Numerical Analysis of a Scramjet Inlet using OpenFOAM

The conceptualization of hypersonic air-breathing technology is very important which will eventually lead to the design and development of hypersonic air-breathing missiles for defense applications. A typical Scramjet engine (supersonic combustion ramjet) operates in the high Mach number regime where complex phenomena including shock-shock / shock-boundary layer interactions take place. Moreover, looking at the Scramjet inlet (air-intake system), the following design constraints need to be taken care of for adequate generation of thrust: • The static pressure at the exit of intake section must be greater than 50000 N/m2 from the point of view of Scramjet combustion. • The Mach number at the intake exit must be around 2. • The static temperature at the entry of the combustor must be greater than 1000 K for ignition. In addition to this, the leading edge nose bluntness plays a pivotal role in mass capture, total pressure recovery and wall heat flux. Side fencing for a typical inlet enhances mass capture but also increases the viscous drag. Experimental analysis of such a complex 3-D scenario becomes difficult as well as costly, and hence numerical methods is the practical solution to analyze such cases. In the current work, OpenFOAM, which is an open source CFD tool, is used to simulate a 3-D Scramjet inlet, which solves the Reynolds averaged Navier-Stokes equations coupled with k-omega SST turbulence model. Parametric study has been performed by varying the leading edge nose radius and angle of attack to achieve optimum mass flow rate and wall heat flux. rarefiedHypersonicFoam [11], which is an in-house solver at IIT Hyderabad developed by Gijare et al. has been used to predict flow properties in the hypersonic flow regime, as applicable to the Scramjet inlet case. The solver uses rhoCentralFoam (based on the central upwind schemes by Kurganov [12]) as its base solver and has been modified to compute transport properties of multi- vi species mixture based on kinetic theory. Initially, the solver is validated against experimental data for various test cases in the higher Mach number regime