Title: On the interaction of a wind turbine wake with a conventionally neutral atmospheric boundary layer

Abstract

In this work, we investigate the dynamics of wind turbine tip-vortex breakdown in a conventionally neutral atmospheric boundary layer (ABL). To this end, high-resolution data are collected from large-eddy simulations of a wind turbine operating within a neutral ABL and studied by means of proper orthogonal decomposition (POD) and Fourier analysis. The high resolution of the generated data in both space and time allows us to gain insight into the tip-vortex breakdown mechanisms by (i) capturing the energy modes of the coherent structures, (ii) studying their contribution to the tip-vortex breakdown through their power spectra functions and mean kinetic energy (MKE) flux, and (iii) analysing the growth rate of each contributing perturbation frequency along tip vortices. Our analysis shows that under a fully turbulent scenario, the growth rate of perturbations along the tip vortices is largest for low wave numbers, i.e. long-wave perturbations. Additionally, the MKE flux reaches its highest value at two diameters downstream of the rotor plane, a behaviour that can be attributed to the coexistence of multiple interacting POD modes, with the streamwise vortex roller mode being the primary contributor to the total MKE flux budget, contributing approximately . Finally, comparisons with a laminar, uniform flow scenariomore » subject to a single-frequency perturbation highlight the differences between the two ambient flow conditions. In the non-turbulent, uniform flow scenario, the growth rate attains its maximum value at a wave number corresponding to the out-of-phase mutual-inductance mechanism, whereas the MKE flux exhibits local minima and maxima along the wake and at different downstream locations depending on the perturbation frequency. Our analyses suggest that the breakdown of the wind turbine tip vortices under a fully turbulent neutral ABL inflow is due to complex interactions across a range of excitation frequencies, in which the mutual-inductance instability may not be the dominant one.« less

Authors:

Hodgkin, Amy  ^[1];

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• Search DOE PAGES for ORCID "0000-0002-6596-0286"

Deskos, Georgios  ^[2];

• Search DOE PAGES for author "Deskos, Georgios"
• Search DOE PAGES for ORCID "0000-0001-7592-7191"

Laizet, Sylvain ^[1]

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+ Show Author Affiliations

1. Imperial College, London (United Kingdom)
2. National Renewable Energy Laboratory (NREL), Golden, CO (United States)

Publication Date:

Wed May 31 00:00:00 EDT 2023

Research Org.:

National Renewable Energy Laboratory (NREL), Golden, CO (United States)

Sponsoring Org.:

USDOE Office of Energy Efficiency and Renewable Energy (EERE), Renewable Power Office. Wind Energy Technologies Office; Engineering and Physical Sciences Research Council (EPSRC)

OSTI Identifier:

1983888

Report Number(s):

NREL/JA-5000-86115
Journal ID: ISSN 0142-727X; MainId:86888;UUID:8424f940-e4d6-48ac-a25a-a1b9d480714b;MainAdminID:69631

Grant/Contract Number:  

AC36-08GO28308

Resource Type:

Accepted Manuscript

Journal Name:

International Journal of Heat and Fluid Flow

Additional Journal Information:

Journal Volume: 102; Journal ID: ISSN 0142-727X

Publisher:

Elsevier

Country of Publication:

United States

Language:

English

Subject:

17 WIND ENERGY; atmospheric boundary layer; large-eddy simulation; proper orthogonal decomposition; wind turbine tip-vortex breakdown