Ducted Hydrokinetic Turbine Design Optimization Using CFD-based Adjoint Method

Hydrokinetic turbines are designed to extract energy from different natural water sources, such as rivers or tidal and ocean currents. In order to improve the efficiency of energy extraction, a duct can be used to accelerate and condition the fluid flow passing across the turbine. In this work, we explore optimal design of a ducted hydrokinetic turbine to maximize the hydrodynamic efficiency, which is believed to exceed the Betz' limit (the theoretical limit derived from a bare turbine). For this purpose, we perform optimization on both the blade and duct geometries simultaneously using the CFD-based discrete adjoint method, implemented in an open-source environment DAFoam. The results will be discussed in terms of the maximum efficiency achieved and the effect of duct to turbine performance.