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

Submerged Geosynthetic Reef as Shore Protection Measure for Islands

In general, the groyne sections are made of rubble stones of different sizes. To conserve the ecosystem and also due to the scarcity of natural rocks around certain locations, the reliance on these hard materials for the construction of groyne sections becomes questionable forcing us to look for alternate eco-friendly soft materials, for example, geo systems. In order to evaluate the feasibility and advantages of geo systems for groyne construction and to test their hydrodynamic stability, the core section of rubble stones was replaced by geo-bags filled with sand. The objective of this study is to assess the wave transmission, hydrodynamic stability and wave overtopping of a groyne section with a geo-bags filled core section through physical model studies. The tests were conducted in a wave flume in Department of Ocean Engineering, Indian Institute of Technology Madras, India. A model scale of 1:15 is adopted based on Froude’s scaling law and dimensional limitations of the testing facility. The aforementioned cross sections were tested simultaneously in a wave flume that was partitioned longitudinally. The transmission and hydrodynamic stability of both the sections have been analysed by subjecting the corresponding sections to the action of random waves defined by JONSWAP spectrum through a well-controlled experimental programme. The details of test set-up, testing facility, parameters of model, test procedure, analysis of results and discussion will be reported in this chapter.

Stability of Groynes Built Using Geo Systems

The measurement of tidal stream discharge is a complicated assignment in complex flow conditions that may be occasional or seasonal. The efficient discharge measurement in tidal streams is required with accurate real-time measurements over a longer-period. The discharge of tidal streams is computed as the product of the cross-sectional area and mean velocity. At present, the data on the discharge in tidal creeks and its behavior over time of the ingress of tide (i.e., rising or falling tide) which are seasonal along the Indian coast is inadequate, the understanding of which is considered in the present paper. This study has been carried out with the interest of exploring the seasonal flow pattern in the Kandla creek, Gulf of Kutch, Gujarat. The seasonal, temporal and spatial variation of Kandla Creek discharge of both vertical and lateral distributions of velocity was carried out by repetitive measurements by moving boat method throughout the 8 days of measurement during daylight of 10 to 12 hours a day. The magnitude and direction of the velocities relative to the boat were measured throughout the cross sections (east to west and/or west to east) at two locations (Location-1: North end of the Kandla creek and Location-2: South (near the creek mouth), by downward looking Acoustic Doppler Current Profiler (ADCP) equipment fixed at the side of the measurement vessel/boats with known draft and headings. The measurements were made at about 94 vertical traverses at each cross section. As soon as one traverse completion (left to right), the opposite side (right to left) of the creek traverse was measured for comparison. The maximum net discharge was recorded around 920 m3/sec at Location-1 and around 1900 m3/sec at Location-2, both during pre-monsoon with the ebb tide. During monsoon and post-monsoon season, the net discharge is observed during flood tide with relatively lesser magnitude than during the pre-monsoon ebb tide. The results on the discharge measurement confirm that the ebb tide is dominant during the pre-monsoon and the flood tide is dominant during the monsoon and post-monsoon seasons.

Seasonal Flow Characteristics of Kandla Creek Through In-Situ Measurements

Most of the fishing harbors along the Indian coast are located within the tidal inlets, barring a few on the open coast. Fishing harbor on an open coast needs protection in the form of breakwaters or training walls for providing tranquility conditions and safe vessel maneuvering and landing facilities. Practically, all inland fishing harbors suffer siltation problems. The studies on the development of a new inland fishing harbor on River Chapora (15° 36′4 6.22″ N and 73° 44′ 51.34″ E) in the state of Goa in India with such problem were carried out, the results of which are reported in this paper.

Design of a Minor Fishing Harbor in India with Special Reference to Training of the Mouth of River Chapora

Marine renewable energy has potential benefits like the enhancement of the livelihood and can solve the energy-security. For cost-effective solution, a multipurpose wave energy system with an integration into coastal protection has been explored in detail. Having evaluated the performance of an OWC in isolation in the previous chapters, an effort is made to understand the performance of the combination of wave energy technology with detached offshore breakwaters. The said multi-purpose option, termed as OWCBW system is investigated for optimizing the spacing between an array of OWC devices subjected to regular and random waves in normal and oblique wave incidences. It is observed that the OWCBW system with thrice the width of the model spacing exhibited a better performance. The OWC system is found to absorb more power when being placed in an array of devices than compared to an isolated device. The extent of decrease in relative capture width at the resonant frequency of the system for oblique wave incidence compared to that of normal wave incidence is found to be about 30%.

Vallam Sundar

Papers

Submerged Geosynthetic Reef as Shore Protection Measure for Islands

Stability of Groynes Built Using Geo Systems

Seasonal Flow Characteristics of Kandla Creek Through In-Situ Measurements

Design of a Minor Fishing Harbor in India with Special Reference to Training of the Mouth of River Chapora

Hydrodynamic Performance of an Array of OWC Devices Integrated with Breakwater