CFD-based design optimization of a 5 kW ducted hydrokinetic turbine with practical constraints

TL;DR

This paper presents a CFD-based optimization framework for designing a ducted hydrokinetic turbine that maximizes efficiency while satisfying practical manufacturing constraints, resulting in a more efficient design than traditional turbines.

Contribution

It introduces a combined CFD, adjoint, and gradient-based optimization approach for complex ducted turbine geometries with practical constraints.

Findings

Optimized ducted turbine achieves up to 50% efficiency.

Outperforms traditional freestream turbines with similar hub.

Design features a short, thin duct with a rounded leading edge.

Abstract

Ducted hydrokinetic turbines enhance energy-harvesting efficiency by better conditioning the flow to the blades, which may yield higher power output than conventional freestream turbines for the same reference area. In this work, we present a ducted hydrokinetic turbine design obtained by simultaneously optimizing the duct, blade, and hub geometries. Our optimization framework combines a CFD solver, an adjoint solver, and a gradient-based optimizer to efficiently explore a large design space, together with a feature-based parameterization method to handle the complex geometry. Practical geometrical constraints ensure the manufacturability of the duct in terms of a minimum thickness and the housing of a 5 kW generator within the hub. The optimization converges to a short, thin duct with a rounded leading edge and an elongated hub protruding the duct inlet. The optimized ducted turbine achieves up to 50% efficiency when evaluated by RANS/URANS solvers despite a bulky hub, outperforming the 45% efficiency of the freestream Bahaj turbine featuring the same hub. This work showcases the effectiveness of CFD-based optimization in advancing ducted turbine designs and demonstrates the hydrodynamic benefits of a ducted configuration, paving the way for future research and real-world applications.