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theses

There is a reinterest in hypersonic flow. There are several programs all around the world to produce hypersonic aircraft. Computational fluid dynamics (CFD) is an essential tool for high speed aerodynamics. However, it is still under investigation that how reliable is this tool especially at high stagnation enthalpies at high speed flows where non-equilibrium effects are important. For assessment of the CFD capability in the prediction of the aerothermodynamic loading (surface pressure and surface heat transfer) on a hypersonic vehicle, three sample experiments are examined in this dissertation. The models include a hollow cylinder flare, a double cone, and a hemisphere at Mach number range of 10.9 to 14.6. The laminar shock wave boundary layer interaction is investigated at high enthalpy ranges of 9.65 to 21.85 MJ/kg. It is shown that the formation of a supersonic jet as a result of the interaction of the shock waves prevented the highly dissociated gas to reach to the surface and thus the thermally perfect gas model has the best prediction of surface pressure and heat transfer. For hollow cylinder flare, the shock wave boundary layer interaction is weak and therefore, the effect of non-equilibrium modeling is negligible.

The Edney III type shock-shock interaction is studied over a hemisphere at low enthalpy of 2.1 MJ/kg. Edney III interaction can create a region of high pressure and heat transfer over the surface. Therefore, accurate prediction of this phenomenon is essential. The study in this dissertation shows that the interaction is very sensitive to the location of the interaction of the impinging shock and the bow shock. This can change even the flow regime from laminar to turbulent.

Another challenge facing scientists in producing a hypersonic vehicle is how to rapidly maneuver the vehicle. The common controlling methods are too slow and during their actuation time, the vehicle moves several times its length. One option is to use energy discharge to change the flow structure around the body. This changes the pressure distribution over the body which can create pitching moments for steering the vehicle. Drag reduction is also another benefit that can achieve from energy deposition. If the energy discharge is on the axis of symmetry of the body, only drag reduction is acquired; however, off axis energy discharge provides drag reduction, side force and thus pitching moment. This dissertation has shown that the drag reduction and pitching moment depend on the amount of energy deposited, the location of the discharge, and the shape of the body.

ETD_10736

Ph.D.

Includes bibliographical references

doi:10.7282/t3-b3q3-3g45

ETD doctoral

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