Large-Eddy Simulation of Turbulent Flow in a Channel with Streamwise Periodic Constrictions

We present results from wall-resolved and wall-modeled large-eddy simulations of turbulent flows in a channel with streamwise periodic constrictions on the bottom. Two cases: (1) $Re_h=10600$, ERCOFTAC test case 81 and (2) $Re_h=33000$, periodic hill experiment reported by Kahler et al. (J. of Fluid Mech., 2016) are utilized to validate our wall-resolved and wall-modeled LES results. The stretched spiral vortex sub-grid scale (SGS) model is used to compute the SGS term, and the ``virtual'' wall model, originally developed by Chung & Pullin (J. of Fluid Mech., 2009), is extended to generalized curvilinear coordinates. The wall model dynamically couples the SGS stress from the outer region and offers boundary conditions at a raised ``virtual'' wall for the LES region. The numerical results show that the wall model is able to accurately predict mean flow characteristics, including the location of the separation bubbles. Moreover, the skin friction and near-wall streamlines are presented to quantify the separation and reattachment in the near-wall region. The anisotropy of the Reynolds stress tensor are also evaluated, potentially providing some guidance to the RANS modeling community.