Numerical Analysis of Flow Field and Aerodynamic Characteristics of a Quadrotor

In this paper, the flow field and aerodynamic characteristics of a quadrotor are studied via three cases of numerical simulations: First, the flow field around a hovering quadrotor is simulated; second, the case with a side wind is simulated; finally, the flow around the quadrotor and its motion are simulated via motion-coupled flow computation. In the first case, it is found that the downwash generated by each blade is strengthened mutually and that the Cp distributions on the blade upper surface vary according to the blade position, causing periodic, 5% of thrust oscillations. In the second case, it is found that the positive pitching moment acts on the body. This moment is partly created by reduced thrust from downstream rotors that receive flows already directed downward at upstream rotors, and hence, having effectively decreased angles of attack. The final case shows that, due to the pitching, the quadrotor is unstable in the side wind condition until it reaches an almost vertical attitude. It is demonstrated that the present motion-coupled flow simulation serves as a powerful tool to reproduce and understand behaviors of quadrotor flights.