Ροές υψηλών ταχυτήτων και θερμοδυναμική αερίων σε υψηλές θερμοκρασίες

Abstract

The object of the present doctoral thesis constitutes the theoretical and calculating simulation of high-speed atmospheric flightmotion, with particular emphasis in hypersonic speeds and aerodynamic and thermodynamic analysis. The methodology that is followed has as main aim the prediction of return flight trace of hypersonic vehicles in Earth’s ground, assuming the speeds of flight to reach the 15000 m/s (Mach number ~ 40) and stagnation temperatures the 15000 K. In this work are followed methodological approach and systematic bibliographic research in the scientific field of aerodynamic overheating that suffers Hypersonic Vehicles(H/V) at their flight in Earth’s atmosphere. The analysis of hypersonic flow, thermal loads and new methods for thermal protection systems of H/V are developed the last decades and are evolved continuously, but until today (2008) resulting failures mainly at their reentry in atmosphere from the interval. For the simulation of the atmospheric hypersonic flight motion become study and analysis of thermodynamic properties and parameters, that characterize the flow fields in high speeds and high temperatures. The determination of altered flow conditions, thermodynamic properties and transport magnitudes will contribute in the theories of modelling and high thermal strain calculations, in the constitution of overheating air and it’s high temperature determination in the external surface of heat insulation wall of high-speed vehicles at their flight in Earth’s atmosphere. In this work are developed calculating algorithms of simulation for the successful prediction of atmospheric flight motion of hypersonic transport vehicles. The basic aerodynamic characteristics of lifting vehicles in high speeds are calculated with suitable adaptation of classic Newtonian Flow in high speeds and are confirmed with experimental data of aerodynamic measurements in high speed wind-tunnels of NASA. Moreover in this thesis are incorporated models for the simulation of properties of overheating air behaviour as real gas in thermodynamic balance in extreme flow conditions (high speeds, high pressures and low densities). Particularly becomes analysis of the altered constitution and properties of air (thermodynamic magnitudes and transport magnitudes) in very high temperatures on hypersonic flow field. This study will lead to the export of a new model for the transported thermal stagnation region calculations of hypersonic vehicles, which is confirmed so much with internationally recognized thermal models (as that of Fay-Riddell) and with calculating simulations of other researchers. The methodology that is followed will constitute the base for the export of a new theoretical model for high temperature air calculations in thermal protection systems surface of hypersonic vehicles. The effectiveness of proposed methodology, with the combination kinematic and aerothermodynamics analysis in united calculating algorithm, is proved and confirmed via the application of above simulation models on ballistic (Apollo Command Module) and lifting (Space Transportation System, known as Space Shuttle) hypersonic vehicles. The results of proposed method are compared, evaluated and certified with similarly by internationally recognized calculating systems and experimental data of measurements in hypersonic wind-tunnels for high speed vehicles. In the next decades, the development of hypersonic transportation systems will be rapid and particularly attractive from technological side with hopeful messages for “earthy” transfers with high speeds in short times, but also likely persons-astronaut missions in other planets of solar system. Thus the present doctoral thesis, developing the progress that has taken place in the past few years, is appreciated that it contributes substantially in still under development - for the Greek data unusual - scientific field of Hypersonic Aerothermodynamics, and in the growth of methodology for the aerothermodynamic construction of hypersonic vehicles. The proposed complex model of kinematic and thermodynamic calculating analysis and it’s methodology that is followed have influence and application in the majority of cases of hypersonic flights in earthy and, with properly adaptations, in anyone planetary atmosphere. Of course, the proposed methodology has margins of development and growth in order to improve her efficiency with the import of also new elements and also extended the spectrum of her possible applications.