Transient flows past arrays of yawed finite prisms

Abstract

Transient flows past arrays of yawed finite-length prisms in tandem and staggered arrangements are simulated. Large eddy simulation method is employed to characterize spatial and temporal characteristics of flows in the vicinity of prisms. Drag coefficients of prisms are determined for different spacing and yaw angle of prisms. Three-dimensional effects are investigated for different spacings of prisms in a tandem array. Drag coefficient of downstream prism is significantly lower compared to that of upstream prism when prisms are tightly spaced. Drag coefficient of downstream prism predicted by simulations in three-dimensional geometry is recovered fully as spacing approaches 10 times the height of the prism while drag coefficient predicted by simulations in two-dimensional geometry is only about 30% of the upstream prism even when two prisms are separated by 20 times the height of the prism. The wake flow patterns do not influence the drag coefficient strongly for the staggered arrays of yawed prisms. Prisms can be placed in a tighter arrangement without a significant penalty of drag reduction. Mathematical models and numerical methods employed are validated by comparing simulation results against experimental results. Drag exerted on these prisms can directly be related to power generation by devices containing translating blades of marine-current applications. This study demonstrates that arrangement, spacing, and yaw angle can be used to design and optimize energy harvesting devices and other offshore structures.