3D Prediction of Developing Turbulent Flow in a 90° Duct of Rectangular Cross-Section

Abstract

Turbulent flow in curved ducts occurs in many engineering applications such as centrifugal pumps, aircraft intake and in the cooling passages of gas turbine blades. An important characteristic which distinguishes such flows from those in straight ducts is the generation of strong secondary motions. In this work, a numerical investigation has been undertaken to study incompressible, developing turbulent flow through a 90° duct of rectangular cross-section [1]. The main objective has been to assess the effectiveness of the Launder and Sharma [2] low-Re k − e model and the nonlinear low-Re k − e model of Craft et al. [3] in predicting turbulent flow in curved ducts. In this study, the governing equations of mean flow are solved using an extended version of STREAM-3D [4] finite volume code. The pressure field is obtained using the SIMPLE algorithm and the convection terms in all transport equations are approximated using the QUICK scheme. The predicted velocity vectors, in Figure 1(a), indicates that the duct curvature causes flow acceleration and deceleration along the convex surface, and reverse along the concave surface. Furthermore, Figure 1(b) shows that the curvature induces a strong secondary motion which as a result of that the core fluid displaces towards the convex surface.