Transverse Velocity, Transverse Boundary Shear Stress and Flow Deviation in Meandering Open Channels   

Abstract

This study presents a novel approach for characterizing the mechanics of flow in mildly meandering open channels, specifically focusing on the development of a new vertical distribution equation for transverse velocity. Unlike existing equations in the literature that rely on complex logarithmic or integral forms or infinite series forms, which are impractical for hydraulic engineers, the proposed equation employs ordinary power functions. This new formulation offers several advantages, including the consideration of previously neglected lateral forces resulting from wind and ship movement. Comparisons with available existing equations indicate a good agreement, highlighting the accuracy, sensitivity to roughness, and applicability of the developed transverse velocity equation. Notably, the analysis reveals that wind velocities can significantly increase transverse surface and bed velocities, emphasizing the importance of considering such factors in flow characterization. Moreover, the present approach yields higher transverse surface and bed velocities compared to a well-known existing equation. The equation for transverse velocity relies on two key assumptions. Firstly, it assumes a constant turbulent viscosity throughout the flow. Secondly, it relies on the condition that the topographic steering number is less than one, allowing for the approximation of mild curvature and meandering conditions. In addition, the developed transverse velocity equation is the only equation that offers derivation for an expression for the transverse boundary shear stress. This expression accounts for the effects of the centripetal force and the transverse pressure force, providing a comprehensive understanding of the flow dynamics in meandering channels. The study further presents distinct expressions for the deviation angles of the flow velocity and the bed shear stress, enhancing our understanding of the complex mechanisms governing flow behavior in meandering channels.