Wave Generation in Open Channels by Vortex Shedding from Channel Obstructions

Abstract

Transverse surface waves were produced in a rectangular open channel in the region where the otherwise steady, uniform, flow passed through a cluster of vertical circular cylinders. The cylinders could represent either naturally occurring obstacles such as vegetation or man-made structures such as a group of piles driven into the bed of a river. The waves were produced from the periodic forces created by the vortex shedding from the cylinders. These forces generated and then amplified transverse waves in the channel. In some experiments the waves had amplitudes of 35% of the mean flow depth. These resonance-generated waves produce a seiching that can occur in hydraulic models as well as prototype systems. Both laboratory experiments and a theory-based analysis were used to determine the relationship between the amplitude of the vortex-generated wave, average velocity of the approach flow, viscosity of the fluid, width of the rectangular channel, depth of flow, cylinder diameter, and cylinder placement configuration.