Meteorologically Driven Wind Turbine SimulationEvan Greer, Mentor: Dr. Marcelo Kobayashi, HARP REU ProgramAugust 2, 2012Contact: evantk@hawaii.edu

globalwindgroup.com

Overview

Introduction and Motivations Creating the geometry Stationary study of turbine geometry Rotating study of turbine geometry Future Plans Acknowledgements

Introduction

Energy Security

High reliability of fossil fuels leads to wide spread use

Set amount of fossil fuel outputs a set amount of energy

Motivations

Introduction of reliability to renewable resources, wind energy in particular

Wind energy is subject to low reliability due to changing weather conditions

Scale predictions of large scale weather patterns to make predictions about the environment around the turbine

The effects of local topography on efficiency will be studied

WRF (weather research and forecasting) model coupled with CFD models

This is the future goal of this research but first a working model of the turbine must be created and studied

Initial studies

Used a sample geometry from Comsol Multiphysics

Played with initial conditions and mesh sizes

Learned how to use the Comsol Multiphysics software Studied introductory tutorial

building a busbar geometry Learned how to set up fluid

flow and thermoelectric physics

Setting up the geometry

• Approximated the geometry of a typical wind turbine

• Height of the tower set at 300 ft

•Length of the rotors set at 200 ft

•Length of the nacelle set at 40 ft

Front View Side View

Blade Domain

• Created for the implementation of the sliding mesh

• Cylindrical region with a height of 80 ft encompassing the blades

• Domain to move with the blades

Flow Domain

• Region where boundary and initial conditions are to be defined

• Created a cylindrical region behind the sliding region to study wake

• Material for the flow set as air and material for turbine set as aluminum

Setting up the mesh

• Generated mesh using tetrahedral elements

•Mesh had to be refined around blades

•Mesh consisted of 93349 elements

Stationary study

Ran a stationary turbulent flow study using a k-ε model

This model has the purpose of understanding how fluid flow is affected by geometry

Setting up physics

Used a simple turbulent flow physical model

Stationary study step with no time dependence

Inlet velocity of 3.219 m/s, this is the average annual wind speed of Honolulu reported by NOAA [1]

Outlet condition was also set to atmospheric pressure

Also, a volume force was introduced on the flow domain

Results

The Rotating Model

Used Rotating Machinery, Turbulent Flow physical model

Moving domains are coupled with stationary domains by identity pairs

At these identity pairs, a flux continuity boundary condition is applied

Navier-Stokes equations are formulated based on rotating and stationary coordinate systems

Issues

Convergence of time stepped solution

Solution would get stuck on calculation of time step

Many issues with script files and runs on supercomputer

Supercomputing issues

Issues with licensing Jobs would terminate because of lack of

licensing on multiple nodes Solved with batch and cluster computing add-on

to job configurations within Comsol Issues with node communication

Comsol would get kicked nodes Solved using MPD (Multi processing Daemon)

used by Comsol to communicate between nodes Accomplished through modification of script files

with the help of Andrew Yukitomo

Simplification

Isolated rotating geometry

Try to get rotating blade working without pairing

Added input and output condition

Modifications

Added pairing and flow continuity condition between stationary and rotating domains

Used overlapping domains and input and output conditions

Results

Further modifications

Used non-overlapping domains

Got rid of input and output conditions, instead used a pressure point constraint

Increased number of iterations used by the solver

The Next Steps

Complete the set up of the full rotating geometry

Get the blade study to run for larger time scales Further work needs to be done to understand where

and why the convergence errors are occurring Understanding how to make a more accurate mesh

Introduce the stationary wake region and a two dimensional pairing region

Introduce the flow domain and three dimensional pairing and get the complete model to run

Get the rotation of the turbine to be dictated by inlet velocity conditions This will involve delving deeper into the

interface to understand how to program physical models

Future Plans

Project benchmarks: Creating geometry Modeling stationary case Implementation of sliding mesh Implementation of Large Eddy

Simulation Implementation of WRF data

This research will be continued under a NASA space grant in the fall

Acknowledgements

I would like to thank Dr. Susan Brown for giving me the opportunity to be a part of this program and Dr. Marcelo Kobayashi for his continued support and allowing me to share in his research. I also want to acknowledge Andrew Yukitomo for his continued help with script files and supercomputing issues and HOSC for allowing us to use the supercomputing facilities for our work.

"This material is based upon work supported by the National Science Foundation under Grant No. 0852082. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation."

References

[1] Delliger, Dan, 2008, Average Wind Speed, Comparative Climate Data, http://lwf.ncdc.noaa.gov/oa/climate/online/ccd/avgwind.html (July 5, 2012)

[2] Laminar Flow in a Baffled Stirred Mixer. Comsol Multiphysics 4.3 sample program documentation, 2012