Vallam Sundar

Bio: Vallam Sundar is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Wind wave & Shore. The author has an hindex of 24, co-authored 195 publications receiving 1778 citations. Previous affiliations of Vallam Sundar include Indian Institutes of Technology.

Integrated Solution For Coastal Protection And Wave Energy Extraction

Abstract: A detailed three-dimensional laboratory investigation on hydrodynamic performance of an array of oscillating water column (OWC) devices, combined with offshore detached breakwater (ODBW) subjected to oblique wave incidence was studied. A Froude scale of 1:20 was chosen for integrating five similar devices of OWC to the ODBW (OWCBW) and a series of experiments was carried out in a shallow wave basin for angle of wave approaching between 900 and 700 with reference to the front face of the structure with an angular decrement of 100. The hydrodynamic performance was studied in terms of front wall outside pressure, wave amplification, air pressure, capture width, and relative capture width. The convergence of water waves due to three-dimensional effects concentrates high amount of energy in front of the array of OWCs for normal wave incidence. It makes a system to absorb larger amount of wave power of about 1.12 times of the given input power at the natural frequency of the system. This confirms that the array of OWC devices, exhibits better performance than in isolation. The performance of the system reduces with angular decrement due to peak of the wave front reaches the line front of OWCBW in different time along with wave dissipation over the breakwater. The natural frequency of the system was found to be lying in the vicinity of d/L p of 0.12 and unaltered for different angles of wave incidence.

Congregation of particles on a plane boundary due to the flow induced by an oscillating sphere

Abstract: The complex flow field associated with a spherical structure oscillating adjacent to a solid boundary is significant in ocean engineering. The dynamic interaction between the flow induced by an oscillating sphere and the boundary is evident not only in terms of flow-field deformation around the structures but also on the boundary in the form of shear stress modifications. The present study aims to understand the influence of a plane boundary on the shear stress distributions and particle motion near the boundary induced by the flow due to a submerged sphere oscillating in a viscous fluid. Experiments are conducted using a non-intrusive flow visualization technique and three-dimensional Direct Numerical Simulations are used to link the time-mean results of the experiments to the simulated Lagrangian particle drift on the plane boundary. The dye tracer in the experiments and the Lagrangian particles in the simulation congregate at the same location. This stagnation location coincides with a ring of zero mean shear stress centered on the point on the plane boundary through which the axis of oscillation of the sphere passes. This ring of zero mean stress is termed the congregation zone. The radius of the particle congregation zone is investigated as a function of the sphere oscillating amplitude, Reynolds number, and the distance between the center of the sphere and the plane boundary. Further, a systematic power scaling law is established for the radius of the congregation zone from the control parameters.

A new family of generalized distributions

Abstract: 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...

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

Abstract: 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.

Random seas and design of maritime structures

Abstract: 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.

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

Abstract: 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.