Large eddy simulation of a utility-scale horizontal axis turbine with woody debris accumulation under live bed conditions

Abstract

Tidal and riverine flows are viable energy sources for consistent energy production. Installing and operating marine hydrokinetic (MHK) turbines requires assessing any potential impact of debris accumulation on turbine performance and sediment transport. More specifically, MHK devices may alter the natural sediment transport processes and cause debris accumulation, disrupting the natural sediment dynamic. In turn, these processes could affect the turbine’s performance. We carried out a series of large-eddy simulations coupled with bed morphodynamics, introducing various debris loads lodged on the upstream face of a utility-scale turbine tower. The objective is to systematically investigate the impact of debris accumulation on the performance and hydro- and morpho-dynamics interactions of the horizontal-axis MHK turbine under rigid and live bed conditions. To that end, we (1) employed the actuator line and surface methods for modeling turbine blades and the nacelle, respectively, (2) directly resolved individual logs, and (3) solved the Exner equation to obtain the instantaneous bed deformation of the live bed. Our analysis revealed that while the spinning rotor amplifies scour around the pile, debris accumulation modifies the sediment dynamics of the system. Also, it found that morphodynamic processes accelerate the wake recovery, slightly enhancing the turbine’s performance.