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 coastal and offshore structures are some times exposed to group of waves with successive higher wave elevations exceeding the significant wave height, which is considered to be vulnerable for the stability of the structures. Hence, the knowledge on the existence and frequency of occurrence of ocean wave groups at a particular region of interest is important for the design of the ocean structures. In the present study, the wave groups were simulated theoretically and the same was generated in the laboratory wave flume. The measured wave elevations were analysed through statistical, spectral and wavelet approaches to detect the existence of the groupiness.Copyright © 2006 by ASME

Laboratory Simulation and Analysis of Wave Groups

The east coast of the Indian Peninsula experiences the effects of a devastating cyclone at least annually. The Thane cyclone of 29–30 December 2011 has been once such event that resulted in significant damages along the coastline of Tamil Nadu on the southeast coast of India (13° 9′ 10′ N and 80° 21′E). Waves as high as 8–12 m in a water depth of 20 m have been measured. Such huge waves, combined with a storm surge of 0.5 m, lead to severe damages to coastal structures during the passage of the cyclone. As a part of an exercise in assessing the sediment transport rates through measurements of the hydrodynamic driving parameters along the coast of major port of Chennai instruments were deployed for the measurement of waves and flow field. The measurement campaign was carried out at a location of about 120 km north of the cyclone made landfall. The ENCEP wind data formed the input for executing the WAM model for the simulation of wave characteristics, which are compared with the measured wave data. The agre...

Investigation on the Cyclonic Seastate along Southeast Coast of India

Hooghly estuary is a complex dynamic estuary facing dredging maintenance and navigation-related problems due to the high rate of sediment load brought by the Hooghly River. The present study is to investigate the hydrodynamics and morphodynamics of the Hooghly estuary, with specific reference to stability of Eden navigational fairway and permanent operation of the channel as a possible main navigational route to HDC in the place of Auckland channel from the Bay of Bengal. Impact of stoppage of dredging at Auckland bar on the other channels (Eden and the Rangafalla channel that connect to Kolkata Dock System, KDS) is investigated. Simulations involving different scenarios like Auckland channel dredged and non-dredged conditions are considered to investigate the stability of the Eden channel and also to address the aspects relating to the maintenance of other channels. In the study, for the Auckland open condition, the predicted siltation levels are of about 8–12 cm over Auckland and about 4–8 cm over Eden bar, over 15 days of simulation. For Auckland closed condition and for Auckland with two tracks, the results indicate a marginal reduction in siltation over the entire Eden area, and it is also observed that the siltation in Jellingham and Haldi River confluence is significantly reduced. For the monsoon conditions in all the above scenarios, the results, as per the siltation patterns and as per the siltation levels on the edges of the channels, indicate that there will be a marginal increase in siltation, by about 20% when higher silt load is considered. The study suggests that Eden channel could continuously be used with little dredging in the longer term of more than 5 years with monitoring and realignment of the channel to cater for movement of sandbars. Further, non-dredging of Auckland channel may not have any bearing on the operation of Eden, Jellingham and Rangafalla channels.

Study on Stability of Eden Navigational Channel in Hooghly River Estuary

Vegetation along a coastline could offer significant protection of the adjoining land area against natural hazards such as storm surge and tsunami. In this context, the flexibility of the individual that stems within the green belt is understood to play an important role in the attenuation of momentum of the incoming waves. The physics of which, is yet to be understood completely. Difficulty in modeling the rigidity of the plantations, both numerically and experimentally, is the main cause for this lack of understanding. In the present work, a detailed laboratory study is taken up to examine the resistance characteristics of a group of model slender flexible cylinders. The individual cylinders of the group were fixed to the bed in a staggered configuration. The size, vegetation density and the elastic modulus of the individual stems were chosen such that the tests covered the practical ranges of vegetation in coastal forestry. The Manning's n for different flow conditions as well as for vegetative parameters was obtained from the physical tests in uniform steady current. The results clearly bring out the variation of flow resistance in terms of flow velocity, density of plantation, individual stem diameter and its elastic property. A new empirical relationship is proposed for estimation of Manning's n for staggered flexible emerging plantations which is valid for depths of flow greater than 0.8 times the undeflected plant height.

MANNING'S 'n' FOR STAGGERED FLEXIBLE EMERGENT VEGETATION

This paper presents the results from a comprehensive experimental study on the Quadrant Face Pile Supported Breakwater (QPSB) in two different water depths exposed to three different oblique wave a...

Vallam Sundar

Papers

Laboratory Simulation and Analysis of Wave Groups

Investigation on the Cyclonic Seastate along Southeast Coast of India

Study on Stability of Eden Navigational Channel in Hooghly River Estuary

MANNING'S 'n' FOR STAGGERED FLEXIBLE EMERGENT VEGETATION

Hydrodynamic characteristics of vertical and quadrant face pile supported breakwater under oblique waves