MATHEMATICAL MODELING OF WAVE-CURRENT INTERACTIONS IN MARINE CURRENT TURBINES by Amit J. Singh A Thesis Submitted to the Faculty of The College of Engineering and Computer Science in Partial Fulfillment of the Requirements for the Degree of Master of Science Florida Atlantic University Boca Raton, Florida May 2012 MATHEMATICAL MODELING OF WAVE-CURRENT INTERACTIONS IN MARINE CURRENT TURBINES by Amit J. Singh This thesis was prepared under the direction of the candidate's thesis advisor, Dr. Madasamy Arockiasamy, Department of Civil, Environmental and Geomatics Engineering, and has been approved by the members ofhis supervisory committee. It was submitted to the faculty of the College of Engineering and Computer Science and was accepted in partial fulfillment ofthe requirements for the degree ofMaster ofScience. SUPERVISORY COMMITTEE: M. Arockiasamy, Ph.D., Thesis Advisor ~u;;; Panagiotis D. Scarlatos, Ph.D. C·, epartment ICiv·l, Environmental and Geomatics Engineering ohammad I, PIi.D. Interim Dean, ollege ofEngineering and Computer Science ~]1>~~ Barry T. Rosson, Ph.D. Dean, Graduate College ii ACKNOWLEDGEMENTS The work presented herein has been supported financially by the Southeast National Marine Renewable Energy Center (SNMREC) and the author gratefully acknowledges the support. The author would like to thank Susan Skemp, Executive Director, and Dr. H.P. Hanson, Scientific Director for the constant encouragement. The author wishes to express his sincere thanks to his thesis advisor Dr. M. Arockiasamy, Professor and Director, Center for Infrastructure and Constructed Facilities, Department of Civil, Environmental, and Geomatics Engineering, for his excellent guidance, suggestions, and constant review in all stages throughout the course of this work. Grateful acknowledgements are due to Dr. Yan Yong and Dr. Chaouki Ghenai for their interest, encouragement, and manuscript review. The author expresses sincere appreciation to Ben Oliver, Lin, and Rammone Bartlett from the Department of Ocean and Mechanical Engineering for their graceful assistance in using the ANSYS software. Finally, I am most grateful for the support, affection, and encouragement from my parents, family and friends throughout the course of the research. iii ABSTRACT Author: Amit J. Singh Title: Mathematical Modeling of Wave-Current Interactions in Marine Current Turbines. Institution: Florida Atlantic University Thesis Advisor: Dr. M. Arockiasamy Degree: Master of Science Year: 2012 The concept of marine current turbines was developed by Peter Fraenkel in the early 1970s. Ever since Fraenkel’s efforts to modify and test the technology, several worldwide agencies have been exploiting the technology to retrofit the marine current turbine to their particular application. The marine current turbine has evolved from generating a few kilowatts to a few gigawatts. The present study focuses on a megawatt sized turbine to be located offshore the coast of Ft. Lauderdale, Florida. The turbine is to be placed in a similar location as a 20 kW test turbine developed by the Southeast National Marine Renewable Energy Center (SNMREC) at Florida Atlantic University, Dania Beach FL. Data obtained from the SNMREC is used in the mathematical model. ANSYS FLUENT is chosen as the CFD software to perform wave-current interaction simulation for the present study. The turbine is modeled in SolidWorks, then meshed in ANSYS ICEM CFD, then run in FLUENT. The results obtained are compared to iv published work by scholarly articles from Fraenkel, Barltrop and many other well known marine energy researchers. The effects of wave height on the turbine operation are analyzed and the results are presented in the form of plots for tip speed ratio and current velocity. v MATHEMATICAL MODELING OF WAVE-CURRENT INTERACTIONS IN MARINE CURRENT TURBINES CHAPTER 1 ....................................................................................................................... 1 1.1 Background .......................................................................................................... 1 1.2 Scope of the Thesis .............................................................................................. 2 1.3 Environmental Impacts ........................................................................................ 3 1.4 Computational Fluid Dynamics (CFD) Analysis ................................................. 4 1.5 Structure of the Report ......................................................................................... 6 CHAPTER 2 ....................................................................................................................... 7 2.1 Introduction .......................................................................................................... 7 2.1.1 Short Term and Long Term Effects on Wind Turbines ........................................... 7 2.2 Marine Current Energy Resource ........................................................................ 8 2.3 Power Extraction ................................................................................................ 12 2.3.1 Admiralty Inlet ocean current data analysis ........................................................... 13 2.3.2 Metaocean Data for Southeast Florida ................................................................... 16 2.4 Marine Current Extraction Technologies ........................................................... 21 2.5 Power from Marine Current Turbines ................................................................ 27 2.6 Rotor Blade Types ............................................................................................. 35 2.6.1 Axial Flow Rotor Blade Design ............................................................................. 36 2.7 Hydrodynamics .................................................................................................. 37 2.7.1 Wind Turbine Operation Modeling Using CFD .................................................... 37 2.7.2 Marine Turbine Operation Modeling Using CFD .................................................. 41 2.7.3 Wave Current Interactions ..................................................................................... 41 CHAPTER 3 ..................................................................................................................... 44 3.1 Introduction ........................................................................................................ 44 3.2 Flow Characteristics ........................................................................................... 45 3.3 Computational Fluid Dynamics ......................................................................... 47 vi 3.4 Basics of Fluid Flow in ANSYS FLUENT ........................................................ 48 3.5 Multiphase Flow ................................................................................................ 49 3.5.1 The VOF Model ..................................................................................................... 54 3.5.2 The Mixture Model ................................................................................................ 74 3.5.3 The Eulerian Model ............................................................................................... 74 3.6 The Finite Element Method ............................................................................... 75 3.7 Blade Element Momentum Theory .................................................................... 76 3.8 Principles of Similitude ...................................................................................... 77 CHAPTER 4 ..................................................................................................................... 78 4.1 Introduction ........................................................................................................ 78 4.2 Physical Properties of Fluids.............................................................................. 79 4.3 Fluid Flow in Marine Current Turbines ............................................................. 84 4.3.1 Compressible or Incompressible flow .................................................................... 85 4.3.2 Laminar and Turbulent Flow ................................................................................. 86 4.4 Modeling the Rotor Blade and Hub using SolidWorks ..................................... 87 4.5 Creation of Domain and all its Entities using ANSYS ICEM CFD................... 91 4.5.1 Blade Geometry Manipulation ............................................................................... 91 4.5.2 Computational Fluid Domain ................................................................................. 92 4.5.3 Multiphase Domain ................................................................................................ 93 4.6 Meshing the Domain and Blade ......................................................................... 99 4.6.1 Mesh Type Selection .............................................................................................. 99 4.6.2 Multiphase Mesh Setup ........................................................................................ 100 4.7 CFD Simulation using ANSYS FLUENT ....................................................... 106 4.7.1 Multiphase Flow CFD .......................................................................................... 106 CHAPTER 5 ..................................................................................................................