Nonlinear Oscillations: Exact Solutions and their Approximations

Kumaraswamy [Generalized probability density-function for double-bounded random-processes, J. Hydrol. 462 (1980), pp. 79–88] introduced a distribution for double-bounded random processes with hydrological applications. For the first time, based on this distribution, we describe a new family of generalized distributions (denoted with the prefix ‘Kw’) to extend the normal, Weibull, gamma, Gumbel, inverse Gaussian distributions, among several well-known distributions. Some special distributions in the new family such as the Kw-normal, Kw-Weibull, Kw-gamma, Kw-Gumbel and Kw-inverse Gaussian distribution are discussed. We express the ordinary moments of any Kw generalized distribution as linear functions of probability weighted moments (PWMs) of the parent distribution. We also obtain the ordinary moments of order statistics as functions of PWMs of the baseline distribution. We use the method of maximum likelihood to fit the distributions in the new class and illustrate the potentiality of the new model with a...

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A new family of generalized distributions

Wind speeds over the world’s oceans have increased over the past two decades, as have wave heights. Studies of climate change typically consider measurements or predictions of temperature over extended periods of time. Climate, however, is much more than temperature. Over the oceans, changes in wind speed and the surface gravity waves generated by such winds play an important role. We used a 23-year database of calibrated and validated satellite altimeter measurements to investigate global changes in oceanic wind speed and wave height over this period. We find a general global trend of increasing values of wind speed and, to a lesser degree, wave height, over this period. The rate of increase is greater for extreme events as compared to the mean condition.

https://researchbank.swinburne.edu.au/file/bca43746-6f16-4ad2-a4b7-27f8d8d60fed/1/PDF (Published version).pdf

Global trends in wind speed and wave height over the past 25 years

Evolution of Design Method Against Random Waves Statistical Properties and Spectral of Sea Waves Transformation and Deformation of Random Sea Waves Design of Breakwaters Design of Coastal Dikes and Seawalls Probabilistic Design of Harbor Facilities Harbor Tranquility and Vessel Mooring Hydraulic Model Tests with Random Waves Theoretical Description of Random Sea Waves Statistical Theory of Irregular Waves Techniques of Random Wave Analysis 2D Computation of Wave Transformation with Random Breaking and Nearshore Currents Statistical Analysis of Extreme Waves Prediction and Control of Beach Deformation Processes.

Random seas and design of maritime structures

The interaction of waves with obstacles is an everyday phenomenon in science and engineering, arising for example in acoustics, electromagnetism, seismology and hydrodynamics. The mathematical theory and technology needed to understand the phenomenon is known as multiple scattering, and this book is the first devoted to the subject. The author covers a variety of techniques, describing first the single-obstacle methods and then extending them to the multiple-obstacle case. A key ingredient in many of these extensions is an appropriate addition theorem: a coherent, thorough exposition of these theorems is given, and computational and numerical issues around them are explored. The application of these methods to different types of problems is also explained; in particular, sound waves, electromagnetic radiation, waves in solids and water waves. A comprehensive bibliography of some 1400 items rounds off the book, which will be an essential reference on the topic for applied mathematicians, physicists and engineers.

Multiple Scattering: Interaction of Time-Harmonic Waves with N Obstacles

The wave reflection and transformation characteristics of partially submerged slotted screens, consisting of horizontal wave intercepting elements, have been studied using the Green’s Identity formula. The effects of the relative depth of submergence of the wave screen on its hydrodynamic performance characteristics under the action of regular and random waves are investigated through numerical and experimental studies. The comparisons of reflection, transmission coefficients as well as the dynamic pressures exerted on the individual wave screen elements from experiments with numerical results are found to be in close agreement. The details of the numerical method, physical model, hydrodynamic testing facility, experimental setup, procedure and analysis along with the interpretation of results are presented and discussed in this paper. A screen height below the water level of 0.3d, where d is the water depth, is found to be an optimal system.

Reflection and transmission characteristics of partially submerged slotted wave screens

In this article, tsunamis represented as solitary waves was simulated using the fully nonlinear free surface waves based on Finite Element method developed by Sriram et al. (2006). The split up of solitary wave while it propagates over the uneven bottom topography is successfully established. Wave transmission and reflection over a vertical step introduced in the bottom topography is in good agreement with the experimental results from Seabra-Santos et al. (1987). The wave transformation over a continental shelf with different smooth slopes reveals that the solitary wave reflection increases while the continental slope varies from flat to steep. The interaction of the solitary wave with a vertical wall for different wave steepness has been analysed. The reflected shape of the profile is in good agreement with the observation made by Fenton and Rienecker (1982) and an increase in wave celerity is observed.

NWF: Propagation of Tsunami and its Interaction with Continental Shelf and Vertical Wall

Pressures and Forces on an Oscillating Water Column–Type Wave Energy Caisson Breakwater

The submerged semicircular breakwater (SBW) is mainly adopted to prevent beach erosion and to reduce the incident wave energy on its leeside, if it is used in front of a vertical breakwater. In addition, it facilitates the premature wave breaking, which in turn causes the reduction in wave energy. The dynamic pressures and forces exerted on the submerged SBW with 7%, 11 %, and 17% of the exposed surface area with perforations on its seaside due to regular waves were measured. The hydrodynamic characteristics such as variations in the dimensionless pressures and forces, reflection and transmission coefficients on the semicircular caisson as a function of scattering parameter for three different water depths are presented and an optimum depth of submergence is arrived. The results on the above stated variables for seaside perforated SBWs are compared with the results of an impermeable SBW to study the effect of perforations.

Regular Wave Measurements on a Submerged Semicircular Breakwater

The hydrodynamic interaction of regular and random waves with a model offshore deck has been investigated in a wave flume. The hydrodynamic pressures and forces on the model as well as its reflection and transmission characteristics are investigated in a dimensionless form. The experiments were carried out for three different clearances (e) between the still water level and the subface of the model. In order to investigate the effects of relative clearance of the deck ( e/H in case of regular waves and e/ Hs in case of random waves), different wave steepnesses ( H/L in case of regular waves and Hs / Lp in case of random waves) were employed by varying wave height (H) and wavelength (L) . The effects of the wave steepness, relative clearance of the deck, relative length of the model ( B/L in case of regular waves and B/ Lp in case of random waves) on the pressures and forces on the deck slab are investigated with a well controlled experimental program. The variation of the pressures along the length of the...

Vallam Sundar

Papers

Reflection and transmission characteristics of partially submerged slotted wave screens

NWF: Propagation of Tsunami and its Interaction with Continental Shelf and Vertical Wall

Pressures and Forces on an Oscillating Water Column–Type Wave Energy Caisson Breakwater

Regular Wave Measurements on a Submerged Semicircular Breakwater

Wave-Induced Pressures and Forces on Deck Slabs near the Free Surface