Performance and wake conditions of a rotor located in the wake of an obstacle

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Abstract

Obstacles like forests, ridges and hills can strongly affect the velocity profile in front of a wind turbine rotor. The present work aims at quantifying the influence of nearby located obstacles on the performance and wake characteristics of a downstream located wind turbine. Here the influence of an obstacle in the form of a cylindrical disk was investigated experimentally in a water flume. A model of a three-bladed rotor, designed using Glauert's optimum theory at a tip speed ratio λ = 5, was placed in the wake of a disk with a diameter close to the one of the rotor. The distance from the disk to the rotor was changed from 4 to 8 rotor diameters, with the vertical distance from the rotor axis varied 0.5 and 1 rotor diameters. The associated turbulent intensity of the incoming flow to the rotor changed 3 to '6% due to the influence of the disk wake. In the experiment, thrust characteristics and associated pulsations as a function of the incoming flow structures were measured by strain gauges. The flow condition in front of the rotor was measured with high temporal accuracy using LDA and power coefficients were determine as function of tip speed ratio for different obstacle positions. Furthermore, PIV measurements were carried out to study the development of the mean velocity deficit profiles of the wake behind the wind turbine model under the influence of the wake generated by the obstacle. By use of regression techniques to fit the velocity profiles it was possible to determine velocity deficits and estimate length scales of the wake attenuation.
Original languageEnglish
Article number032051
Book seriesJournal of Physics: Conference Series (Online)
Volume753
Issue number3
Number of pages7
ISSN1742-6596
DOIs
Publication statusPublished - 2016

Keywords

  • Applied fluid mechanics
  • Wakes
  • Flow visualization and imaging
  • Probability theory, stochastic processes, and statistics
  • Fluid mechanics and aerodynamics (mechanical engineering)
  • Statistics
  • Measurement
  • General shapes and structures
  • Mechanical components
  • Power and plant engineering (mechanical engineering)
  • discs (structures)
  • flow visualisation
  • regression analysis
  • rotors (mechanical)
  • strain gauges
  • turbulence
  • wakes
  • wind turbines
  • wake conditions
  • velocity profile
  • wind turbine rotor
  • nearby located obstacles
  • performance characteristics
  • wake characteristics
  • downstream located wind turbine
  • cylindrical disk
  • water flume
  • three-bladed rotor
  • Glauert’s optimum theory
  • tip speed ratio
  • vertical distance
  • rotor diameters
  • rotor axis
  • turbulent intensity
  • disk wake
  • thrust characteristics
  • pulsations
  • incoming flow structures
  • flow condition
  • LDA
  • power coefficients
  • obstacle positions
  • PIV measurements
  • wind turbine model
  • wake attenuation
  • length scales
  • velocity deficits
  • regression techniques

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