Study On Modeling、Analysis And Validation For Hypersonic Vehicle

Hypersonic vehicle has a slender body, waverider design,and the scramjetengine is under the vehicle body. Such vehicle flies in near space where theatmosphere is thin and complicated. Unlike conventional aircraft, the propulsionsystem of hypersonic vehicle is highly integrated into the airframe, which will causestrong couplings between the airframe and propulsion system. High-speed flight,flexible structure and low natural frequency can result in the bending of fore-body andaft-body of vehicle which will affect the airflow characteristics through the inlet andexit of the engine and hence the aerodynamic layout on the vehicle surfaces.Furthermore, the highly couplings among the aerodynamics, flexible structure andpropulsion system with the viscous effects, the varying flight condition, hightemperature gas effects and shear layer effects make the modeling and control of suchvehicle very challenging.The emphasis in this thesis is focused on the studies of the modeling and modelvalidation of a typical hypersonic vehicle.1. For a rigid hypersonic vehicle, by the analysis of the flow characteristics onthe surfaces and the engine performance, Oblique shock and Prandtl-Meyer flowtheory, quasi-one-dimensional relation and momentum theory are used to calculate theaerodynamic forces,moments and the thrust.Then a physics-based model of the rigidhypersonic vehicle is presented. According to the model, the pressure distribution ofthe vehicle surfaces and inner engine, the trend of lift, drag, pitching moment andthrust with angle of attack, Mach number and throttle are analysed.2. For a flexible hypersonic vehicle, we assume that the vehicle is a free-freebeam, the assumed modes method is used to compute the natural frequencies andmode shapes of the flexible structure. Considering the fore-body deflection andaft-body deflection which are caused by the deformation of the vehicle body, theaerodynamic forces and moment are calculated by Oblique shock and Prandtl-Meyerflow theory, piston theory and Eckert’s Reference Temperature Method,whichincluding the unsteady flexible effects and viscous effects. Then a physics-basedmodel of the flexible hypersonic vehicle is presented. According to the physics-basedmodel, the effects of the flexible and viscosity to the aerodynamic are analysed. 3. Based on the physics-based models, simplified curve-fitted models of the rigidand the flexilbe hypersonic vehicle are presented with the curve-fitted approximationsmethod,and the flexible model has the couplings of the rigid-flexible modes by thecomparison of the dynamic modes between the rigid and flexible model.Thecurve-fitted models are the simplification of the physics-based vehicle model, whichcan not only reduce the complexity of the model, but also retain aero-flexiblestructure-propulsion interactions of the physics-based model.4. By omitting the weak terms in the curve-fitted model, control-oriented modelswhich can be applied to the control design are presented. For the control-orientedmodels whether or not can match with the curve-fitted models, quantitativeassessment methods which based on frequency domain and wavelet domain arepresented to validate the dynamic performance consistency of the models. Hypothesistest and Monte Carlo significance test are used to make quantitative verification ofconsistency on the control-oriented models and the curve-fitted models.