Design And Optimization Of Drag And Heat Reduction Scheme Of Hypersonic Re-entry Vehicle Nose-tip

The drag reduction and thermal protection systems applied to hypersonic vehicles have attracted an increasing attention because the high pressure and aerodynamic heating will cause the damage of the aircraft surface and electronic devices.It attaches profound importance to conduct a survey on drag and heat reduction scheme of hypersonic re-entry vehicle nose-tip.Firstly,aerodynamic heating and drag force in hypersonic flows are introducted.Then,research progress of experimental and numerical investigations on drag and heat reduction from domestic and overseas literatures are summarized by several kinds of mechanism,namely the forward-facing cavity,the opposing jet and their combinational configurations.Secondly,the drag and heat reduction mechanism induced by single forward-facing cavity or opposing jet scheme in open literature is investigated as a preliminary research in order to propose numerical method.SST k-? turbulent model and the first-order spatially accurate method may be more suitable for the single opposing jet scheme,and the axisymmetric assumption is also verified effective.Thirdly,the physical model and numerical method of novel combinational forward-facing cavity and opposing jet configuration is proposed.Based on the grid independency analysis,the first-order spatially accurate method should be employed,and the flow fields of each cases show stability and axial symmetry.Then,a study of performance parameter is conducted based on the numerical method proposed above.The effects of the jet operating conditions(jet total pressure ratio,species and exit Mach number),the angle of attack of freestream and the geometric dimensions(the length and diameter of cavity,the blunt lip radius,the initial expansion line)on shock stand-off distance,drag force coefficient,surface pressure and heat flux distributions are analyzed.Finally,the multi-objective design optimization of the novel combinational forward-facing cavity and opposing jet configuration is conducted to minimize both the drag force coefficient and heat transfer rate.The jet total pressure ratio and geometric dimensions are selected as design variables,and the sampling points are obtained numerically by using Optimal Latin Hypercube Design method.The Kriging surrogate model and multi-island genetic algorithm integrated in Isight 5.5 have been respectively employed to establish the approximate model and solve the pareto-optimal front.The operating conditions located on pareto-optimal front are attested to be accurate by CFD method,and higher efficiency of drag and heat reduction can be obtained than the conventional configuration.Drag and heat reduction scheme applied to hypersonic reentry vehicles has been taken as the main line,and multi-objective design optimization is the aim in this dissertation.The mechanism between hypersonic flows and combinational forward-facing cavity and opposing jet configuration is investigated,and the whole process from the verification of numerical method,performance parameter analysis to multi-objective optimization has been realized.