Optimal Design And Active Flow Control Of Half Flush-mounted S-duck Inlet

In an effort to achieve the economic and environmental goal of the future aircraft, NASA has launched the Ultra Efficient Engine Technology (UEET) program. One of the key technology of this program is the Blended-Wing-Body(BWB) airplane with the use of a half flush-mounted engine, which has a larger aerodynamic lift, a smaller aerodynamic drag and better commercial benefits. This novel configuration and its benefits attract the focus of home and abroad researchers. The BWB adopts the half flush-mounted S-Duck inlet which is integrated on the rear of the vehicle. As a result, the inlet ingests large mounts of boundary layer developing on the wing, whose thickness is about 29 to 36 percent of the throat height of the inlet. Thus the total pressure recovery coefficient reduces, and the circumferential distortion coefficient and swirl distortion coefficient rises, so the performance of the inlet decreases. In the present paper, in order to improve the performance of the half flush-mounted S-Duck inlet, the optimization design and active flow control technology were applied to the inlet.Firstly, for the purpose of improving the accuracy and effectiveness of the numerical simulation, the grid independence and the reasonable turbulent model was studied in the computational domain covering the internal and external flow field. The results show that about 1.27 million meshes meet the requirement of grid independence and the Realizable k-εturbulent model is appropriate in this simulation.Secondly, to facilitate the geometry parameterization of the inlet, the Hicks-Henne functions were used as the basis functions to formulate the variations of the centre line and the cross-sectional area. The optimization software ISIGHT, as well as Matlab, Gambit and FLUENT were combined to build the optimization platform. Through optimization calculation, the total pressure recovery coefficient increases by 0.8 percent, and the circumferential distortion coefficient reduces by 30 percent. The performance of the inlet is improved.Thirdly, to further improve the inlet performance, the active control flow technology such as sucking and blowing was applied. The variation of the inlet performance was studied under different suction/blowing locations and different suction/blowing mass flow rates. The results show that suction flow control method is an effective way to reduce the circumferential distortion coefficient. The ideal suction place locates before the boundary layer separation, such as lip location.At last, based on the research of suction or blowing only, a control method which combines the suction and blowing was attempted. For the inlet investigated in this paper, the effect of the combined control is better than the blowing only but worse than the suction alone, which infers that the combined control is not the simple superposition of suctioning and blowing.