Simulations of wind turbine wakes in realistic atmospheric conditions: from large eddy simulations to analytical models

Autor: Jézéquel, Erwan
Přispěvatelé: Institut National Polytechnique de Toulouse - Toulouse INP (FRANCE)
Jazyk: angličtina
Rok vydání: 2022
Předmět:
Popis: Wind turbines are often clustered in wind farms where they are subject to the wakes emitted by the upstream rotors. Wind turbine wakes are regions of decreased wind velocity and increased turbulence (velocity variations), that respectively lead to a loss of production and a decreased life expectancy, in the end increasing the cost of wind power. The wind farm layouts must thus be optimised by taking wakes into account to make the wind power more efficient. Since optimisation studies require a lot of simulations, steady analytical models have been developed to quickly provide an estimation of the velocity and turbulence in the wake of a wind turbine, and compute the effect on the downstream rotor. Moreover, wind turbine wakes interact with the atmospheric boundary layer (ABL). Depending on the atmospheric stability, large-scale turbulent motions are created in the ABL that induce lowfrequency displacements of the wake. This phenomenon, called meandering, modi�es the mean wake properties but is rarely taken into account explicitly in steady analytical models. The present work aims at better understanding and modelling the interactions between wind turbine wakes and the ABL, based on high-fidelity numerical simulations. The first part of the manuscript is dedicated to the state-of-the-art. It starts by describing the general fluid dynamic and meteorological concepts on which is based the whole work. Then, we propose a literature review of the wakes and their interactions with the ABL. We also describe the existing steady analytical models and the models for wake meandering. This part ends with a description of our high-fidelity code, Meso-NH, as well as the chosen parametrisation for the turbine. In the second part, we focus on the high-fidelity simulations. A validation of Meso-NH against measurements and other equivalent codes of the community is performed, for three cases of atmospheric stability: neutral, stable and unstable. After a comparative study of different post-processing methods, an in-depth physical analysis of the wakes under these three conditions is proposed. We concluded that atmospheric stability mainly affects the wake meandering, and not the wake expansion which is attributed to the operating conditions. The third part is based on this result. We separate the turbulence and velocity fields into dfferent terms that can be associated to meandering, wake expansion, or both. These terms are compared for the different cases and a model is proposed for the preponderant ones. It results in a new steady analytical model for velocity and turbulence that independently takes into account wake expansion and meandering. This thesis thus presents and analyses new results that enhance our understanding of the behaviour of wakes in the ABL, and proposes a new steady model that allows taking into account wake meandering.
Databáze: OpenAIRE