Aerodynamic Environment And Fast Estimation Methods For High Speed Flight With Applications

The hypersonic flight is regarded as a new breakthrough of aeronautics andastronautics in21stcentury. In recent years the hypersonic technology has beenpromoted from conceptual and principal investigation phase to vehicle design anddevelopment phase. As one of the key techniques, engineering methods foraerodynamic prediction have been employed in many applications for conceptual andpreliminary design of hypersonic vehicles. Therefore it is necessary to establish asoftware platform which can predict the aerodynamics and aerodynamic heatings oncomplex three-dimensional vehicle very fast.The uncontrolled spacecraft like deorbited satellite or upper stage of spent rocketreenters the earth’s dense atmosphere at the end of their life. The strong aerodynamicand aerothermal loads can melt and break the structures into many pieces of debris,and the surviving ones can cause great risk to the ground. Debris reentry prediction isone way to mitigate the underlying hazard. It should be of great importance to build asoftware system to predict debris reentry based on engineering methods.This thesis focuses on the aerodynamic environment of hypersonic vehicles, theestablishments of hypersonic aerodynamic and aeroheating predition platform, theaerodynamic models for simple objects and debris reentry analysis and riskassessment system.Firstly, the aerodynamic environment of hypersonic vehicles is introduced,including the distributions of non-dimensional flow parameters and criticalaerodynamic lines in a velocity-altitude map. Then integrated analysis ofaerodynamic environment for cruising hypersonic vehicles and reentry debris will begiven. A new concept of ‘soft flight’ is proposed for the first time based onaerodynamic environment analysis.We establish the hypersonic aerodynamic and aeroheating predition softwareplatform via methods based on surface grids and streamlines. For continuum flow, thesurface pressure is calculated by methods of Newtonian flow model and others, and the aerodynamic heating is computed along surface streamlines using approximateboundary layer solutions. For free molecular flow, theoretical formulae by solvingcollisionless Boltzmann equation using the Maxwell equilibrium gas distribution areadopted. For transitional flow, we use bridging relations. The aerodynamic propertiesare calculated and validated for several typical configurations, comparing withexperimental data or CFD results. According to the validation work, we performfurther discussions and conclusions on some vital factors which may influenceprediction accuracy.The aerodynamic models for simple objects are proposed. The models arevalidated by CFD or DSMC computations. Based on the aerodynamic models ofsimple objects, we build the software system for debris reentry and risk assessment.The system can predict the reentry of hundreds of distinct debris at the same time inseveral minutes. Compared with other similar tools like DAS and ORSAT, presentsoftware system provides models for more object shapes.