Role of RANS, Hybrid and LES for Wing Flow Simulations at Relatively Low Reynolds Numbers

Two types of recent results for the simulation of wing flows at relatively low Reynolds numbers are presented. One is a series of the flow simulations over simple wings, which eventually help the wing design of Mars flyer. The other is a series of the similar wing flow simulation but with DBD plasma actuator that reduces flow separation. Simulations are conducted with highly accurate spectral-like compact difference scheme that reduces the number of grid points with keeping same spatial resolution. With this method, iLES is used as a main analytical tool for the simulations. There appears strong Reynolds number effect and small change of the Reynolds number may drastically change the aerodynamic characteristics especially for thick wings. Thin wing has linear lift characteristics similar to thick wings at high Reynolds numbers, but flow structure is totally different from so-called potential flows. Wing flow simulation but with DBD plasma actuator shows that iLES captures flow structure induced by the DBD plasma actuator and transition to turbulent flows may be one of the important factors of the flow control by these devices. It is also shown that both flow separation and flow reattachment are the key factors for the simulation examples presented here, which requires LES type of simulations.