Showing papers by "Vallam Sundar published in 2013"

Wind-Wave Characteristics and Climate Variability in the Indian Ocean Region Using Altimeter Data

Abstract: The significant wave height and wind speed derived for the period 1993–2010 from altimeter data sets over the Arabian Sea, Bay of Bengal, and the Indian Ocean categorized as six zones has been analyzed. The average variation of both significant wave height and wind speed is found to be almost stable for the period of study. The study reveals that the average wind speed increases by about 6cm/sec/year during monsoon and post monsoon in the southern Indian Ocean. The distribution of wind and waves was studied in the context of seasonal variations. In addition, the average inter-annual and intra-annual variations along with the statistical parameters such as standard deviation, and root mean square wave height for the six zones are also reported in this paper.

Artificial Reefs: A Review

Abstract: A comprehensive literature review on the material characteristics, design of size and shape, application and management of artificial reef has been carried out. Multipurpose Artificial Surfing Reefs (MPASR) are increasingly being adopted for coastal protection because of several advantages associated with them such as coastal protection by reducing the wave energy, recreation of beaches (surfing, fishing, and diving), habitat for marine organisms and increase in socioeconomic prosperity. The most important characteristic is that they are soft barriers. It is concluded that although artificial reefs do have the ability to fulfill many objectives, for which they are meant, their success will depend mainly on the quality of planning and management prior to their implementation.

Wave Interaction with a Double Chamber Oscillating Water Column Device

Abstract: The principle of oscillating water column within a chamber due to the propagating oscillatory ocean waves being converted into clean energy through wave energy convertor referred to as Oscillating water column (OWC) device is a well proven concept that still remains as one of the most promising alternate sources of energy from the Ocean. The OWC has single column of water oscillation, whereas, Double Chamber Oscillating Water Column (DCOWC) has two chambers of water oscillation. DCOWC is relatively a new concept. In this paper, the performance characteristics of a DCOWC is evaluated through a well-controlled experimental investigation in a wave flume. The conceptual design aspect of DCOWC and its uniqueness compared with the present state of art in wave energy converters (WECs) are explained. The efficiency of the system is assessed by considering the variations in the geometrical dimensions of the system along with the different characteristics of incident waves. The methodology adopted for evaluating th...

MANNING'S 'n' FOR STAGGERED FLEXIBLE EMERGENT VEGETATION

Abstract: 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.

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...

Wave Overtopping Over Crown Walls and Run-up on Rubble Mound Breakwaters with Kolos Armour under Random Waves

Abstract: The design of rubble mound structures like breakwaters and seawalls are influenced by the wave run-up and overtopping over them. The above phenomena largely depend on the type of the armour units as they directly interact with the incident waves. The hydrodynamic characteristics of various concrete armour units have been established by several researchers. A new armour block, ‘Kolos’, a modified version of Dolos, is considered in this study for a detailed investigation. An attempt is made to establish empirical relationships for the estimation of wave overtopping discharges over crown wall and run-up on Kolosarmoured slope exposed to random wave from the results of a comprehensive experimental program. Further, the results are compared with that of a tested section with natural rocks as armour layer and with that of other investigators.

Comparison of the seastate during Thane and Nilam cyclones along South East coast of India - using WAM

Abstract: Knowledge on the ensemble wave characteristics such as significant wave height (Hs) during the propagation of a cyclone is important in the planning of mitigation measures along the coastal zone. This is in addition to the design of structures in the nearshore and along the coast for its sustainability. Hence, the wave climate which persist along the south-east coast of India during two different cyclones Thane and Nilam that made landfall in the successive years 2011 and 2012 are simulated using WAM. The model simulation has been validated with field observations. The detailed results are discussed in this paper.