The stepback technique is a method for exactly computing flows which are truly conical. We show that it can be an effective approximate method for nearly conical flows such as viscous flow past cones. When used this way, the technique effectively employs a conical approximation of fully three-dimensional flows. In this talk, the accuracy of the stepback technique is studied for hypersonic viscous flows past cones. Both frozen and equilibrium dissociating flow, using the Ideal Dissociating Gas model, are considered. The numerical finite-volume method employed is the kinetic- based Equilibrium Flux Method (EFM) and its successor, EFMO.
The accuracy of the stepback technique was tested on a variety of flows. When applied to hypersonic boundary layers on cones at zero yaw, both reacting and frozen, it was found that the stepback method underestimates the thickness of boundary layers. Another simulation of a frozen cone at a high angle of attack is compared with previous experimental results in terms of surface conditions and flow features (shock locations, separation point, etc.)
A strategy is presented which combines the stepback method with conventional time-marching methods to achieve high-accuracy solutions in much lower computational time than fully three-dimensional solutions. These solutions are compared with pure stepback solutions and previous experiments for the case of a reacting cone at high angle of attack. The effects of Reynolds number and dissociation on flow features such as the bow shock standoff distance and the leeward vortex position are examined.Back to Fluid Mechanics Seminar Page