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.

Impact of Flow-Driven Debris on Coastal Structure During Tsunami Bore

Abstract: Tsunami impact on infrastructure along the coast causes severe destruction, loss of human lives and negative influence on the economy. When tsunami propagates towards the coastline, the flow often resembles a bore which propagates with a high velocity and takes everything on its way, including heavy objects. When reaching the structure, this water-driven debris induces a kind of impact force and magnifies the load on structures along the coast. The present study is aimed to measure the load of tsunami-borne debris on a building constructed near the shoreline. In many situations, tsunami or any flood nearshore resembles a surge caused by a dam-break event; therefore, to model this process, we conducted our experiments by setting up a dam-break arrangement in a wave flume of 72.5 m length, 2 m wide and 2.5 m deep at the Department of Ocean Engineering, IIT Madras, India. A Froude scale of 1:20 was adopted for modelling the coastal structure and the debris placed over a beach slope of 1:30. The hydraulic bore was generated by a sudden opening of the gate of the tank. We considered three water depths of 0.8, 0.9 and 1.0 m. The debris was modelled as a box-shaped structure weighing 4.2, 5.6 and 6.0 kg. A video camera was used to capture the surging of the hydraulic bore and to study the character of debris motion during impact. The impact forces acting on the structure due to debris were measured with a load cell. The acquired data were further analysed and discussed.

Shore Protection for a Placer Deposit Rich Beach of the Southwest Coast of India

Abstract: The placer deposits dominated Neendakara-Kayamkulam sector along the Kerala coast on the southwest coast of India may be characterized as a dynamic, unstable beach based on shoreline oscillations observed over the past years. Both long-term and short-term shoreline variations can be easily linked directly to a number of factors - both natural and anthropogenic. Of these, activities such as large scale mining for heavy minerals; dredging and construction of hard structures such as breakwaters and groins; have contributed significantly to the changes in shoreline. The coastal hydrodynamics of the area is highly complex because of the variation in shoreline orientation and near shore slope. The present work is an attempt to understand the coastal processes and to identify the factors responsible for the shoreline oscillations by conducting numerical model studies. The studies on the shoreline changes are also carried out as a part of this study in order to identify the critical areas of the shore that need i...

Distribution of Longshore Currents and Sediment Transport Rates in the Surf Zone Off Paradeep, India

Abstract: The distributions of longshore current velocities and sediment transport rates across the width of the surf zone off Paradeep Port have been evaluated using the model developed by Komar(1). Monthly distribution of longshore current velocities and associated sediment transport rates are presented. Distribution of sediment transport rates are evaluated upto the breaker zone while those of longshore current velocities extend even beyond it. Longshore current velocities are strongest and sediment transport rates are highest in August while weak currents and low transport are observed in October. A comparison of monthly sediment transport rates as obtained by the model and the monthly net sediment transport rates computed using CERC (2) formula shows a close correlation between the two values.

Stability of a micro-tidal inlet using semi-numerical approach:

Abstract: Tidal inlets get disconnected depending on the seasons due to the formation of sand bars near its mouth are termed as “seasonally open tidal inlets.” These inlets are usually small of width of about 100 m and occur in micro-tide (tidal range not exceeding 1 m). Since the east coast of India experiences a net littoral drift of up to about 0.8 Mm3/annum, which is one of the largest in magnitudes that needs to be considered in the analysis of modeling of the sand bar formation and the associated phenomena. Kondurpalem inlet situated along the South east coast of India is considered as a case study. A frequency domain wave model (STeady-state spectral WAVE) has been used to compute the nearshore wave climate. The wave-induced currents have been obtained, and the longshore sediment transport rate is obtained through empirical relations. The tidal prism is found from measured depth and tidal velocity by solving shallow water equations. The stability of the inlet is investigated by applying the criteria develope...

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.