No abstract

In recent years, research is actively being conducted on unmanned air vehicles (UAVs), micro-air vehicles (MAVs), and Mars airplanes. In these flights, there is a common problem that laminar separation likely occurs due to the low Reynolds number (Re = 10 4 -10 5 ) flight conditions. Laminar separation causes a reduction in the lift-to-drag ratio and hence needs to be controlled. In this study, we utilize the "moving surface method" to resolve this problem. This method supplies momentum to the separation part and controls flow near the wing surface by actively moving the upper surface in the direction of uniform flow; the 2D effect of this method has been demonstrated in a previous study. In this study, we successfully extended this effect to 3D wings. Upon applying the moving surface method, the NACA0006 wing achieved the largest lift-to-drag ratio improvement at an angle-of-attack of 6 ° and this was achieved by the Ishii wing as well. This is because, in this method, the laminar-separation bubble disappears, thus leading to a large drag reduction. In addition, as the angle-of-attack increases, differences in the 2D flow field become prominent and a strong 3D flow field appears, even when the moving surface method is not applied; at an angle-of-attack of 9 °, many small vortices are generated, which complicates the flow field. The aerodynamic coefficient also varies; especially, the 3D drag coefficient is larger than its 2D counterpart. The moving surface method thus successfully suppresses 3D flow and flow separation, leading to a 2D attached flow field.