Dissertation Body

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VORTEX INDUCED VIBRATION OF A RIGID SUBSEA JUMPER 2011 OLUFIDIPE OYEYINKA TOPE i VORTEX INDUCED VIBRATION OF A RIGID SUBSEA JUMPER OLUFIDIPE, Oyeyinka Tope MSc Subsea Engineering and Management (109049739) This project is submitted in partial fulfilments of the requirements for the degree of Master of Science in Subsea Engineering and Management at Newcastle University, Newcastle upon Tyne. VORTEX INDUCED VIBRATION OF A RIGID SUBSEA JUMPER 2011 OLUFIDIPE OYEYINKA TOPE ii DECLARATION I, Olufidipe Oyeyinka Tope, a postgraduate student of the School of Marine Science and Technology, Newcastle University hereby declare - That this dissertation is my own original work and sourced material have been referenced therein; - That it has been prepared specifically as part of the requirements of the fulfilment of a Master Degree of the University of Newcastle and has not been submitted for the same purpose either in this university or any other. Olufidipe Oyeyinka Tope 9th August, 2011 VORTEX INDUCED VIBRATION OF A RIGID SUBSEA JUMPER 2011 OLUFIDIPE OYEYINKA TOPE iii ABSTRACT Vortex Induced Vibration (VIV) plays a very major role in the exploitation and production of offshore oil and gas reserves. This is due to the interactions that take place between offshore equipment and their environments. A rigid jumper is a typically a series of short sections of pipes connected together that span between production equipments offshore. These spans are exposed to ocean currents from which their interactions with cause them to experience VIV. The present work seeks to validate the increasing awareness that rigid subsea jumpers are in fact susceptible to the conditions of VIV. The present work comprises of a study of the flow around a two dimensional (2D) smooth circular cylinder numerically using the 2D Unsteady Reynolds Averaged Navier Stokes (URANS) equations with a Shear Stress Transport (SST k-) turbulence model; structural properties (natural frequencies) and a semi empirical response model in order to obtain the response of a rigid subsea jumper exposed to a steady current of Reynolds Number in the sub-critical regime (1.0 104 1.3 105). The amplitude of the in-line response of the jumper was found to be about 10% of the cross flow response albeit with greater intensities. The numerical study of the flow past the cylinder also agree remarkably well with experimental data as obtained from literature. VORTEX INDUCED VIBRATION OF A RIGID SUBSEA JUMPER 2011 OLUFIDIPE OYEYINKA TOPE iv ACKNOWLEDGEMENT I would like to use this medium to acknowledge the support of numerous individuals who have directly or indirectly contributed to the success of this project. My sincere appreciation goes to Dr. I.M. Viola for his tutelage, guidance and support in his capacity as my Project supervisor. My strong appreciation goes to my parents, and my siblings. This project would not have been as a huge a success it is was it not for the constant support of my friends. They without mentioning a long list of names have been a fortress on which I relied on through this difficult time of putting this together. Finally, to my colleagues on the MSc Subsea Engineering and Management Programme at the School of Marine Science and Technology, it has been a wonderful year. For those too numerous to mention, I would like to say thank you all and God bless. VORTEX INDUCED VIBRATION OF A RIGID SUBSEA JUMPER 2011 OLUFIDIPE OYEYINKA TOPE v TABLE OF CONTENTS VORTEX INDUCED VIBRATION OF A RIGID SUBSEA JUMPER.................................... i DECLARATION ....................................................................................................................... ii ABSTRACT ............................................................................................................................. iii ACKNOWLEDGEMENT ........................................................................................................ iv TABLE OF CONTENTS ........................................................................................................... v LIST OF FIGURES .................................................................................................................. ix LIST OF TABLES .................................................................................................................... xi CHAPTER ONE ........................................................................................................................ 1 1.0 INTRODUCTION ....................................................................................................... 1 1.1 PROJECT CASE ......................................................................................................... 2 1.2 PROJECT OBJECTIVES ........................................................................................... 3 1.3 PROJECT STRUCTURE ............................................................................................ 4 CHAPTER TWO ....................................................................................................................... 5 2.0 BACKGROUND ......................................................................................................... 5 2.1 IMPORTANT PARAMETERS .................................................................................. 7 2.1.1 REYNOLDS NUMBER ...................................................................................... 7 2.1.2 REDUCED FLOW VELOCITY ......................................................................... 7 2.1.3 STROUHAL NUMBER ...................................................................................... 7 2.1.3 STABILITY PARAMETER ................................................................................ 8 2.1.4 DAMPING RATIO .............................................................................................. 8 2.1.4 MASS RATIO ..................................................................................................... 9 2.1.5 ADDED MASS .................................................................................................... 9 2.1.6 EIGEN FREQUENCY AND MODE .................................................................. 9 CHAPTER THREE ................................................................................................................. 11 3.0. FLOW PAST A BLUFF BODY ............................................................................... 11 3.1 VORTEX SHEDDING AND VORTEX INDUCED VIBRATIONS (VIV) ........... 12 VORTEX INDUCED VIBRATION OF A RIGID SUBSEA JUMPER 2011 OLUFIDIPE OYEYINKA TOPE vi 3.2 REYNOLDS NUMBER AND VORTEX SHEDDING ........................................... 13 3.3 FORCES DUE TO VORTEX INDUCED VIBRATIONS ....................................... 15 3.3.1 FLUCTUATING LIFT ...................................................................................... 16 3.4 RESPONSE MODELLING ...................................................................................... 18 3.5 FLOW AND FLOW FIELD MODELLING ............................................................ 19 3.5.1 GOVERNING EQUATIONS ........................................................................ 20 3.6 TURBULENCE ........................................................................................................ 22 3.7 SUBSEA JUMPERS AND VORTEX INDUCED VIBRATIONS .......................... 24 3.7.1 RESPONSE MODELLING OF RIGID JUMPERS .......................................... 25 3.7.2 COUPLED STRUCTURAL AND FLUID ANALYSIS OF A COMPLEX SUBSEA JUMPER .......................................................................................................... 28 CHAPTER FOUR .................................................................................................................... 30 4.0 INTRODUCTION ..................................................................................................... 30 4.1 NUMERICAL SIMULATION OF THE FLOW PAST A CYLINDER .................. 30 4.2 TURBULENCE MODELLING ................................................................................ 31 4.3 GRID DESIGN ......................................................................................................... 31 4.3.1 NEAR WALL TREATMENT ........................................................................... 33 4.4 GOVERNING EQUATIONS ................................................................................... 35 4.5 BOUNDARY CONDITIONS ................................................................................... 37 4.6 COMPUTATIONAL DOMAIN ............................................................................... 37 4.6.1 DESCRIPTION OF THE FLOW CASE ........................................................... 37 4.6.2 FLUID PROPERTIES ....................................................................................... 38 4.6.3 FLOW PHYSICS ............................................................................................... 38 4.7 CASE SETUP ........................................................................................................... 39 4.8 SOLUTION METHODS........................................................................................... 39 4.9 TIME STEP SIZE CONSIDERATION .................................................................... 40 4.10 POWER SPECTRAL DENSITY .......................................................................... 41 VORTEX INDUCED VIBRATION OF A RIGID SUBSEA JUMPER 2011 OLUFIDIPE OYEYINKA TOPE vii 4.11 MODAL ANALYSIS ............................................................................................ 42 4.12 RESPONSE MODELLING .............