Aerodynamic Investigation of Crow Flap Control System in a Flying Wing UAV Aircraft

In this research, one of the widely used control systems of tailless aircraft, named Crow Flap, has been simulated by numerical method and the appropriate opening direction of this system has been investigated. By creating a differential drag on both sides of the aircraft, this system creates the necessary yawing moment and directional control. This system consists of two moving surfaces that are deflected against each other to neutralize each other's force and produce drag. One of the important issues in control systems is the reduction of disturbing moments. Determining the suitable opening direction with the least drag and disturbing moment and increasing the useful moments is the aim of this research. For this purpose, the measurement of these moments and forces are compared in two states of normal and reverse-opening. The UAV under investigation is a lambda-shaped UAV named Swing. Experiments have been carried out at AOAs of 0 to 12° for three opening angles. The created Mesh is unstructured. In this simulation, the continuity, momentum, and scalar equations have been solved by the Simple C algorithm after discretization with the finite volume method, and the turbulence model (K-ω-SST) has also been used. In this research, the opposite opening direction of the Crow Flap, unlike the usual opening direction mentioned in some articles, had a better result, so that at high AOAs, this opening direction has between 5 and 32% less drag and it has produced 10.5 to 35% more Yawing moment along with reducing disturbing moments.