Experimental Study on Flow Partitioning Based on Turbulence Shear Stress

Most river engineers believe that a river flow can be divided into three parts by division lines. The hypothesis is receiving much attention, and many believe it is only a mathematical treatment to simplify the complex flows and has no physical basis. Those who believe the existence of division lines also argue whether the division line should be linear or curves. Even the argument is intensive, no specially designed experiments were conducted to verify which statement is true, and which model is reliable to predict the real division lines, not to mention whether the existence of division lines can be inferred from its turbulence shear stress. The aim of this paper is to show the existence of division lines by analyzing the turbulence shear stress in duct and channel flow. The division line theories of Keulegan[1], Daido[2], Yang and Lim[3] and Guo and Julien [4] were selected for comparison in this study which yielded varying results with the experimentally observed division line. The physical existence of division lines is illustrated in this study of flows through smooth ducts and channels, and the concept that the flow region can be partitioned is validated.