The reflection characteristics and the dynamic pressures exerted on an impermeable wall on the leeward side of permeable wave screens due to action of regular waves were taken up for investigation through theoretical and experimental programs. The two wave attenuating chambers are formed by placing horizontal slotted wave screens consisting of equally spaced circular wave-intercepting elements. The theoretical model is based on the eigenfunction expansion theory for linear waves, which has been successfully applied earlier for evaluating the hydrodynamic performance of vertical slotted screens by Issacson et al. (1998, 1999) and subsequently for pile supported barriers by Laju et al. (2006). The agreement between theoretical and experimental results is found to be good for the tested range of wave conditions. The present theoretical model is also found to be good in predicting the reflection characteristics of multi-chambered breakwaters. The formulation of theory, solution methodology, details of experiments and the results are discussed in this paper. © 2009 Taylor &amp; Francis Group, LLC.

V Sundar

Department of Ocean Engineering

Ranganathan Sundaravadivelu

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Wave attenuation characteristics of chambered breakwater

ISH Journal of Hydraulic Engineering

The reflection and transmission characteristics of double porous barriers (DPB) have been studied through a numerical wave tank investigation. The numerical wave tank is modelled using a finite difference method based numerical scheme, BOUSS-2D. In the present study, the emphasis is given to the wave oscillations between the porous barriers (chamber) and its effect on the hydrodynamic performance. The wave oscillations measured inside the chamber were analysed qualitatively through phase portraits and quantitatively through spectral transformations. The analysis showed interesting features of the wave oscillations for different chamber to wavelength ratio, B/L. A sub-harmonic resonance is observed inside the chamber when B/L»0.2, which leads to reduction in the reflection coefficients, K for the DPB models. In addition, the effects of combination of porosity on the reflection and transmission characteristics of DPB are compared to that of a single porous barrier (SPB) of respective porosity. The comparison of numerical wave tank test results with that derived from a theoretical model based on the eigen-function expansion theory is found to be good. An experimental verification is also carried out to understand the effect of B/L on the wave oscillations inside the chamber. The details of the numerical scheme and analysis of results are presented and discussed in this paper. © 2011 Taylor & Francis Group, LLC.

Characteristics of wave oscillations between two porous barriers

Facilities for handling large draft vessels, modern container ships and tankers have become essential due to the rapid growth in marine traffic. A pile supported skirt breakwater (PSSB) is one of the most promising concepts that could fulfill this requirement as PSSBs are environment friendly and economical for locations where tidal fluctuations are large and soil conditions are poor compared to other types of conventional breakwaters. The structure consists of an impermeable barrier piercing the free surface and extending up to a certain depth of submergence. The barrier which is responsible for attenuating the incident waves through partial reflection is supported on closely spaced concrete or steel piles. The barrier would consist of pre-cast elements that are connected to the piles on site. A numerical model based on the Eigen function expansion theory for linear waves to investigate the reflection and transmission characteristics of a PSSB consisting of single and double rows has been developed. The wave run-up on the skirt of the front row as well as the oscillation of the water surface in between the two rows was also computed. The results on the above stated parameters are reported as a function of wave and structural parameters in a dimensionless form. The numerical results are compared with experimental results and the agreement in general is found to be good. © 2011 Elsevier Ltd.

Applied Ocean Research

Hydrodynamic characteristics of pile supported skirt breakwater models

The response characteristics of a discus data buoy under the action of nonlinear waves are investigated through an experimental set-up in a wave tank. The details of the model, instrumentation, testing conditions and the analysis of the results are presented and discussed in this paper. The nonlinear waves were generated in the wave tank such that their characteristics fall under the Cnoidal and Stokes wave theory regions. The measured wave elevation and responses of the buoy model were analyzed qualitatively through phase-portrait and, quantitatively through spectral and harmonic analysis. In addition, the effects of the nonlinear wave height, wave period and Ursell parameter, U r, on the response characteristics of the buoy model are addressed. Using a linear Transfer Function (TF) obtained from linear waves, an attempt to estimate the nonlinear-wave spectral density from the buoy model dynamics is made and the uncertainties in such predictions are detailed. © 2008 World Scientific Publishing Company and Japan Society of Civil Engineers.

Journal	ISH Journal of Hydraulic Engineering
ISSN	09715010
Open Access	No