Ocean Engineering Commons^™

Numerical Modeling Of Shoreline Response To Storm Tides And Sea Level Rise, Akash Sahu

Civil & Environmental Engineering Theses & Dissertations

In this study, an integrated hydrodynamic, wave, and sediment transport modeling approach is developed for predicting the spatiotemporal variation of erosion of a sandy shoreline due to storm surge, wave action, tidal variations, and relative sea level rise (RSLR). The study site is located at the northern most portion of the city of Norfolk, Virginia, and it is of importance to the city, both in terms of tourism and for the protection that it provides for upland properties against storms. The region, in general, experiences the highest rate of RSLR on the U.S. East Coast which should result in high …

Vulnerability Assessment Of Critical Bridges In The Hampton Roads Region Of Virginia To Storm Surge Flooding Under Sea Level Rise, Luca Castrucci

Civil & Environmental Engineering Theses & Dissertations

In this thesis, a hydrodynamic model was developed to study the vulnerability of the transportation infrastructure in the Hampton Roads region of Virginia to storm surge flooding under sea level rise. The Hampton Roads region is the second most affected area by relative sea level rise in the United States. The hydrodynamic model was validated for tide prediction, and its performance in storm surge simulation was validated with data from Hurricane Irene (2011). The developed model was then applied to eight flood-prone bridges in the transportation network that connect the cities of Norfolk, Hampton, Virginia Beach, Chesapeake and Portsmouth; the …

Parametric Investigation Of A Laboratory Drop Test To Simulate Base Acceleration Induced By Wave Impacts Of High Speed Planing Craft, John D. Barber

Mechanical & Aerospace Engineering Theses & Dissertations

High speed operations in a small craft can be physically punishing and, in some circumstances, even dangerous for the crew. The aspect of small craft operations that make them punishing for the crew is wave slamming generated by wave impacts as the craft is traveling over the seas at high speed.

The initial step of this thesis effort was to perform a literature survey to determine what knowledge existed within the technical and academic community about wave slamming and simulating them with drop tests.

Eventually, a final experiment strongly influenced by the experiment model found in (Protocol 1, 2014) was …

Changing Trends In Wave Heights In The U.S. Mid-Atlantic Region, Hillary Lane

Civil & Environmental Engineering Theses & Dissertations

The pace and effects of climate change are an area of constant focus for coastal engineers as evolving patterns in the atmosphere worldwide affect the oceans and coasts on a regional and global scale. Surface waves respond to changing wind patterns both locally and from propagating swell, and the difficulty in predicting future wind patterns is well-established. Expectations that climate change will result in more frequent and intense coastal storms and consequently greater wave heights in the North Atlantic are still unrealized, and recent forecasts from a variety of atmosphere-ocean coupled global climate models instead predict decreasing wave heights through …

Constrained Discrete Phase Control Of A Heaving Wave Energy Converter In Irregular Seas Using Reinforcement Learning, Praveen D. Malali

Mechanical & Aerospace Engineering Theses & Dissertations

Designed for offshore deployment in irregular seas, the point absorber wave energy conversion (WEC) system is promisingly attractive amongst the currently available WEC technologies. The effectiveness of phase control when applied to a heaving point absorber through a hydraulic power take-off (PTO) system is systematically investigated in both regular and irregular waves. For this purpose, two phase control accumulators are utilized in the hydraulic PTO system. Simulations are performed in MATLAB® using the Cummins equation to model the dynamics of the heaving point absorber in the time domain.

