Shock wave boundary layer interaction (SBLI) & Inlet Design for Air breathing propulsion

SBLI flows are inherently seen in the transonic, supersonic or hypersonic flow regimes, where the shocks originate & impinge on the boundary layer developing on any part an aircraft or an aircraft engine. In supersonic/hypersonic flows, SBLI becomes one of the most important features that need to be predicted & analyzed because of its detrimental effects to the performance of key parts like the inlet of the engine, control surfaces of the wing/tail & so on. The work that I am currently doing, involves analyzing & predicting the key aspects of the major effects of three dimensional SBLI being – separation bubble formation leading to inlet unstart & high heat transfer rates.

Starting from the two-dimensional practical scramjet inlet, we analyze the key features of SBLI like the separation bubble size, heat transfer rates at the point of separation & re-attachment. It was found in the 2D flow analysis that, the shockshock interactions from the cowl tip & the isolator of the scramjet inlet are the main features that need to be looked into carefully while designing an inlet.

Then using some three-dimensional canonical (simple) geometry, various flow features like shock-shock interactions, conical vortices, side-wall effects (3D effect, not seen in 2D) lead to a spanwise variation of separation bubble structure was also observed & analyzed. A complex secondary zone was found downstream in the isolator, which was analyzed using the standard topological structure as mentioned by Tobak & Peake22.

We use a 3D RANS in-house code for modeling & simulations. The turbulence closure is accounted for by using the one equation Spallart-Alamaras4 (SA) model. An implicit scheme13 with 2nd order accurate in space & 4th order accurate in time is used.

RANS Modeling

It has been found that the existing turbulence models with compressibility corrections, either over-predict/under-predict the turbulent heat flux term in the energy equation of RANS equations. Thereby, one way to accurately predict the turbulent heat flux term of the energy equation is by using algebraic models which has been shown by Bowersox1. Efforts are being taken to apply this model stated by bowersox into our in-house to predict accurate results for a simple geometry. Once done, the model is planned to be implemented in predicting accurate turbulent heat flux term for more complex cases, thereby correct heat flux can be measured through CFD.

• M.Tech, Dept of Aerospace Engg., IIT Bombay, 2010-12
• B.E., Dept of Aeronautical Engg., Park College of Engg. & Technology- Coimbatore, affliated to Anna University – Chennai, 2006-10

"Extension of equilibrium turbulent heat flux models to high speed shear flows" by "Rodney.D.W.Bowersox", J.Fluid Mechanics, vol 633, pp 61-70, 2009.