Numerical study of anisotropic turbulence in entrance-blocked narrow rectangular channel

Abstract

Numerical study of turbulent flow in a narrow rectangular channel with side entrance blockage ratio from 0.25 to 0.9 was conducted under Reynolds numbers (Re) from 2,180 to 100,900. The Pearson similarity criterion was evaluated for mesh size sensitivity and turbulent models based on experimental data. Based on the validated turbulent model, predicted turbulent flow was studied.The entrance blocked channel forms jet-flow at inlet, shear-flow layer and recirculation vortex downstream of the blockage, with high Reynolds stress in the shear-flow layer. Then the streamwise flow reattaches the side channel wall. With blockage ratio increasing, the time-averaged velocity and Reynolds stress increase. With Re increasing, the time-averaged velocity and Reynolds stress decrease. The reattachment length increases in exponential law with blockage ratio and in power function with Re.The strong anisotropic turbulent flow in entrance-blocked narrow rectangular channel was evaluated by the Lumley triangle. In the streamwise plane, the anisotropic states in the recirculation vortex spread in the Lumley triangle, and they are two-dimensional wall turbulence in shear-flow layer and streamwise flow. Generally, the anisotropic states are dominated by two-dimensional wall turbulence and show tendency toward isotropic turbulence with Re increasing. The anisotropic states become towards isotropic in the recirculation vortex, stable in two-dimensional wall turbulence in shear-flow layer and one-dimensional turbulence in streamwise flow with blockage ratio increasing. These findings improve understandings of turbulent flow in the entrance blocked narrow channel.