Numerical Investigation On The Drag Reduction Of Aerospikes In Series For Hypersonic Vehicle

By installing aerospikes, the structure of bow shock in front of hypersonic vehicle is changed effectively, the drag force and heat flux is reduced obviously. The structure of flow around vehicle turn to be more complex with the interaction of shocks, expanding waves and backflow regions when aerospike is considered. Currently, the related investigation focused on the area of vehicle with single aerospike. However, aerospikes in series is discovered to be more effective, and it has great significance in both theory and application to investigate characteristics of the drag resistance, wave and vortex structures in flow field.In this thesis, hypersonic flow over a blunt body is simulated, in which both of single aerospike and aerospikes in series on the front are considered, and the effect of drag reduction and influence factors are investigated in detail. Both of the flow field of aerospikes in series and single one are studied and compared, the drag reduction effect of different shape character of aerospikes in series is studied, and the relationship between attack angle and the effect of drag reduction is analyzed. The study includes the following aspects:A numerical method to compute the aerodynamic drag force and flow structure of supersonic is developed by solving Navier-Stokes equations. Numerical simulations of a supersonic free-stream at Mach number of 6.5 over a spherical body with single aerospike is carried out for testing the numerical method in this thesis by comparing with experimental result in reference. Then, flow structure over aerospikes in series is analyzed compared with that over single one and the drag reduction mechanism is presented. As a result of which, a conclusion is proved that aerospikes in series show better performance in drag reduction than single one.The cases with four different kinds of typical front aerodiskes, which include tapered nail, flat nail, dome nail and hemisphere dish, are simulated in order to find the best front aerodisk shape. According to analysis, hemisphere dish is picked out to be optimal shape of front aerodisk in the following investigation. After that, several cases of aerospikes in series with different length and/or size distribution are considered. According to the analysis of wall surface pressure distribution and the variation of drag force coefficient on the vehicle, the relationship between the drag reduction effect and aerospikes in series is obtained.The cases of supersonic flow over blunt body with different attack angle are simulated. As a consequence of analyses to the pressure distribution of wall and flow structure, it is proposed that the relationship between the drag reduction effect and attack angle. With consideration of the drag reduction effect and lift force of the blunt body with aeroapikes in series, an optimal attack angle is present with the considered flight condition.The results obtained in the thesis provide important theoretical support and reference on drag reduction of hypersonic vehicles and aerospikes design in engineering applications and related experimental studies.