Modeling Nonlinear Stochastic Ocean Loads as Diffusive Stochastic Differential Equations to Derive the Dynamic Responses of Offshore Wind Turbines
Modeling Nonlinear Stochastic Ocean Loads as Diffusive Stochastic Differential Equations to Derive the Dynamic Responses of Offshore Wind Turbines

Author: David F. H. Larson

Publisher:

Published: 2016

Total Pages: 54

ISBN-13:

DOWNLOAD EBOOK

A procedure is developed for modeling stochastic ocean wave and wind loads as diffusive stochastic differential equations (SDE) in a state space form to derive the response statistics of offshore structures, specifically wind turbines. Often, severe wind and wave systems are highly nonlinear and thus treatment as linear systems is not applicable, leading to computationally expensive Monte Carlo simulations. Using Stratonovich-form diffusive stochastic differential equations, both linear and nonlinear components of the wind thrust can be modeled as 2 state SDE. These processes can be superposed with both the linear and nonlinear (inertial and viscous) wave forces, also modeled as a multi-dimensional state space SDE. Furthermore, upon implementing the ESPRIT algorithm to fit the autocorrelation function of any real sea state spectrum, a simple 2-state space model can be derived to completely describe the wave forces. The resulting compound state-space SDE model forms the input to a multi-dimension state-space Fokker-Planck equation, governing the dynamical response of the wind turbine structure. Its solution yields response, fatigue and failure statistics-information critical to the design of any offshore structure. The resulting Fokker-Planck equation can be solved using existing numerical schemes.

Stochastically Excited Nonlinear Ocean Structures
Stochastically Excited Nonlinear Ocean Structures

Author: Michael F. Shlesinger

Publisher: World Scientific

Published: 1998

Total Pages: 340

ISBN-13: 9789810233921

DOWNLOAD EBOOK

Ocean structures, including ships, boats, piers, docks, rigs and platforms, are subject to fair weather wind and waves, as well as violent storms. A scientific analysis of these structures, under varying conditions, requires a mix of civil engineering, physics and applied mathematics. Chapters by experts in these fields are presented which explore the nonlinear responses of ocean structures to stochastic forcing. Theoretical methods calculate aspects of time, frequency and phase space responses. Probabilities governed by stochastic differential equations arc investigated directly or through moment correlations, such as power spectra. Calculations can also involve level crossing statistics and first passage times. Tiffs book will help scientists study stochastic nonlinear equations and help engineers design for short term survivability of structures in storms and long life in the face of everyday fatigue.

Stochastic Modelling in Physical Oceanography
Stochastic Modelling in Physical Oceanography

Author: Robert Adler

Publisher: Springer Science & Business Media

Published: 2012-12-06

Total Pages: 473

ISBN-13: 1461224306

DOWNLOAD EBOOK

The study of the ocean is almost as old as the history of mankind itself. When the first seafarers set out in their primitive ships they had to understand, as best they could, tides and currents, eddies and vortices, for lack of understanding often led to loss of live. These primitive oceanographers were, of course, primarily statisticians. They collected what empirical data they could, and passed it down, ini tially by word of mouth, to their descendants. Data collection continued throughout the millenia, and although data bases became larger, more re liable, and better codified, it was not really until surprisingly recently that mankind began to try to understand the physics behind these data, and, shortly afterwards, to attempt to model it. The basic modelling tool of physical oceanography is, today, the partial differential equation. Somehow, we all 'know" that if only we could find the right set of equations, with the right initial and boundary conditions, then we could solve the mysteries of ocean dynamics once and for all.

Stochastic Dynamics of Marine Structures
Stochastic Dynamics of Marine Structures

Author: Arvid Naess

Publisher: Cambridge University Press

Published: 2013

Total Pages: 425

ISBN-13: 0521881552

DOWNLOAD EBOOK

For students and professionals, this covers theory and methods for stochastic modelling and analysis of marine structures under environmental loads.

Wave Loads on Offshore Wind Turbines
Wave Loads on Offshore Wind Turbines

Author:

Publisher:

Published: 2015

Total Pages: 65

ISBN-13:

DOWNLOAD EBOOK

Ocean energy is one of the most important sources of alternative energy and offshore floating wind turbines are considered viable and economical means of harnessing ocean energy. The accurate prediction of nonlinear hydrodynamic wave loads and the resulting nonlinear motion and tether tension is of crucial importance in the design of floating wind turbines. A new theoretical framework is presented for analyzing hydrodynamic forces on floating bodies which is potentially applicable in a wide range of problems in ocean engineering. The total fluid force acting on a floating body is obtained by the time rate of change of the impulse of the velocity potential flow around the body. This new model called Fluid Impulse Theory is used to address the nonlinear hydrodynamic wave loads and the resulting nonlinear responses of floating wind turbine for various wave conditions in a highly efficient and robust manner in time domain. A three-dimensional time domain hydrodynamic wave-body interaction computational solver is developed in the frame work of a boundary element method based on the transient free-surface Green-function. By applying a numerical treatment that takes the free-surface boundary conditions linearized at the incident wave surface and takes the body boundary condition satisfied on the instantaneous underwater surface of the moving body, it simulates a potential flow in conjunction with the Fluid Impulse Theory for nonlinear wave-body interaction problems of large amplitude waves and motions in time domain. Several results are presented from the application of the Fluid Impulse Theory to the extreme and fatigue wave load model: the time domain analysis of nonlinear dynamic response of floating wind turbine for extreme wave events and the time domain analysis of nonlinear wave load for an irregular sea state followed by a power spectral density analysis.

Numerical Modeling of Ocean Dynamics
Numerical Modeling of Ocean Dynamics

Author: Zygmunt Kowalik

Publisher: World Scientific

Published: 1993

Total Pages: 508

ISBN-13: 9789810213336

DOWNLOAD EBOOK

While there are several excellent books dealing with numerical analysis and analytical theory, one has to practically sift through hundreds of references. This monograph is an attempt to partly rectify this situation. It aims to introduce the application of finite-difference methods to ocean dynamics as well as review other complex methods. Systematically presented, the monograph first gives a detailed account of the basics and then go on to discuss the various applications. Recognising the impossibility of covering the entire field of ocean dynamics, the writers have chosen to focus on transport equations (diffusion and advection), shallow water phenomena ? tides, storm surges and tsunamis, three-dimensional time dependent oceanic motion, natural oscillations, and steady state phenomena. The many aspects covered by this book makes it an indispensable handbook and reference source to both professionals and students of this field.