Predictive wind turbine simulation with an adaptive lattice Boltzmann method for moving boundaries

Ralf Deiterding,Stephen L Wood

doi:10.1088/1742-6596/753/8/082005

Abstract

Operating horizontal axis wind turbines create large-scale turbulent wake structures that affect the power output of downwind turbines considerably. The computational prediction of this phenomenon is challenging as efficient low dissipation schemes are necessary that represent the vorticity production by the moving structures accurately and that are able to transport wakes without significant artificial decay over distances of several rotor diameters. We have developed a parallel adaptive lattice Boltzmann method for large eddy simulation of turbulent weakly compressible flows with embedded moving structures that considers these requirements rather naturally and enables first principle simulations of wake-turbine interaction phenomena at reasonable computational costs. The paper describes the employed computational techniques and presents validation simulations for the Mexnext benchmark experiments as well as simulations of the wake propagation in the Scaled Wind Farm Technology (SWIFT) array consisting of three Vestas V27 turbines in triangular arrangement.

Highlights

The majority of available computational fluid dynamics (CFD) methods for wind engineering approximate the incompressible or weakly compressible Navier-Stokes equations, which leads to a globally coupled problem that in practice can only be solved by iteration
Simulations of turbines that resolve structural and topographic details accurately to the cm scale have concentrated on simulations of the NREL Phase VI [3] and the Mexnext benchmark experiments [4], in which large-scale laboratory rotors are operated at prescribed rate of rotation in quasi-uniform inflow
By discretizing the particle velocity space on an equidistant Cartesian grid and employing a time-explicit streaming and collision algorithm [8], in which transport of quantities is always exactly by one grid point, the lattice Boltzmann method (LBM) exhibits the properties of a low dissipation scheme for weakly compressible flows, while computing times are considerably reduced compared to typical Navier-Stokes-based CFD solvers [9]

Summary

Introduction

The majority of available computational fluid dynamics (CFD) methods for wind engineering approximate the incompressible or weakly compressible Navier-Stokes equations, which leads to a globally coupled problem that in practice can only be solved by iteration. This is in good agreement with a documented result from the structured Wind Multi-Block code by Liverpool University that required 7128 h CPU with a grid of ∼ 34 M cells to compute one revolution of the Mexnext three-bladed rotor, which corresponds to an effort of 209 h CPU/1M cells/revolution [4].

Results

Conclusion