Simulation of turbulent flow in contracting and expanding ducts with a linear k-ε model

Abstract

This work presents numerical predictions for turbulent flow field confined in a circular duct past a gradually varying cross section segment. Both expanding and contracting sections were investigated. Equations of boundary-layer type were used and the standard linear k-ε model was applied. A forward marching method was employed for sweeping the computational domain. Results are presented for contractions and diffusers in addition to comparisons with experimental data for air. Turbulence damping in contractions and its enhancement in diffusers were correctly calculated. Further, for contractions with angles of up to 21° degrees, the use of a parabolic solver showed good agreement with experimental values for the mean and statistical quantities. For diffusers, adverse pressure gradient along the flow limits the quality of the predictions as the angle and length of diffuser increase past 5° and 10 duct radius, respectively.