Design of an optimized porous disk to match wake properties of a floating wind turbine

Abstract

Experimental studies of floating offshore wind farms are constrained by scaling limitations that make the use of bladed rotors impractical at the wind farm scale. Porous disks mounted on moving platforms therefore represent a viable alternative, provided that their design reliably reproduces turbine wake characteristics. This work proposes a rational design methodology for porous disks based on a Darcy–Forchheimer porous media formulation within a computational fluid dynamics framework, in which resistance coefficients are directly linked to the disk solidity distribution. Three disk designs with different radial solidity distributions, all matching the thrust coefficient of a reference three-bladed rotor, are investigated under static and imposed-motion conditions. The results show that the solidity distribution mainly affects the near- and mid-wake structure, while its influence diminishes downstream. A non-uniform solidity distribution based on blade loading provides the closest agreement with experimental wake data. Under imposed motions, the optimized disk captures very well the mean wake deficit, with a slightly slower recovery than the bladed rotor limited to the surge case. The proposed methodology provides practical guidance for the physical realization of porous disks in floating wind farm experiments.