Aerodynamic interactions at low Reynolds number slipstream with unsteady panel/viscous vortex particle method

An unsteady panel/viscous vortex particle hybrid method, with the consideration of air viscous and compressibility effects at low Reynold number, is developed base on equivalent vorticity principle and Neumann boundary condition to rapidly calculate the aerodynamic interaction between the wing and the propeller of the solar-powered airplane. Experimental data are compared with computation method to validate the hybrid method proposed. The aerodynamic interactions between the propeller and the wing are investigated at different installation positions and working conditions. Calculated results indicate that the distribution of the spanwise and the chordwise pressure are apparently changed by the increased axial velocity and upwash and downwash effects induced by the propeller slipstream to lead to a decrease of lift-tot-drag ratio. A larger chordwise distance and a higher vertical installation position can reduce propeller thrusts, and can also decelerate lift-to-drag ratio of the wing. For the case of multi propeller interactions, different rotation directions cause different aerodynamic characteristics of the wing. When the propeller rotation direction is opposite to the wing tip vortex direction, the propeller slipstreams can counteract vortex strengths at the wing tip to induce an augment of lift-to-drag ratio of the wing.