For a given sea state, the opening instant of the control valves …

Dimensionless Criteria For Selecting Tidally-Influenced Advective-Dispersive Desalination Brine Mixing Plume Characterization Models, Alireza Shahvari

Civil & Environmental Engineering Theses & Dissertations

The very nature of requirements for implementing a desalination process is highly spatial due to the need to secure both a source for the operation and sink for brine dilution. Thus, the applicable coastal location is bound to natural tidal mixing characteristics and subjected to a near- or a far-field availability for source and sink. Mixing characteristics of coastal waters are very different from one point to another due to the spatiotemporal tidal characteristic in loco in a manner that it can vary from being highly advective to completely dispersive dominant. Once a location is identified, estimation of corresponding water …

The Modified Coastal Storm Impulse Parameter, Sayed Gholamreza Mahmoudpour

Civil & Environmental Engineering Theses & Dissertations

The correlation of the morphological changes to the coast and storm characteristics is among interests of coastal engineers. Better understandings of a storm's potential forces ultimately lead engineers to safer designs and minimize the damages. Therefore, a need to quantify the storm potential forces to a storm parameter is evident. The desired storm parameter is to consider all the relative physical factors and is to present realistic results that then can be proven by actual nature response.

The concept of Coastal Storm Impulse (COSI) parameter was first introduced by Basco and Klentzman (2006) and is based on the conservation of …

Evaluation Of Ocean-Energy Conversion Based On Linear Generator Concepts, Michael Allen Stelzer

Electrical & Computer Engineering Theses & Dissertations

A turbine generator is a device that converts mechanical rotation into electrical energy. Unfortunately, the primary driving force that has been used to provide this rotation has, thus far, been fossil fuels. Although fossil fuels have proven to be a reliable resource to continually supply the growing demand for electrical power, they are not without their financial and environmental drawbacks. With the continuously increasing demand for energy, it is hypothesized that the world may, in time, exhaust this precious natural resource and/or inflict permanent environmental damage upon our planet.

However, motions that occur in nature, such as ocean waves, can …

Methodology To Quantify Vertical Accelerations Of Planing Craft In Irregular Waves, Jennifer Suzanne Grimsley

Mechanical & Aerospace Engineering Theses & Dissertations

Planing craft operating in waves at high speeds can experience high, repetitive vertical accelerations that are random and nonlinear in relation to the sea condition. A proper understanding of vertical accelerations is critical to meet statistically based criteria for structural design, habitability, and equipment selection. Historically, it was assumed that planing craft vertical accelerations fit the Exponential distribution, and design methods adopted this conclusion. However, several published papers have raised doubts regarding the accuracy and validity of this Exponential distribution assumption.

The statistical behavior of planing craft vertical accelerations are examined for the Parent and Peak data sets from twenty-eight …

Towards The Efficient Probabilistic Characterization Of Tropical Cyclone-Generated Storm Surge Hazards Under Stationary And Nonstationary Conditions, Senanu Kudjo Agbley

Civil & Environmental Engineering Theses & Dissertations

The scarcity of observations at any single location confounds the probabilistic characterization of tropical cyclone-generated storm surge hazards using annual maxima and peaks-over-threshold methods. The EST and the JPM are indirect approaches aimed at estimating the probability distribution of the response variable of interest (i.e. storm surge) using the probability distributions of predictor variables (e.g. storm size, storm intensity etc.). In the first part of this work, the relative performance of the empirical simulation technique (EST; Borgman et al., 1992) and the joint probability method (JPM; Myers, 1970) is evaluated via stochastic simulation methods. It is shown that the JPM …

Passive And Active Nonlinear Control Of Ship Roll Motions Using U-Tube Tanks, Thongchai Phairoh

Mechanical & Aerospace Engineering Theses & Dissertations

A U-tube water tank is first designed to roll a ship floating on still water. The 6-degree of freedom (DOF) dynamic model of U-tube tank is derived and the effects of its parameters on ship roll motion are studied. Numerical simulations show that the U-tube tank is an effective stimulator to roll the ship on still water. For a rolling ship, the U-tube tank can be used as a damper to reduce ship roll motion quickly.

