Determination of establishment length in open channels using 3D numericalmodeling

摘要

A dimensionless length is suggested for predicting the length of the flow developing zone of open channel flow. This region is downstream of a distance which is beyond the flow field's behavior is invariant. The developing region in open channel is a complex three-dimensional flow area that influenced by secondary current and free surface effects, and is therefore not amenable to analytical solutions. This study is based on numerical technique of flow in open channels. The numerical procedure is using ANSYS-CFX software package for solving 3D Navier-Stokes equations and computing velocity distributions over a cross-section. By using the numerical code, we study the effects of different terms on the establishment length. A simple empirical formula was obtained from which it is possible to predict the length of the entry region.