Prediction of shoreline behaviour for Madras, India-a numerical approach

A satellite port has been proposed about 14.8 km north of Madras port on the east coast of India. As the interference of a satellite port with the existing pattern of longshore sediment transport will generate coastal imbalance in the region, a numerical model study involving sediment transport and combined wave refraction-diffraction was conducted to predict the shoreline behaviour. A realistic approach to the study was made to meet the objectives by considering wave height-wave period distributions in the region and duration and sequence of their occurrence during major monsoon seasons. This method of analysis enabled us to predict: (i) the extent of general shoreline advancement, particularly in front of a tidal inlet—a source of the cooling water requirement for an existing thermal power plant; (ii) the extent of the coastal region that will be affected owing to recession of shoreline and its impact on: (a) the fishing community living along the coastal stretch; (b) the national highway running along the coast; and (c) the changes in nearshore bathymetry. Based on the studies, management plans were drawn to safeguard the coastal region from imbalances that will arise out of construction of the satellite port. This paper highlights the effects of a satellite port on the coastal region and the need for proper management.     

The microstructure of lime-stabilized marine clay

The treatment of fine-grained soils with lime makes the soil system less sensitive to the changes in stress and other environmental factors. In the present investigation an attempt has been made to examine the nature of reaction products formed in a marine clay due to lime treatment using scanning electron microscopy (SEM) studies. The lime-induced microstructural changes in a marine clay have been investigated using SEM. The test results indicate that there is an overall improvement in the structure of the soil system resulting in a porous system due to the formation of new reaction products.     

Formation and distribution of manganese nodule deposit in the northwestern margin of Clarion-Clipperton fracture zones,northeast equatorial Pacific

In the northwestern margin of the Clarion and Clipperton fracture zones, manganese nodules are latitudinally variable in character, resulting from the progressive (re)generation of nodules since the Oligocene as the Pacific Plate migrates northwestward beneath the equatorial production zone. Complemented by the surface water productivity, bottom current activities have concentrated nodules in the Oligocene to Miocene siliceous clay. Resedimentation processes on nodules form three types of nodules with concentric structures and 10 Å-manganaterich bottoms, by periodically causing the diagenetic growth of nodules within the topmost sediment layer.     

Numerical modelling of tsunami propagation in the open Black Sea

This paper focuses on the numerical modelling of tsunami propagation in the open Black Sea. Two types of numerical models are discussed: a model for the radial propagation of long waves and an evolutionary finite-difference prognostic model. Experimentally derived numerical data on the model source of tsunamis are reported. Translated by Vladimir A. Puchkin.     

A formal derivation and numerical modelling of the improved Boussinesq equations for varying depth

A formal derivation of the improved Boussinesq equations of Madsen and Sørens (1992) is presented to provide the correct forms of the depth-gradient related terms. Linear shoaling characteristics of the new equations are investigated by the method of Madsen and Sørensen (1992) and by the energy flux concept separately and found to agree perfectly, whereas these approaches give conflicting results for the equations derived by Madsen and Sørensen (1992). Furthermore, Nwogu's (1993) modified Boussinesq model is found to produce a linear shoaling-gradient identical with the present work. Numerical modelling of the derived equations for directional waves is carried out by three-time-level finite-difference approximations. A higher-order radiation condition is implemented for effective absorption of the outgoing waves. Several test cases are included to demonstrate the performance of the model.     

Drag force on a circular cylinder in unseparated laminar high Reynolds number nonlinear random oscillatory flow

The stochastic properties of the drag force maxima on a circular cylinder subjected to nonlinear random waves are investigated. Unseparated laminar high Reynolds number flow is considered. A simplified approach based on second order Stokes waves is presented, including the sum-frequency effect only. It is demonstrated how a drag force formula valid for regular linear waves can be used to find the cumulative distribution function of individual drag force maxima for nonlinear irregular waves. Here the [Wang, 1968] drag force coefficient is used.