Dynamics of Open-Channel Flows Over Inclined Planar Obstacles

High-resolution PIV laboratory measurements were made of the velocity field created by open-channel flows interacting with inclined planar obstacles. Eleven different inclination angles, ranging from 25^° to 90^° , were investigated. An Eulerian control volume analysis was then conducted to understand the effect of the inclination angle (θ) on how energy is dissipated over the obstacle. Results show that as θ decreases, the relative kinetic energy dissipation rate (ϵ) decreases in a non-linear but monotonic fashion. The main energy sink is identified as a recirculation eddy that is present at higher θ, but then becomes unstable and eventually diminishes as θ decreases. The dimensions of this eddy are used to describe the structure of the flow field upstream of the obstacle. The effect of the upstream inertial condition (Re) on ϵ for a fixed θ was also investigated. It was found that ϵ decreases with increasing Re in a fixed range, but below a threshold Re of ∼ 3 × 10⁴ , ϵ increases significantly due to the growing influence of viscous effects. The practical implication of this research on the development and proper use of hydraulic structures that offer both accurate flow measurement and efficient upstream stage control is discussed.