Wind Energy

Wind Energy Research

Personnel:

Dr. Ziaul Huque, Group Lead and Co-PI, Department of Mechanical Engineering

Introduction:

In order for wind energy to be a viable alternate energy source and compete with fossil fuels, it is extremely important to optimize production efficiency by determining the optimum shape of the turbine blades along with the appropriate materials used to construct the blades. The major objective of this subproject is to determine the optimum design of wind turbine blades by applying multi-objective techniques with surrogate models. There will be three major tasks towards this objective. They are as follows: (1) to improve understanding of the complex flow field around wind turbine blades and determine the relevant aerodynamic loads on the blades. The major focus of this subtask will be to use computational fluid dynamics (CFD) simulations, though initially Blade Element Momentum (BEM) theory will also be used; (2) to perform structural analysis of the turbine blades using Finite Element Method (FEM). The various aerodynamic loads obtained from the first subtask will be incorporated into the structural analysis model; and (3) to perform multi-objective optimization of the rotor blades using surrogate models. In order to accomplish the three above mentioned tasks several smaller sub tasks have been completed and are mentioned below.

Optimization of Wind Turbine Airfoil Using Genetic Algorithm

  • A Computational Fluid Dynamics (CFD) and response surface-based multiobjective design optimization were performed for six different 2D airfoil profiles, and the Pareto optimal front of each airfoil is presented.
  • FLUENT was used to determine the relevant aerodynamic loads.
  • The Lift Coefficient (CL) and Drag Coefficient (CD) data at a range of 0to 12angles of attack (α) and at three different Reynolds numbers (Re = 68459, 479210 and 958422) for all the six airfoils were obtained.
  • Elitist Non-dominated Sorting Genetic Algorithm (NSGA-II) was used to determine the Pareto optimal set based on the response surfaces
  • The Pareto solution set is presented in the form of a Pareto optimal front.

2D Discrete Optimization of Wind Turbine Blade Airfoil

  • This work is focused on optimization of wind turbine blade profile by two dimensional flow field analysis.
  • A multi-objective response surface technique with computational fluid dynamics (CFD) was performed on two dimensional wind turbine blade airfoil.
  • Based on the data of National Renewable Energy Laboratory (NREL) phase VI wind turbine rotor, six different airfoils were used to calculate different aerodynamic loads (lift & drag) and their effects.
  • Finally a discrete optimization technique was developed to find an optimal airfoil that gives satisfactory performance in a wide range of design conditions.

Numeric Investigation of Compressible Flow

  • This work deals with the numeric analysis of compressible flow around National Renewable Energy Laboratory (NREL) phase VI wind turbine blade airfoil S809.
  • We considered a subsonic flow (mach no. 0.8) and determined the impact of this flow under seven different angle of attacks.
  • The results show that shock takes place just after the mid span at the top surface and just before the mid span at the bottom surface. Slowly this transforms their position as angle of attack increases.
  • Flow separation is also calculated along the airfoil.

  • Shock Propagation on Wind Turbine Airfoil Under Compressible Flow
  • Although wind turbine airfoils are low Reynolds number airfoil, a reasonable investigation of compressible flow under extreme condition might be helpful.
  • A subsonic flow (mach no. C= 0.8) has been considered for this analysis and the impacts of this flow under seven different angle of attacks have been determined.
  • The results show that shock takes place just after the mid span at the top surface and just before the mid span at the bottom surface at zero angle of attack.
  • Slowly the shock waves translate their positions as angle of attack increases.
  • The complex flow phenomena affects lot of fundamental properties of fluid such as density, temperature and pressure.
  • Variation of Turbulent viscosity ratio and surface Y+ have also been determined.

Isogeometric Analysis of Wind Turbine Blade Airfoil

  • This work is focused on isogeometric analysis of wind turbine blade profile by two dimensional flow field analysis.
  • Basis function generated from Non-Uniform Rational B-Splines (NURBS) are employed to construct an exact geometric model of wind turbine blade airfoil. S809 airfoil.
  • NURBS based simulation is done in order to extract more reliable result from the CFD analysis.
  • Due to the use of NURBS based geometry it has been observed that the quality of boundary layer meshes have been improved significantly and accurately.
  • It has been observed that the CFD result gives more realistic solution due to isogeometric analysis and NURBS based mesh refinement and the simulated results have good agreement with experimental results.

Fluid Solid Interaction on Wind Turbine Blade

  • The work is focused on numeric modeling of aerodynamic load developed in a wind turbine blade and its effects on aeroelastic characteristic of wind turbine blade.
  • Geometry is modeled with actual blade data for both twist and tapper. Blade tip is not considered during the modeling.
  • Finally the aerodynamic load obtained from the CFD simulation is transferred for the structural analysis.
  • It has been found that the load distribution along the blade span is not linear. It varies with the span length and it also varies along the chord of the blade airfoil.
  • It has also been observed that the aerodynamic characteristic such as lift coefficient (CL) and pressure coefficient (CP) changes with the deflection of the blade which affects the power output of the wind turbine.

 

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