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 research over several decades on the Oscillating Water Column has been on the enhancement of its efficiency by optimizing its configuration and its wave power absorption. However, the stability of such a device is of great concern, which requires a detailed evaluation of wave induced loadings on such structures. This chapter details a comprehensive experimental investigation to understand the dynamic pressures on the different components of the OWC including the total force on the structure induced by both regular and random waves. The design of the lip wall of OWC is dictated by the seaward exerted pressure it experiences, which is a critical parameter, as it governs the stability of the structure towards the seaside. The total horizontal wave force is noted to be 2.5 to 3 times the total vertical wave force. The pressures on the rear wall of the OWC chamber and the air pressure over the roof of the caisson exhibit a reverse trend in their variation compared to the pressures on the front of the lip wall. A comparison of the measured force with the formula of (Goda Y Random seas and design of maritime structures. University of Tokyo press (1985)) has revealed that the formula overestimates the shoreward force and underestimates the seaward force in the low frequency zone.

Wave Induced Pressures and Forces on an OWC Device

Impact of coastal structure on shorelines along the southeast and southwest coasts of india

The formation of shoals, leading to a reduction in the required depth for navigation, is a perennial problem in approach channels of harbours and estuaries. Likewise, this is a major obstacle to the navigation of larger vessels to the study area reported in this paper . A field study on Kandla creek estuary was conducted to assess the flow and sediment dynamics inside the creek where one of the major ports of India, Deendayal Port, is located. In-situ water and sediment sampling and discharge measurements were carried out for the pre-monsoon, end of the monsoon and post-monsoon seasons in 2019–2020. Further, the grain size analysis and total suspended sediment analysis were done from the collected samples. The results highlight the domination of strong ebb currents in pre-monsoon and flood currents at the end of the monsoon and post-monsoon in the creek, which influences the sediment transport proportionately. The present paper reports the sediment characteristics and the estimated net sediment transport through measurements along with flow characteristics in Kandla creek. The field data presented here will support the researchers in the numerical modeling and validation of hydrodynamics and morphodynamics in the estuaries. 

Field investigation of suspended sediment transport study in the Kandla creek, Gujarat, India

Extreme wave environments have an effect on all marine engineering applications. Hence, the estimation of extreme wave conditions is a prerequisite for offshore and coastal developments like the optimization of marine energy converters, design of port and harbor infrastructures, flood risk analysis and management, and planning of beach management schemes. Given this. extreme wave maps are developed for the Indian territorial waters using the Generalized Extreme Value distribution method. ERA-interim wave hindcast data for 36 years are utilized for this analysis obtained from the European Centre for Medium-Range Weather Forecasts (ECMWF) global atmospheric reanalysis. However, the oceans are highly dynamic, with the wave climate and sea states varying in both space and time. These extreme wave maps may aid as a quick guide in identifying regions of extreme wave heights lying within the design structural criteria of the marine structures to be constructed.

Development of Extreme Wave Maps for Indian Territorial Waters

Large floating multi-purpose platforms are interesting and emerging concepts in terms of envisaged future development in the offshore engineering. The investigation on the hydrodynamic behaviour of such structures plays an important role in their characterization. In particular, vibration control and motion reduction of the platform may be crucial for its operation since most of the renewable energy converters cannot cater to large support motions (e.g. wind turbines, photovoltaic plants and OWC wave energy converters). With this as the background, a small-scale open-sea experimental investigation on a barge structure has been carried out in the Natural Ocean Engineering Laboratory (NOEL) in Reggio Calabria, Italy. The barge was equipped with removable vertical plates in order to investigate their effects on the structure dynamics and their optimal configuration, in terms of its motion attenuation. In addition, a numerical model using the commercial software Ansys AQWA (v. 16.1) is used to investigate its dynamic effects for five different configurations of the plates both in the time and in the frequency domains.

Vallam Sundar

Papers

Wave Induced Pressures and Forces on an OWC Device

Impact of coastal structure on shorelines along the southeast and southwest coasts of india

Field investigation of suspended sediment transport study in the Kandla creek, Gujarat, India

Development of Extreme Wave Maps for Indian Territorial Waters

Vibration Control of Large Floating Offshore Structures by Means of Damping Plates: A Case Study