Numerical Analysis of Reynolds Stresses for Developing Turbulent Flow in Square-Sectioned Bend.

Abstract

A numerical analysis has been performed on developing turbulent flow in a square-sectioned 180 deg bend. The ratio of bend mean radius of curvature to hydraulic diameter is 3.35, and straight ducts 31 hydraulic diameters long extend from the inlet and outlet planes of the bend. In calculation, an algebraic stress model was adopted in order to predict Reynolds stresses precisely, and a boundary-fitted coordinate system was introduced to briefly set boundary conditions. calculated results were compared with the experimental data available. Special attention is paid to the distributions of Reynolds stresses in the square-sectioned duct and bend. The present method can predict well the measured sharp spike in streamwise velocity fluctuations near symmetry at 90 deg. Contrary to this agreement, rapid decrease of the radial velocity fluctuations at the same location in the experimental results is not predicted well by the present method. Although there are a few discrepancies, calculated results are in good agreement with the experimental data. Judging from these comparisons it is confirmed that the present method including the turbulent model is applicable for this complicated flow.