Conformal asymmetry nozzle design and flow field characteristics of flying wing unmanned aerial vehicle

Asymmetry nozzle of flying wing UAV(Unmanned Aerial Vehicle) was designed based on stealth and conformal requirements; this was set up into quadrilateral nozzle and circular-rectangle nozzle with different area ratios. The coupled numerical simulation was also carried out on the inflow/outflow integrated for flying wing UAV, and it is applied to studying the longitudinal aerodynamic performance of UAV and three-dimensional flow field characteristics of nozzle. Results and their analysis indicate: asymmetry nozzle of flying wing UAV can be used to improve the moment characteristic, and the lift/drag characteristic of circular-rectangle nozzle show better than quadrilateral nozzle; the convergent nozzle whose area ratio A_r≤1.0 will form the throat at the nozzle vent but not the design point expected at the engine vent, and that the strong shock will form at the throat which is not conducive for jet-flow to exhaust; with the increase of the area ratio, the axial thrust coefficient firstly increases and then decreases so that we could believe that there is an optimal area ratio, and that the circular-rectangle nozzle obtains better thrust performance than the quadrilateral nozzle along with the same area ratio; the intensity of shock wave also becomes stronger in the nozzle with increasing area ratio, and the shock wave angle formed at the root of circular-rectangle nozzle is smaller than quadrilateral nozzle which causes less blocking for jet-flow. Generally speaking, it is better to adopt circular-rectangle nozzle for the flying wing UAV with area ratio between 1.2 and 1.4; this leads to ideal aerodynamic performance.