Unsteady Numerical Simulations of Turbulence and Coherent Structures in Axial Flow Near a Narrow Gap

Abstract Axial flow in a rectangular channel containing a cylindrical rod has been simulated numerically by solving the unsteady Reynolds-averaged Navier–Stokes equations with a Reynolds stress model. The time- and phase-averaged mean velocity and turbulent stresses are in fair agreement with previous experimental results in a similar configuration. The study further documents the formation of quasi-periodic coherent structures in the form of vortex pairs and the important role that they play in transporting fluid across the gap region.