A Computational Analysis of Wind Turbine and Wind Farm Aerodynamics with a Focus on Dual Rotor Wind Turbines

dc.contributor.advisor Anupam Sharma
dc.contributor.author Rosenberg, Aaron
dc.contributor.department Aerospace Engineering
dc.date 2018-08-11T10:17:09.000
dc.date.accessioned 2020-06-30T03:08:01Z
dc.date.available 2020-06-30T03:08:01Z
dc.date.copyright Fri Jan 01 00:00:00 UTC 2016
dc.date.embargo 2001-01-01
dc.date.issued 2016-01-01
dc.description.abstract <p>This dissertation serves to summarize my research into wind farm and wind turbine aerodynamics.</p> <p>Included in this thesis is a summary of the methods I use as well as the four research problems that I investigated.</p> <p>Motivation is provided for my research as well as an overview of the computational</p> <p>methods that I use. These methods include analytical methods such as blade element</p> <p>momentum (BEM) theory and the vortex lattice method as well as computational fluid dynamic methods like</p> <p>the Reynolds averaged Navier-Stokes (RANS) equations and large eddy simulation (LES). These methods are used</p> <p>to investigate wind turbine and wind farm aerodynamics. In particular, I use these methods to confront the</p> <p>various forms of loss that wind turbines and wind farms experience. They include the losses that individual turbines</p> <p>experience due to swirl, induction, and viscosity as well as the loss that wind farms experience due to turbine-wake interaction.</p> <p>Horizontal axis wind turbines (HAWTs) suffer</p> <p>from aerodynamic ineffciencies in the blade root region (near the hub) due to several non-aerodynamic</p> <p>constraints. Aerodynamic interactions between turbines in a wind farm also lead to signifcant loss of wind</p> <p>farm efficiency. A new dual-rotor wind turbine (DRWT) concept is proposed that aims at mitigating these two</p> <p>losses. A DRWT is designed that uses an existing turbine rotor for the main rotor, while the secondary rotor</p> <p>is designed using a high lift-to-drag ratio airfoil. Reynolds Averaged Navier-Stokes computational fluid</p> <p>dynamics simulations are used to optimize the design. Large eddy simulations confirm the increase energy</p> <p>capture potential of the DRWT. Wake comparisons however do not show enhanced entrainment of axial momentum.</p> <p>I extend the prescribed wake vortex lattice method (VLM) to</p> <p>perform aerodynamic analysis and optimization of dual-rotor wind turbines.</p> <p>The additional vortex system introduced</p> <p>by the secondary rotor of a DRWT is modeled while taking into account the</p> <p>singularities that occur when the trailing vortices from the secondary</p> <p>(upstream) rotor interact with the bound vortices of the main (downstream)</p> <p>rotor. Pseduo-steady assumption is invoked and averaging over multiple</p> <p>relative rotor positions is performed to account for the primary and</p> <p>secondary rotors operating at different rotational velocities. This</p> <p>implementation of the VLM is first validated against experiments and blade</p> <p>element momentum theory results for a conventional, single rotor turbine. The</p> <p>solver is then verified against RANS CFD</p> <p>results for two DRWTs. Parametric sweeps are performed using the proposed VLM</p> <p>algorithm to optimize a DRWT design. The problem with the algorithm at high</p> <p>loading conditions is highlighted and a solution is proposed that uses RANS</p> <p>CFD results to calibrate the VLM model.</p> <p>In addition to wake losses, aerodynamic interaction between</p> <p>turbines in wind farms leads to surface flow convergence . This phenomenon has been</p> <p>observed in field tests with surface flux stations. A hypothesis is</p> <p>proposed to explain this surface flow convergence phenomenon - incomplete</p> <p>pressure recovery behind a turbine leading to successive pressure drops in</p> <p>tightly-spaced turbine arrays leads to drop in overall pressure deep inside</p> <p>a wind plant; this low-pressure acts as an attractor leading to flow</p> <p>convergence. Numerical investigations of the phenomenon of surface flow</p> <p>convergence are carried out that support this hypothesis. An actuator disk</p> <p>model to represent wind turbines in an LES</p> <p>CFD solver is used to simulate hypothetical wind plants. The flow</p> <p>convergence phenomenon reflects as change in flow velocity direction and is</p> <p>more prominent near the ground than at turbine hub height.</p> <p>Numerical simulations of wind plant aerodynamics are conducted with various</p> <p>approximations to investigate and explain the flow convergence phenomenon.</p>
dc.format.mimetype application/pdf
dc.identifier archive/lib.dr.iastate.edu/etd/16004/
dc.identifier.articleid 7011
dc.identifier.contextkey 11169519
dc.identifier.doi https://doi.org/10.31274/etd-180810-5631
dc.identifier.s3bucket isulib-bepress-aws-west
dc.identifier.submissionpath etd/16004
dc.identifier.uri https://dr.lib.iastate.edu/handle/20.500.12876/30187
dc.language.iso en
dc.source.bitstream archive/lib.dr.iastate.edu/etd/16004/Rosenberg_iastate_0097E_15794.pdf|||Fri Jan 14 20:53:48 UTC 2022
dc.subject.disciplines Aerospace Engineering
dc.subject.keywords Aerodynamics
dc.subject.keywords CFD
dc.subject.keywords Wind Energy
dc.subject.keywords Wind Farm
dc.subject.keywords Wind Turbine
dc.title A Computational Analysis of Wind Turbine and Wind Farm Aerodynamics with a Focus on Dual Rotor Wind Turbines
dc.type article
dc.type.genre dissertation
dspace.entity.type Publication
relation.isOrgUnitOfPublication 047b23ca-7bd7-4194-b084-c4181d33d95d
thesis.degree.discipline Aerospace Engineering
thesis.degree.level dissertation
thesis.degree.name Doctor of Philosophy
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