A Parallel CFD Model for Wind Farms

Abstract

We present a Computational Fluid Dynamics (CFD) modeling strategy for onshore wind farms aimed at predicting and opti- mizing the production of farms using a CFD model that includes meteorological data assimilation, complex terrain and wind turbine effects. The model involves the solution of the Reynolds-Averaged Navier-Stokes (RANS) equations together with a k-ɛ turbulence model specially designed for the Atmospheric Boundary Layer (ABL). The model involves automatic meshing and generation of boundary conditions with atmospheric boundary layer shape for the entering wind flow. As the integration of the model up to the ground surface is still not viable for complex terrains, a specific law of the wall including roughness effects is implemented. The wake effects and the aerodynamic behavior of the wind turbines are described using the actuator disk model, upon which a volumetric force is included in the momentum equations. The placement of the wind turbines and a mesh refinement for the near wakes is done by means of a Chimera method. The model is implemented in Alya, a High Performance Computing (HPC) multi physics parallel solver based on finite elements and developed at Barcelona Supercomputing Center.The research of G. Houzeaux is being partly done under a I3 contract with the Spanish Ministerio de Ciencia e Inovación. The work of B. Eguzkitza is financed by a scholarship from the Fundación IBERDROLA supporting\ud the project ”Optimization of wind farms using computational fluid dynamics”.Peer ReviewedPostprint (published version

Domain Decomposition Methods for Domain Composition Purpose: Chimera, Overset, Gluing and Sliding Mesh Methods

“…The real topography was considered, using experimental wind measures as boundary conditions and the actuator disk theory to model the effect of the wind turbines. The actuator disk model [3] consists in introducing a sink in the momentum equations to extract volumetric momentum from the Navier-Stokes equations. We will now use this problem to test the hybrid conforming method.…”

“…For the continuous variational forms, both the extension-based and Dirichlet/Neumann formulations, respectively given by Systems (4) and (5), are equivalent to the one-domain formulation (3). At the discrete level, we only have equivalence for the discrete counterpart of the extension-based formulation.…”

An example of enhanced tephra deposition driven by topographically induced atmospheric turbulence

“…In order to test whether the topography around Yate could generate lee waves with dimensions that are compatible with our hypothesis, we have performed numerical simulations using the ALYA code, following a method developed by Avila et al (2013). We do not aim to replicate atmospheric conditions during the Cha1 eruption or to simulate tephra transport but to simply obtain an insight of how the topography around Yate influences lower atmospheric movements under plausible meteorological conditions.…”

High-resolution modelling of atmospheric dispersion of dense gas using TWODEE-2.1: application to the 1986 Lake Nyos limnic eruption

“…Houzeaux et al, 2009;Vázquez et al, 2016) is a high performance computing (HPC) multi-physics parallel solver based on a finite element method able to run with thousands of processors with an optimal scalability. Within this multi-physics general framework, Avila et al (2013) implemented a solver for the atmospheric boundary layer based on the RANS equations and a κ − turbulence model adapted to atmospheric flows in complex terrains. This model, called ALYA-CFDWind, can handle thermal coupling assuming the Boussinesq approximation although here we constrain to neutral atmospheric stability for simplicity.…”

“…4. The methodology uses the concept of transfer functions to couple the mesoscale Weather Research and Forecasting (WRF) (Skamarock et al, 2008) model with the CFD code Alya (Houzeaux et al, 2009) adapted to atmospheric boundary layer flows (Avila et al, 2013). Section 5 shows the TWODEE-2.1 model results for the 1986 Lake Nyos case of study and discusses how and why the model new features increase the accuracy of simulations.…”