Three-dimensional calculation of turbulent duct flow with non-uniform inlet conditions

Abstract

Three-dimensional calculations are reported of developing flow in a square duct with non-uniform inlet conditions. The non-uniformity was generated at the entrance of each of four subducts formed by placing a cruciform into developed flow in a larger square duct. A foward-marching, finite difference procedure is used to solve numerically the flow equations, and the turbulent stresses are calculated with an algebraic stress model derived by simplifying model transport equations for the individual stresses. This model, in contrast to isotropic eddy viscosity expressions, allows the simulation of turbulence-driven secondary flows in non-circular ducts. The calculated development of the mean flow and turbulence quantities is generally in good agreement with experimental data. A detailed study of the redevelopment of the secondary motion from the corner flow prevailing in the large duct to the corner flows in the subduct is presented. A genuine feature of the calculations is that they are true predictions as the experimental data became available only after the calculations had been completed.