Author(s)

MONSIF SHINNEEB, GHASSAN NASIF, RAM BALACHANDAR

Abstract

This study investigates numerically the effect of the aspect ratio (AR) on the velocity field characteristics of the turbulent flow of a straight open channel flow. The AR is defined as the ratio of the width of the channel in a plane normal to the flow direction, to the flow depth. In this study, two aspect ratio cases are investigated; a narrow case of AR = 1 and a wide case of AR = 12. The transient three-dimensional Navier–Stokes equations were numerically solved using a finite-volume approach with detached-eddy simulation (DES) turbulence model. The free surface was simulated using flatwave model linked with the volume of fluid method. The objective of this study is to enhance our understanding of the effect of the AR on the formation of secondary currents in a channel flow. The results revealed the formation of a pair of counter-rotating recirculation zones near the bottom corners of the channel, whose axes are aligned with the main flow direction. The AR appears to significantly influence the size and strength of the recirculation zone that resides near the sidewalls. The distribution of the turbulent kinetic energy of the flow appears quantitatively similar for both the AR cases; however, the magnitude appears to increase with decreasing the AR.

Keywords

secondary currents, turbulence, DES model