A comparison study between CFD analysis and PIV technique for velocity distribution over the Standard Ogee crested spillways

Abstract

A comprehensive study was performed to compare flow rate, mean velocity, vertical velocity distribution, and locations where the maximum velocity, dm, occurs on standard Ogee-crested spillways using experimental and numerical models. Five different models were constructed from rigid foam according to the specifications of the United States Army Corps of Engineers (USACE). The velocity of the flow was recorded along the downstream curve of the model for all models with different non-dimensional head ratios H/Hd of 0.50, 1.00, and 1.33. Particle Image Velocimetry (PIV) was used to measure the flow velocities. Velocity distributions were obtained by analyzing a series of captured images using Matlab codes. A commercially available Computational Fluid Dynamics (CFD) software package, Flow-3D, was used for modelling the experimental model setups. Flow-3D analyzes the Reynolds-averaged Navier-Stokes equations and is widely verified for use in the field of spillway flow analysis. The maximum difference between numerical and experimental results in mean velocity values that do not exceed 6.2% for all values of head ratios. The interpolated values of recorded maximum velocity by the PIV technique are smaller than those values numerically computed. In the lower dm locations, the percent difference between these regions reaches -8.65%; the upper locations are 2.87%. The vertical location (dm) drops to the lower location when the upstream head increases, and the distance from the spillway axis decreases linearly.