Prediction of Turbulent Separated Flow in a Turnaround Duct Using Wall Functions and Adaptivity

Abstract

This paper presents an application of adaptive remeshing to the prediction of turbulent separated flows. The paper shows that the κ - ϵ model with wall functions can predict separated flows along smooth curved surfaces. Success is achieved if the wall functions exhibit values of y+ close to 30, and if meshes are fine enough to guarantee that wall function boundary conditions are grid converged. Adaptive remeshing proves to be a very cost effective tool in this context. The methodology is demonstrated on a problem possessing a closed form solution to establish the performance and reliability of the proposed approach. The method is then applied to prediction of turbulent flow in an annular, axisymmetric turnaround duct (TAD). Predictions from two computational models of the TAD are compared with experimental measurements. The importance of appropriate meshes to achieve grid independent solutions is demonstrated in both cases. Better agreement with measurements is obtained when partially developed profiles of u, κ, and ϵ are specified at the TAD inlet.