Zonal Immersed Boundary Conditions: Application to a High-Reynolds-Number Afterbody Flow

Abstract

The present paper focuses on a new numerical strategy consisting of the zonal use of the immersed boundary conditions combined with the ability of zonal detached-eddy simulation to simulate high-Reynolds-number separated flows. The validation test case is a simplified space launcher afterbody with a control device in the form of a short cylindrical serrated skirt. “Zonal immersed boundary conditions” are used to handle the introduction of the skirt into the preexisting structured curvilinear grid that describes the noncontrolled configuration. The governing equations are solved using a standard body-fitted finite volume technique over the whole grid. A direct forcing source term is added when cells are internal to the skirt (that is, solid) to drive the velocity and the turbulence variables to the chosen values. Numerical simulations are performed at a Reynolds number of and a freestream Mach number of 0.702. The numerical results demonstrate the ability of the zonal immersed boundary conditions to successfully impose the desired values at solid nodes. The first- and second-order moments, as well as the fluctuating pressure field, illustrate a fairly good agreement between the experiment and the numerical simulation. It is shown that the serrated skirt acts as a smooth device, which does not affect the global dynamics of the flow and only delays the location of the separation. Finally, the zonal immersed boundary conditions appear to successfully reproduce the effect of the skirt while drastically reducing the time of the grid generation.