Turbulent flow around submerged foundation arrays for ocean energy

Abstract

Submerged ocean energy foundations experience dynamic loading due to the non-uniform approach velocity and wake propagation behind them. This paper investigates the unsteady turbulent flow dynamics and propagation of large-scale vortical structures around submerged foundations using a large eddy simulation. The computational domain constituted an array of eight foundations arranged in an inline configuration of two columns. Two streamwise spacing, x = 6D and 8D, are investigated at an approach Reynolds number, based on the channel hydraulic diameter, of 8.5 × 104. The parametric study reveals the expected changes in wake recovery and their impact on the downstream foundations. The narrow spacing promotes intense wake interactions, while larger inline spacing causes the entrainment of ambient flow, thereby limiting the wake interaction with the downstream foundations. A two-point correlation analysis reveals larger integral turbulent timescales for the 6D spacing compared to the 8D spacing. The separated flow around the foundations is characterized by eddies shed at varying frequencies. Multiple spectra peaks dominate at low frequencies, signifying dominant energy-containing large-scale vortices coupled with periodic excitation of the vortices as energy is transferred from the large-to small-scale turbulent structures.