Numerical simulation of turbulent flow in a channel containing a small slot

Abstract

A three-dimensional unsteady simulation was carried out to predict the main features of the turbulent flow inside a closed channel connected to a lateral slot. The incompressible turbulent flow was modelled using a hybrid Detached Eddy Simulation (DES), that uses an LES/URANS approach to predict the turbulence. The calculations were performed using ANSYS® CFX. In this work the main channel has a size of 180 mm x 136.20 mm. The small subchannel is characterized by its deepness, p = 77 mm and width, d = 10 mm. The Reynolds number, based on the hydraulic-diameter, Dh, the bulk velocity, and the kinematic viscosity, ν, in the main channel was Re = 2.25 × 105. Inside the small slot the velocity distribution was found to depart from the law of the wall and the normal Reynolds stresses, u′u′¯ and v′v′¯, were found to dominate the mixing process. Velocity time-traces extracted at locations as far as y/p = 1.125 inside the gap evidenced the presence of large eddies travelling inside the small channel. It was shown that periodic streamwise boundary conditions can be applied to this problem, and good results were obtained by using a channel length that was approximately twice the wavelength of the experimentally observed coherent structures. The results were found to be in fair agreement with the results presented in Meyer and Rehme (1994), though a certain lack of information on turbulence in single channels connected to a gap still remains.