A new methodology has been developed for the design of hypersonic scramjet inlets using gas dynamic relations. The approach aims to find the optimal inlet geometry which has maximum total pressure recovery at a prescribed design free stream Mach number. The design criteria for inlet is chosen as shock-on-lip condition which ensures maximum capture area and minimum intake length. Designed inlet geometries are simulated using computational fluid dynamics analysis. The effects of 1D, 2D inviscid and viscous effects on performance of scramjet inlet are reported here. A correction factor in inviscid design is reported for viscous effects to obtain shock-on-lip condition. A parametric study is carried out for the effect of Mach number at the beginning of isolator for the design of scramjet inlets. Present results show that 2D and viscous effects are significant on performance of scramjet inlet. Present simulation results are matching very well with the experimental results available from the literature.

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Flight testing of a military low bypass turbofan engine involves multitudes of tests to ensure the Engine - Aircraft compatibility across the flight envelope. One of the safety critical tests is to conduct In-Flight restart of the engine. Detailed planning and careful execution is mandated for a single engine aircraft. Accurate modelling of sub-idle performance characteristics of the engine during windmilling conditions enables better prediction of engine behavior during in-Flight shutdown and restart. Typically, Engine manufacturer provides a Performance Cycle Deck (PCD) to predict and assess the performance of the engine across the flight envelope for all throttle positions. However, the PCD does not include sub-idle behavior. The present work focusses on developing a torque based engine behavior model which enables prediction of time dependent fan and compressor characteristics during sub-idle operations. The proposed model is divided into two parts. The first part deals with deceleration characteristics during engine shut-off and spool down, and the second part deals with the acceleration characteristics during spooling up and engine restart. In-flight spool-down (a quick relight without windmilling) restart data obtained through flight tests was used to validate the present model. The model is intended to be used for future flight tests which include windmill restarts under various operating conditions. The model is expected to accurately predict the correlation between aircraft speed and engine windmilling rotor speeds for arriving at a windmill restart envelope for the aircraft.

Computational Fluid Dynamics (CFD) analysis has been carried out on ballistic bodies with a hemispherical aero-disk spike. This research involves the presence and absence of a blunt tip to understand the flow behavior on these bodies under two scenarios namely zero-degree angle of attack and at supersonic speed (Mach 2.0). The aerodynamic drag and thermal heat transfer effects of these spikes on three different blunt-body configurations have been studied. The flow patterns on these configurations were threedimensionally visualized through Schlieren images. It was observed that the usage of an aero-disk spike reduced the aerodynamic drag by 50%-60%. Additionally, peak surface heat flux reduced significantly. Similar drag reduction trends were noticed with the usage of the blunt tip version as well, but with further reduction in peak surface heat flux. In conclusion, the usage of blunt tip aero-disk spike on the configuration labeled 3221 has significantly improved the drag and surface heat flux effects.