Simulation of two in-line wind turbines using an incompressible Finite Volume solver coupled with a Blade Element Model

Abstract

The present study addresses the first steps of development and validation of a coupled Finite Volume-Blade Element Model (FV-BEM) simulation tool dedicated to offshore wind turbine farm modeling. The fluid domain is solved using the incompressible formulation of the CFD solver Grid-flow [40]. The turbines are taken into account using FAST (from NREL) [23] and their effects are imposed into the fluid domain through an actuator line model (ALM) for which specific enhancements are proposed. The Grid-flow solver and its two-way coupling with the aero-elastic modules from FAST are introduced and detailed. The present two-way coupling is built on a parallel framework using the MPI library. The ALM force coefficient values are deduced by FAST from the incident local velocity interpolated from the CFD solver grid at each timestep. In return, the ALM forces computed by FAST are projected from its cylindrical support to the Cartesian grid of the CFD solver. This force projection is made through a specific kernel interpolation technique inspired from meshless methods such as Smoothed Particle Hydrodynamics (SPH). The simulation of the case of two in-line wind turbines using the FV-BEM coupling proposed is presented, together with comparisons against experimental results for validation purposes. Coarse and refined grid results are compared and discussed. Finally, a discussion on performances, advantages and limitations of the formulation proposed is provided.