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Effects From Complex Terrain on Wind-Turbine Performance
KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. (STandUP for Wind)
2017 (English)In: Journal of energy resources technology, ISSN 0195-0738, E-ISSN 1528-8994, Vol. 139, no 5, 051205Article in journal (Refereed) Published
Abstract [en]

In this work, experimental measurements are made to study wind turbines over complex terrains and in presence of the atmospheric boundary layer. Thrust and power coefficients for single and multiple turbines are measured when introducing sinusoidal hills and spires inducing an artificial atmospheric boundary layer. Additionally, wake interaction effects are studied, and inflow velocity profiles are characterized using hot-wire anemometry. The results indicate that the introduced hills have a positive impact on the wind-turbine performance and that wake-interaction effects are significantly reduced during turbulent inflow conditions.

Place, publisher, year, edition, pages
ASME Press, 2017. Vol. 139, no 5, 051205
Keyword [en]
Marine Current Turbines, Boundary-Layer, Wake, Flow, Simulation
National Category
Energy Engineering
Identifiers
URN: urn:nbn:se:kth:diva-215373DOI: 10.1115/1.4036048ISI: 000411139800007Scopus ID: 2-s2.0-85018483540OAI: oai:DiVA.org:kth-215373DiVA: diva2:1147900
Conference
2nd International Conference on Next Generation of Wind Energy (ICNGWE), AUG 24-26, 2016, Lund Univ, Lund, Sweden
Funder
Swedish Research Council
Note

QC 20171009

Available from: 2017-10-09 Created: 2017-10-09 Last updated: 2018-01-22Bibliographically approved
In thesis
1. Wind turbines over a hilly terrain: performance and wake evolution
Open this publication in new window or tab >>Wind turbines over a hilly terrain: performance and wake evolution
2018 (English)Licentiate thesis, comprehensive summary (Other academic)
Alternative title[sv]
Vindturbiner över en kuperad terräng: prestanda och vakutbredning
Abstract [en]

The aim of this licentiate thesis is to investigate wind-turbines placed in a complex-terrain environment. This is done by studying the flow around small-scale wind-turbine models placed over a landscape model with hills, and by comparing the results with corresponding data obtained over a flat terrain model. The studied flow features include the wind-turbine wake development and the turbine performance under different conditions, the effects from wake interactions, the influence of the ambient turbulence levels and the influence from a complex topography. Wind-tunnel measurements have been performed using particle image velocimetry and hot-wire anemometry to measure the velocity field. Additionally, numerical simulations, based on RANS modelling and actuator-disc techniques, have been made to support the experimental data and to gain further knowledge about the investigated flow cases.

The results reveal that the hills promote a downward wake deflection behind the turbines and enhance the wind-turbine wake diffusion. As a consequence of this, and with the flow acceleration introduced by the hills, an improved power performance is seen for turbines exposed to wake-interference effects. A correlation is observed between the turbulence levels present in the flow, and the magnitude to which the hill-induced flow gradients influence the wake: Stronger wake deflections due to the hills are seen when the wind-turbine wake is more diffused. This is for instance the case when the wake of two tandem turbines is studied, or when higher ambient turbulence levels are present in the wind tunnel.

A good qualitative agreement is seen when comparing the experimental and numerical results. The simulation results further indicate that the hills give rise to modulations of the wind-turbine wake. It is shown that these modulations can be reasonably captured by means of wake-superposition techniques, given that a wake model with sufficient accuracy is chosen. 

Abstract [sv]

Syftet med denna licentiatavhandling är att öka förståelsen om hur vindturbiner påverkas av en omgivande komplex terräng. Huvudsakligen betraktas luftströmningen kring småskaliga vindturbinsmodeller som placerats över en landskapsmodell med kullar. I tillägg görs jämförelser med resultat som erhållits då vindtubinerna placerats över en platt landskapsmodell. De studerade strömningsaspekterna inkluderar vindturbinernas vakutveckling och prestanda under olika förhållanden, inverkan från vakinteraktioner, inflytande från omgivande turbulensnivåer och inverkan från en komplex topografi. Vindtunnelmätningar har utf ̈orts där PIV och varmtrådsanemometri användes för att uppmäta hastighetsfält. I tillägg har numeriska simuleringar utförts baserade på RANS-modellering, där turbinens rotor beskrevs av en porös skiva. Simuleringarna gjordes som komplement till de experimentella mätresultaten för att få en ökad förståelse om de undersökta strömningsfallen.

Resultaten från mätningarna och simuleringarna med kullar visar att terrängvariationerna främjar en nedåtgående vakförskjutning bakom turbinerna och ökar vindturbinernas vakdiffusion. Detta, i kombination med luftens acceleration över kullarna, resulterar i att en högre effektprestanda utvinns från en vindturbin vars inströmmande luftflöde störs av vaken från en framförliggande turbin. Vidare observeras kraftigare nedågående vakförskjutningar på grund av det kullriga landskapet då vindturbinsvakarna är mer diffunderade. Detta är exempelvis fallet då vaken bakom två turbiner placerade i en tandemkonfiguration studeras, eller när höga omgivande turbulensnivåer uppmäts i vindtunneln.

En bra kvalitativ överensstämmelse kan ses mellan de experimentella och numeriska resultat som uppnås. Resultaten från simuleringarna indikerar dessutom att landskapet med kullar ger upphov till moduleringar av vindturbinens vak. Det visas att dessa moduleringar kan beskrivas någorlunda väl med hjälp av vaksuperpositionsmetoder, givet att en vakmodell med tillräckligt hög noggrannhet väljs. 

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2018. 56 p.
Keyword
Fluid mechanics, wind turbines, complex terrain, wind-tunnel measurements, Strömningsmekanik, vindturbiner, komplex terräng, vindtunnelmätningar
National Category
Applied Mechanics
Research subject
Engineering Mechanics
Identifiers
urn:nbn:se:kth:diva-221675 (URN)978-91-7729-674-4 (ISBN)
Presentation
2018-02-23, D3, Lindstedtsvägen 5, D-huset, KTH Campus, Stockholm, 10:15 (English)
Opponent
Supervisors
Funder
Swedish Research Council, 2014-5406
Note

QC 20180122

Available from: 2018-01-22 Created: 2018-01-19 Last updated: 2018-01-22Bibliographically approved

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