Numerical Analysis of Turbulent Flow Developing in a 30/60 Degree Right Triangular Duct.

Abstract

Numerical data are reported for turbulent flow developing in a right traiangular duct with internal angles of 60 and 30 deg. An overwhelming number of numerical and experimental studies on noncircular ducts have dealt with ducts that contain one or more symmetry planes. In contrast, this duct has no symmetry planes. In the calculation, an algebraic Reynolds stress model was adopted in order to predict anisotropic turbulence precisely, and a boundary fitted coordinate system was introduced as the method of coordinate transformation. Calculated results were compared with experimental data measured by a hot-wire anemomenter. As a result of the comparison of the two results, it was found that the present method could reproduce the characteristic features of streamwise mean velocity and Reynolds stresses. The present method also predicted secondary flow of the second kind which was generated by anisotropic turbulence, whereas the experimental analysis failed to show the distribution of the secondary flow as a result of scattered data. By evaluating the production terms of streamwise normal stress, it was clarified that the distorted contours of streamwise normal stress toward the corner were generated not by secondary flow of the second kind but by production terms of its normal stress. Although it is said in general that distorted contours are responsible for Reynolds-stress-driven secondary flow, this is not true in the case of streamwise normal stress.