Three-dimensional numerical modeling of flow dynamics and investigation of temporal scour hole development around paired stream deflectors in a laboratory flume

A three-dimensional numerical model (PHOENICS) was used to investigate the role of stream deflector angle and length on the flow field in a rectangular laboratory flume. Subsequent bed topography surveys were performed to examine the role of obstruction angle on scour hole development over time. The model was capable of predicting laboratory velocity and turbulent kinetic energy measurements, performing better for flow over a flat stable bed than over a deformed sand bed. A new method of incorporating complex bed topography into a structured Cartesian mesh was developed in the process. Flow field properties such as dynamic pressure, velocity amplification, separation zone length and width, and downwelling extent and magnitude were found to be strongly dependent on deflector geometry. Equilibrium scour hole depths and geometry are also angle-dependent. A predictive equation was produced explaining the rate at which scour holes reach equilibrium, and compared well with existing literature. Finally, a method was developed whereby characteristics of the flow field over a flat, stable bed could be used to predict equilibrium scour hole geometry