Meteorologically Driven Wind Turbine Simulation

1. Evan Greer, Mentor: Dr. Marcelo Kobayashi, HARP REU Program August 2, 2012 Contact: evantk@hawaii.edu globalwindgroup.com Meteorologically Driven Wind Turbine Simulation

2. Overview • Introduction and Motivations • Creating the geometry • Stationary study of turbine geometry • Rotating study of turbine geometry • Future Plans • Acknowledgements

3. Introduction • Energy Security • High reliability of fossil fuels leads to wide spread use • Set amount of fossil fuel outputs a set amount of energy

4. 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

5. 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

6. Initial studies • Used a sample geometry from ComsolMultiphysics • Played with initial conditions and mesh sizes • Learned how to use the ComsolMultiphysics software • Studied introductory tutorial building a busbar geometry • Learned how to set up fluid flow and thermoelectric physics

7. 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

8. Side View Front View

9. 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

11. 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

12. Setting up the mesh • Generated mesh using tetrahedral elements • Mesh had to be refined around blades • Mesh consisted of 93349 elements

13. 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

14. 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]

15. Outlet condition was also set to atmospheric pressure • Also, a volume force was introduced on the flow domain

16. Results

19. 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

20. Issues • Convergence of time stepped solution • Solution would get stuck on calculation of time step • Many issues with script files and runs on supercomputer

21. 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

22. Simplification • Isolated rotating geometry • Try to get rotating blade working without pairing • Added input and output condition

23. Modifications • Added pairing and flow continuity condition between stationary and rotating domains • Used overlapping domains and input and output conditions

24. Results

27. 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

29. 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

30. 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

31. 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

32. 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."

33. 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. ComsolMultiphysics 4.3 sample program documentation, 2012