Active control of ship roll motion with a proportional and derivative (PD) controller, linear quadratic regulator (LQR), generalized predictive control (GPC), and deadbeat predictive …

Wind-Induced Exchange In Semi-Enclosed Basins, Rosario Sanay

OES Theses and Dissertations

The wind-induced circulation over laterally varying bathymetry was investigated in homogeneous and in stratified systems using the three-dimensional Regional Ocean Model (ROMS). For homogeneous systems, the focus was to describe the influence of the earth's rotation on the lateral distribution of the flow with particular emphasis on the transverse circulation. Along-basin wind-stress with no rotation caused a circulation dominated by an axially symmetric transverse structure consisting of downwind flow over the shoals and upwind flow in the channel along the whole domain. Transverse circulation was important only at the head of the system where the water sank and reversed direction …

Generalized Predictive Control Of Ship Coupling Motions Using Active Flume Tanks, Abdulkarim Mohammed Alotaiwi

Mechanical & Aerospace Engineering Theses & Dissertations

This dissertation uses the Generalized Predictive Control (GPC) approach to design a control system for a ship rolling motion coupled with the sway and yaw using an activated flume tank. GPC is a strategy based on system output prediction over finite horizon known as the prediction horizon. GPC controller is designed from the coefficients of the Autoregressive model with exogenous input (ARX) that are computed directly from input and output data. It computes the future control input based on the cost function with weighted input and output. System identification approach is implemented on the system to find the ARX coefficients …

Optimal Feedback Control For Ship Roll Motion Under Sea States, Anusit Anmanatarkul

Mechanical & Aerospace Engineering Theses & Dissertations

The primary influences of ship motion are roll motion. The purpose of this dissertation is to discuss a means to reduce the roll amplitude of ship motion in the case of zero forward speed using the roll mitigation device known as the flume tank, or U-tube, tank. Passive control and active control are studied. Optimal feedback control is the designated algorithm for activated roll mitigation device. The assumed model in this study is a submarine chaser. The linear coupled equation of swaying, rolling, and yawing motion of this assumed model is studied. The roll motion of this vessel is investigated …

Stratal Architecture In A Prograding Shoreface Deposit, Eastern Shore, Va: Relationship To Grain Size, Permeability, And Facies Distribution, Andrew C. Miller

OES Theses and Dissertations

A fundamental concern of the stratigrapher is to develop predictive models of stratigraphic organization. In sedimentology one of the most significant problems that has yet to be resolved is the fact that there is a lack of quantitative information regarding the relationship between geometry of beds, thickness of beds, grain size and sedimentary structures in sandy environments, especially shallow marine deposits. Scientists have also realized the need to correlate quantitative permeability to sedimentary structures and scales of stratigraphic organization. The purpose of the study is to investigate the scales of stratigraphic organization that control the variation of grain size and …

The Study Of Wave-Blocking And Current Effects On Nonlinear Interactions Of Shallow-Water Waves Using Advanced Boussinesq Models, Qin Chen

Civil & Environmental Engineering Theses & Dissertations

The first part of this work focuses on the derivation of enhanced Boussinesq-type equations for the combined motion of waves and currents in shallow water areas.

The strategy proposed in this work is to couple two known methods which are the sponge layer concept suitable for short waves and Sommerfeld radiation condition for currents. This coupling method provides satisfactory non-reflective boundaries for the simulation of fully coupled wave/current motion as demonstrated by the numerical experiments. We verify the model against the well known solutions based on the existing theories and good agreement has been observed. The numerical results confirm the …

Water Wave Refraction With Non-Linear Theory, Im Sang Oh

OES Theses and Dissertations

Two different kinds of wave refraction models are formulated in the present study using Stokes' third order wave theory. One type of model is utilized in a parametric study employing several different topographies. Wave trajectories obtained from this model, when obtained by using first and third order wave theory with and without the consideration of energy dissipation, show considerable differences. These differences are examined in more detail for a bottom of constant slope: (1) An approximate 10% difference occurs between the refraction coefficients obtained using the first and the third order wave theory. (2) Considerably different ray trajectories are detected …