The advances in aerospace engineering allow modern-day aerial vehicles to reach hypersonic speeds. Apart from rocket propulsion, supersonic combustion ramjet (or scramjet) technology is popularly utilized for this purpose. This is because, unlike rockets, scramjets are air-breathing engines and do not need to carry the oxidizer with them during flight. A scramjet engine also has a high thrust to weight ratio. The hypersonic CFD group carries out extensive research on scramjets, which is mostly in collaboration with and/or funded by the national space and defence labs.

There are several areas of research in scramjet technology, such as intake design, supersonic combustion, boundary layer control etc. Among these, design and simulation of scramjet intake is one of the most important. This is because unlike other air-breathing engines, scramjets do not have compressors or turbines as components. The engine operates on Brayton cycle and the compression of flow is achieved through shock waves in the intake. Therefore, a scramjet engine resembles a duct in which shock waves occur at specific locations and compress the flow. Heat addition in the combustion chamber and flow expansion in the nozzle lead to a net positive thrust at high speeds. This is not possible for other air-breathing engines, where the weight and drag added by heavy machinery does not allow a net positive thrust to be produced at hypersonic speeds.

The objective of intake design is to enable maximum static pressure rise and mass flow rate through the shock waves, while ensuring minimum total pressure loss. Analytical relations, based on gas dynamics, are utilized for this purpose. Several intake geometries and configurations, designed with these analytical relations, have been studied by the group. Detailed CFD simulatons of model scramjet intakes as well as realistic geometries are carried out to study the shock pattern. High fidelity simulations to capture shock-shock and shock-boundary layer interactions are used. In addition, three-dimensional simulations are performed to capture side wall effects and the shock waves generated by side fences.