STUDY OF KINEMATICS OF EXTREME WAVES IMPACTING OFFSHORE AND COASTAL STRUCTURES BY NON INTRUSIVE MEASUREMENT TECHNIQUES A Dissertation by YOUN KYUNG SONG Submitted to the Office of Graduate and Professional Studies of Texas A&M University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Chair of Committee, Kuang-An Chang Co-Chair of Committee, Jennifer L. Irish Committee Members, Richard Mercier Robert Hetland Head of Department, Robin Autenrieth December 2013 Major Subject: Civil Engineering Copyright 2013Youn Kyung Song ABSTRACT Extreme wave flows associated with a large scale wave breaking during interactions with marine structures or complex coastal geography of is one of the major concerns in a design of coastal and ocean structures. In order to properly understand the impact mechanisms of breaking extreme waves, full field evaluations of impacting multiphase flow velocities should be properly conducted first. In this context, this present dissertation experimentally investigated velocity structures of turbulent, multiphase wave flow velocities during active interactions with various offshore and onshore ocean environments. First, initial inundation flow structures of tsunami-like long waves interacting with complex coastal topography are experimentally investigated. Turbulent wave surface velocities were effectively measured by introducing a non-intrusive video imagery technique, the “wave front tracing method”. Three distinctive configurations for patch layouts that vary either in characteristic patch diameter (D) or in center-to-center spacing between patches (ΔS) were employed. That is, patch layouts consisted of six (G1) and twelve (G2), “small” circular macro roughness patches of D =1.2 m and six, “large” circular macro roughness patches (G3) of D = 1.7 m were employed, respectively. A patch layout employed for G1 appears to be effective in reducing the u velocities along the centerlines of the reference patch that consistently decreased to 85% of a convergence velocity U = 2m/s and to 45% of U. However, in the channel, u velocities hardly reduced below the convergence velocity. On the other hand, the patch layout G2 is observed as rather effective in uniformly reducing the u velocities alongshore. The hand, the patch layout G3 is observed as effective in suppressing the alongshore variability in flow behind the frontal patches. This may be due to the "holding-up" effects produced by the large patches holding the flow within the patch for a longer duration. Furthermore, such a "holding- up" effect from G3 appears to induce a large inundation depth in the flow along the opening. Next, green water velocities and dynamic impacts of the extreme ocean waves on a fixed offshore deck structure are investigated. The experiments focused on the impacting waves generated in a large-scale, three-dimensional ocean wave basin. Using the BIV technique, overall flow structures and temporal and spatial distributions of the maximum velocities were successfully evaluated. The most significant spatial variability in mean velocities in the propagating direction was found from the protruding wave front near the center of the deck during early stages of the wave run-up. The maximum front speed of 1.4C was first observed in ii the center of the deck near y = 0 at a midpoint of the deck (x = 0.5L), where C is the wave phase speed. The flow velocities started decreasing below 1C over all fields once the wave frontal flow passed the rear edge and started leaving the deck. Pressure measurements were also conducted at four different vertical positions on vertical measurement planes at three different locations on the horizontal plane. Most of measured pressures showed impulsive impact patterns with sudden rises of pressure peaks. The highest pressure was observed as at x = L/2. Correlations between wave kinematic energy and dynamic pressure were examined to determine the impact coefficients ci'. ci' varied within relatively narrow ranges 0.29 ≤ ci' ≤ 1.56. In the present large scale experiments, the impact pressures on the structures are strongly affected by both variability of flow structures and impulsiveness of impacting waves containing considerable air volumes. Lastly, the study is extended for more violent sloshing wave flows. The study experimentally investigated flow kinematics and impact pressures of a partially filled liquid sloshing flow during the periodic longitudinal motion of a rectangular tank. The horizontal velocities near the free surface reached 1.6C with C being the wave phase speed calculated based on the shallow water assumption. As the tank reached its maximum displacement and about to reverse, the dominant flow changed its direction rapidly to vertical upward after the breaking wave crest impinging on the side wall and forming an up-rushing jet. The vertical velocity of the rising jet reached 3.4C before it impacted the top wall. During the flip-through event as the fast moving wave crest collided with the side wall, the steep wave crest resulted in a focused impact on the side wall at the SWL. The resulting impulsive peak pressure was recorded as about 10ρgh immediately followed by the evident pressure oscillation with a frequency approximately 500 Hz. After the wall impact, the multiphase up-rushing jet shot up and impacted the top wall. The magnitude of the pressure was again about 10ρgh , similar to that recorded by the breaking wave impact on the side wall. Correlating the dynamic impact pressures with the corresponding local maximum flow velocities in the direction normal to the walls was performed by introducing the impact coefficient ci and the modified impact coefficient ci′ , defined as 22 pmax = cViiρρmax = cC′ with Vmax being the magnitude of the maximum local velocities. The average values of the modified impact coefficient ci′ between the side wall impacts and the top wall impacts were nearly identical, with the average value of ci′ = 5.2 . iii DEDICATION This dissertation is dedicated, with love and respect, to my husband and our sister, brothers, and parents. iv AKNOWLEDGEMENTS I would like to first thank my advisor, Dr. Kuang-An Chang, for his guidance and advice. This dissertation could not have been completed without his insight, experience and comments. I also deeply appreciate his continuous encouragement from the beginning of the study. I also would like to thank my advisor, Dr. Jennifer Irish, for her time, leadership and dedication. Her example as a professional researcher will carry with me throughout my career and her commitment to teaching and research was an inspiration. I would like to thank the rest of my committee members, Dr. Richard Mercier, for his continuous guidance and support throughout the course of this research, and Dr. Robert Hetland, for his advice and commitment to teaching. Thanks go to my senior research mate and mentor, Dr. Ho Joon Lim, who and helped me to learn the laboratory methods used in this dissertation and aided in my initial understanding of BIV processing. I would like to thank Yong Uk Ryu and Dr. Kusalika Ariyarathne for their help, friendship and encouragement. Thanks to the staff at Offshore Technology Research Center for their technical support and friendly aids and also wish to thank staff at O.H. Hinsdale Wave Research Laboratory for their assistant and collaboration during my laboratory research. Lastly, I would like to express my special gratitude and love to my husband, Aldric Baquet, my parents, and parents-in-law. I am also thankful to my brother, Min Soo Song, and my sister, Youn Jung Song. This dissertation would not have been possible without their invaluable love, trust, encouragement, and support. v TABLE OF CONTENTS Page ABSTRACT ................................................................................................................................... ii DEDICATION .............................................................................................................................. iv AKNOWLEDGEMENTS .............................................................................................................. v TABLE OF CONTENTS .............................................................................................................. vi LIST OF FIGURES ....................................................................................................................... ix LIST OF TABLES ........................................................................................................................ xi CHAPTER I INTRODUCTION .................................................................................................... 1 I.1 Flow characteristics during extreme wave breaking and interactions with ocean structures ....................................................................................................... 1 I.2 Outlines of this dissertation and objectives of each chapter ................................... 2 CHAPTER II TSUNAMI-LIKE LONG WAVE KINEMATICS AROUND MACRO- ROUGHNESS PATCH TYPE VEGETATION ............................................................................. 3 II.1 Introduction ............................................................................................................. 3 II.1.1 Characteristics of tsunami inundation flows propagating with a turbulent bore front .................................................................................... 3 II.1.2 Flow characteristics within emergent vegetation ......................................