Combining ZDES with Immersed Boundary Conditions Technique for the Treatment of Complex Geometries

Abstract

The present paper focuses on a numerical strategy called ZIBC consisting of the zonal use of Immersed Boundary Conditions combined with the ability of Zonal Detached Eddy Simulation (ZDES) to simulate high Reynolds number separated flows. The motivation of such a strategy lies in the accurate handling of geometrically complex configurations with validated unsteady tools. A first assessement of the strategy has already been performed by evaluating the introduction of a control device in a form of a short cylindrical serrated skirt into a simplified space launcher afterbody. To go further into validation, this paper focuses on the ability of the ZIBC strategy to reproduce the fluctuating pressure field. The test case corresponds to a simplified space launcher afterbody and consists of a cylinder elongated by another cylinder of smaller diameter (i.e. an extension). Immersed Boundary Conditions are used to handle the introduction of the extension into a structured curvilinear grid fitting the ZDES requirements to treat the blunt body 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, i.e. solid, to drive the velocity and the turbulence variables to the chosen values. Numerical simulations are performed at a Reynolds number of $1.2\times 10^{6}$ and a free stream 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 illustrate an excellent agreement between the experiment and the numerical simulation. Finally, the “Zonal Immersed Boundary Conditions” appear to successfully reproduce the effect of the extension.