A simple low cost wave measurement system
G. Vijayakumar, K. Pandurangan and D. Govindarajulu
Department of Civil Engineering, Pondicherry Engineering College, Pondicherry – 605014

Accurate measurement or prediction of wave climate data is required for Coastal Zone development activities. This needs instrumentation at affordable costs. The objective of the study is to develop an instrument that is inherently low cost, low power consumption, smalland yet is capable of excellent performance, both static and dynamic. The authors have developed a physically small but highly accurate wave measuring instrument, which converts wave data from the displacement frame into digital mode using a Rotary type potentiometer and ADC unit. The embedded processor in the module performs the wave height computations. The unit has both high initial accuracy and longterm stability. The wave characteristics obtained from the developed instrument (Wave float gauge) compare very well with the result from the measurement using pressure transducer. Rigorous long term testing of the stability of the instrument has been checked for a period of two year.

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Design of a low frequency class VII Flextensional Transducer
K.P.B. Moosad, Pushpa Abraham and R.M.R Vishnubhatla
Transducer Group, Naval Physical and Oceanographic Laboratory, Kochi 682 021.

Design of a compact Class VII Flextensional Transducer, resonating at 2.5 kHz is described. Modeling using the Finite Element Analysis (FEA) package ATILA is made use of as a design tool, in order to optimize some of the parameters. Experimental results obtained using a prototype fabricated in H30 aluminium alloy are also presented.

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Potential of drowned river valley estuaries on Indian West coast for development and harnessing
U.V. Purandare and Prabhat Chandra
Central Water and Power Research Station, Khadakwasla, Pune - 411 024

Many of the ‘ Drowned River Valley Type of Estuaries' on the west coast of India are endowed with large potential for development of ports, fisheries harbours etc. due to the natural protection, stable and deep natural depths thereby involving minimum expenditure on the capital cost of breakwaters, dredging etc. Since these estuaries also receive large magnitudes of fresh water discharges during monsoon season most of which get drained inthe Arabian Sea presently, suitable storages of fresh water may be created throughout the year within the tidal reaches by constructing low crested gated weirs. The typical drowned river valley estuaries in Maharashtra and Goa states on the west coast of India, i.e., Rajapuri estuary, Jaigad on the Shastri estuary and Mandovi-Zuari estuarine system offer very good sites for such potential developments.

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Thermal studies & experimental investigations on a 0.25 m 2 Solar Gel Pond
N. Sozhan, T.Kaliyappan, S. Rajagopan and E. Vijayakrishna Rapaka
Mechanical Engineering Department, Pondicherry Engineering College, Pondicherry-605 014

The Solar Gel Pond is an innovative concept, which overcomes many of the shortcomings of the conventional salt gradient solar pond. The non-convective salt gradient layer is replaced by a transparent polymer gel layer, which floats on a NaCl solution used in the storage zone. The polymer gel (Carbowax) used was found to be insoluble in different concentrations of NaCl solution, good transmissivity characteristics, low cost and was found to be stable.

An attempt has been made to analyze the performance of the solar gel pond of 0.25 m 2 area located at Pondicherry, India (Latitude 11.56 o N, Longitude 79.53 o E). Experimental investigation has been carried out during the months of April & May 2004. The maximum storage temperature was found to be 60 o C and temperature difference between the storage layer and gel layer was found to be around 10 o C. A theoretical study was carried out using Bansal and Kaushik modified model for the Solar Gel Pond. The outcome of the theoretical study has been validated using the experimental results.

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Bottom mounted seabed mooring frame for high current field
K. Ashok Kumar¹, P. Chandramohan², P. S. Pednekar¹ , S. G. Diwan¹
¹National Institute of Oceanography, Dona Paula, Goa,
²Indomer costal Hydraulics (P) Limited, Chennai

Longterm current measurements for a period of 14 months were taken up by National Institute of oceanography at high current regime in Gulf of Khambhat. The measurement was intended at seabed for obtaining vector averaged current speed and direction on the sea surface and at a fixed five layers. The company supplied frame was not suitable to use at the proposed measurement location, owing to random oscillation in the seabed, strong currents and high concentration of sediments in the water column. The authors have designed a special frame to withstand for above problems and the measurements were carried out successfully for such harsh environment, first time in India. The details of the design and the measurement techniques are described in the paper.

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