Study On The Aerodynamic And Aero-heating Basic Problems Of Hypersonic Nonuniform Blunt Waverider

Waverider is one of the important candidates for hypersonic flights owing to its better aerodynamic performance than conventional configurations under high speed conditions. During the practical application, since the limitation of manufacturing, the sharp leading edge of ideal waverider is difficult to be obtained; meanwhile, the phenomenon of ablation would be induced by the serious aero-heating along the sharp leading edge; the geometry and aerodynamic performance of hypersonic vehicles would be changed. Furthermore, an invalidation of its control system would take place and the whole mission of hypersonic flight would be failed. Thus, for the hypersonic vehicles which are designed based on waverider configuration, it would be a key problem to solve the conflict between its good aerodynamic performance and serious aero-heating / control environment which are induced by the infinite sharp leading edge.Blunting is thought to be an effective method to degrade serious aero-heating on the surface of hypersonic vehicles. Unfortunely, the attachable shock around ideal waverider would be insteaded by bow shock if the leading edge is blunted, which would reduce the lift-to-drag ratio seriously. In this paper, a concept called “Nonuniform Blunt Waverider” is proposed. Taking the nonuniform aero-heating characteristics into accont, if the mechanism of blunting and bluntness impact on the aerodynamic and aero-heating performances of waverider configuration can be studied sufficiently, different blunt radius can be used along the leading edge of waverider; therefore, the aerodynamic performance might be improved after blunting with a satisfying thermal protection system design.Based on this concept, some foundational problems and key technologies have been investigated in the present paper under the background of hypersonic gliding vehicle(HGV) with waverider configuration and skip-glide trajectory.In this paper, the three-dimensional dynamic model has been built to analysis the impact of high lift-to-drag ratio configuration on the flight performance of HGV, and the problem of waverider design can be implied according to the discussion. Based on the cone shock flowfield, an optimal investigation about the ideal sharp waverider has been done with the consideration of viscous effect and by the method of multiobjective evolutionary algorithms. The optimal objectives include lift-to-drag ratio, volume efficiency and volume. A clear object has been built for the further study.In the flowfield around waverider, the scale of leading edge is small while its curvature is quite big; the flow phenomenon is also very complex, such as shock wave, boundary layers and so on. In order to obtain a rational mathematical physics model for the study of waverider, not only the rarefaction effect, but also the high temperature effect and viscous effect have been investigated in details. Moreover, the numerical methods, including the governing equations, the space/time discretize schemes and the computational grids used to solve the physical model have been studied and given in the present context. Three typical cases have been chosen and investigated to insure the validity of numerical algorithm.In Chapter 4, the blunt method of “adding material” which is proposed by Tincher has been proved to be better for the modification of waverider due to the comparision of many performances, such as volume, volume efficiency, lift and drag coefficients, lift-to-drag ratio, maximum heat flux, maximum temperature and so on. Based on this blunt method, the mechanism of blunting and bluntness impact on the flow structure, aerodynamic and aero-heating performances has been deeply studied by using CFD techniques. According to the differences of flow characteristics, the leading edge of waverder can be divided into three typical parts. For the stagnation point, leading edge and nose region, the flow characteristics and impact mechanism in the flowfield around and on the configuration have been deeply investigated in Chapter 5. An ellipse stagnation-point model has been built for waverdier; the gemotry factors which impact the aero-heating characteristics of leading edge have been carefully analyzed; moreover, the relationship of heat flux between the nose region and stagnation point has been obtained. These new methods of predicting the aero-heating at the stagnation point, leading edge and nose region have supplied a theoretical support for the concept of “Nonuniform Blunt Waverider”.Furthermore, the detailed design method of “Nonuniform Blunt Waverider” has been introduced in Chapter 6, and the local sweepback angle is suggested to be the factor which can distinguish the three parts of leading edge. Using CFD techniques, the three-dimensional flow structure, aerodynamic and aero-heating performances have been obtained in details for two waveriders with uniform and nonuniform blunt methods respectively. By the experiment carried out in hypersonic shock wind tunnel, the schlieren photo and test data have been obtained for two waverider models. Based on the numerical and experimental results, the predict models, the flow characteristics and impact mechanism obtained by theoretically analysis have been verified further; moreover, the concept of “Nonuniform Blunt Method” has been proved be feasible for hypersonic waverider design.In the present paper, more attention has been paid to the influence of attack angle and sideslip angle on the performances of blunt waverider under off-design conditions with the consideration of paractical application. The conclusions obtained in Chapter 7 can also give some advises about flight attitude limitation during the trajectory optimazition and control system designs.A new concept of “Nonuniform Blunt Waverider” has been proposed and much work has been done to study the relative basic scientific problems and key technologies. For hypersonic vehicles, some useful suggestions can be obtained for the un-ablation thermal protection system design, the trajectory optimization design and control system design based on the conclusions of this paper. The studies carried out in the present context might promote “waverider” from an academic concept into a pratical hypersonic vehicle further.