Roughness effect on airfoil aerodynamic performance for land-yacht robot

Abstract

The land-yacht robot presented in this paper aims at an Antarctic expedition which is driven by wing-sail. The wing-sail is composed by airfoil and surface roughness, which is one of the main factors affecting the aerodynamic performance of the airfoil. In order to improve the efficiency of the airfoil, stress analysis of the wing-sail and airfoil mechanism is researched and the type of airfoil is determined. For roughness size, equivalent particle roughness is introduced and a boundary layer flow separation model is a simulated roughness model. Then N-S equations and the S-A turbulence model are predicted airfoil aerodynamics in CFD (Computational Fluid Dynamics). When different sizes of a roughness strip are deposed on an airfoil surface, we obtain lift and drag coefficient, sensitive angle of attack of 6°, and 0.5 mm of sensitive roughness size. When roughness is arranged at different positions, we discover two sensitive positions, 10% chord length in suction surface and near trailing edge in pressure surface. Further analysis of the two sensitive positions in 10% chord length and aerodynamic is worse with the increasing roughness size. Near the trailing edge, there is a threshold of 0.7 mm. Lower than 0.7 mm, aerodynamics is improving; in contrast, it is worse. Finally, simulation results are verified by experiments. It shows that the predicted value conforms to the experiments and this research can provide a valuable reference for the mechanism of the land-yacht robot.