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

An experimental study has been carried out to assess the sloshing pressure expected on the side walls of the tank and on top panel. A liquid fill level with an aspect ratio (hs /l, where hs is the static liquid depth and l is the tank length) of 0.488 is considered which corresponds to 75% liquid fill level. In view of suppressing sloshing oscillation and consequent sloshing pressure, the baffle wall configurations such as porous wall at l/2 and porous walls at l/3 and 2l/3 were adopted. Three porosities of 15%, 20.2%, and 25.2% were considered. The sloshing tank is fitted into the freely floating barge of model scale 1:43. The barge is kept inside the wave flume in the beam sea conditions. The effects of wave excitation frequencies and on the sloshing pressure variation have been studied in detail. For comparison purpose, solid wall placed at l/2 (Nasar and Sannasiraj, 2018) is also considered and, the salient results are herein reported.

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Effect of porous baffle on sloshing pressure distribution in a barge mounted container subjected to regular wave excitation

Typically, the dimensions of OWC chamber have a single resonant frequency which captures efficiently wave energy over a narrow range of frequency of the waves. The high-frequency waves are reflected. Provision of a pair of additional harbour walls in front of the device creates an added resonance enabling it to capture substantial energy from a wider range of frequency of the waves. Although, there exists a substantial loss in energy due to wave deformation as the wave from the offshore approach shallow waters, in which case, the harbour walls prevent any further dissipation till it reaches the device. This chapter reports the influence of harbour walls on the hydrodynamic characteristics of a bottom - mounted OWC. The study was carried out with different configurations of harbour walls, i.e., the projecting length was varied in terms of the ratio of harbour wall length (c) to the breadth of OWC (b), (c/b = 1, 1.5 and 2). The opening angle of harbour wall was varied in the range of [π/2, 7π/8] in an interval of π/8 with respect to the front lip wall of OWC. The results reveal that the efficiency of the OWC with the harbour walls has been significantly improved. The details of such a behaviour are herein discussed.

Performance Characteristics of an OWC in Regular and Random Waves

A numerical investigation has been carried out to obtain a non-dimensional grid size (grid size/ tsunami base width) for the near shore discretisation of computational domains for long wave modelling. A 1D domain has been considered in which, the flow has been solved by 1D shallow water equations with vertically integrated flow variables. The sensitivity study of the grid size was carried out in the 1D channel with an open boundary at one end and shelf boundary at the other end. The grid size was varied from 10 m to 1000 m and its effect on the computation of the tsunami run-up along the shoreline has been investigated. The non-dimensional grid size for the computation of run-up was optimised by comparing the non-dimensional run-up (tsunami run-up/initial tsunami height) and a threshold value of 5.0e-4 was obtained. Further, the study was extended to real scenario by adopting various grids for the shelf region of northern Tamil Nadu coast, south east coast of India in 2D and a suitable grid size was obtained.

Identification of Suitable Grid Size for Accurate Computation of Run-up Height

Wave climate in a groin field

The dynamic pressures exerted on a vertical wall due to cnoidal waves have been investigated in presence and absence of model vegetation on its seaside. The pressures were measured at 3 different elevations along the wall. Tests were conducted with waves of constant height of 0.11m, with its period was varying between 5 and 20secs, thus covering a wide range of Ursell parameter varying between 18 and 700. The model vegetation was positioned adjacent to the wall on its seaside. All the vegetal characteristics including their rigidity are carefully modelled. The peak pressures (pmax) were extracted from the measured time series and are presented in a dimensionless form as a function of parameters governing the characteristics of waves and plantation. Two types of configurations of the green belt with the individual stems of vegetation fixed in tandem and staggered arrangement were considered for the tests. The study indicates that the staggered arrangement of plantation is more effective in attenuating the ...

https://journals.sagepub.com/doi/pdf/10.1260/1759-3131.2.3.169

Vallam Sundar

Papers

Effect of porous baffle on sloshing pressure distribution in a barge mounted container subjected to regular wave excitation

Performance Characteristics of an OWC in Regular and Random Waves

Identification of Suitable Grid Size for Accurate Computation of Run-up Height

Wave climate in a groin field

Role of Vegetal Configuration on the Pressures Due to Cnoidal Waves on a Wall