Loads for use in the design of ships and offshore structures

Sulphate attack and ettringite formation in the lime and cement stabilized marine clays

Efficiency investigation on energy harvesting from airflows in HVAC system based on galloping of isosceles triangle sectioned bluff bodies

In August 2005, a team surveyed the effects of the December 2004 Indian Ocean tsunami on the southern coast of Oman. Runup and inundation were obtained at 41 sites, extending over a total of 750 km of shoreline. Measured runup ranged from 3.25 m in the vicinity of Salalah to a negligible value at one location on Masirah Island. In general, the largest values were found in the western part of the surveyed area. Significant incidents were documented in the port of Salalah, where a 285-m-long vessel broke its moorings and drifted inside and outside the port, and another ship struck the breakwater while attempting to enter the harbor. The general hazard to Oman from tsunamis may be greatest from the neighboring Makran subduction zone in western Pakistan.

Sri Lanka Field Survey after the December 2004 Indian Ocean Tsunami

The purpose of offshore seawater intake is to provide a continuous supply of seawater with proper quantity and quality. The large volume and specified water quality requirements, offshore intake wells are preferred. The adequate and economical supply of seawater from the offshore intake well depends on the performance of the pumping system. In a typical intake well, the pumping equipment is placed below the water surface based on the free surface water oscillation inside the well. The loads exerted by the incoming waves and the free surface water oscillation will affect the pumping performance. This phenomenon should be reduced for smooth and efficient pumping operation. To achieve this, some auxiliary equipment like curtain wall is introduced into the intake well. This type of internal structure can regulate the flow and dissipate the incident wave energy up to some extent. Moreover, they can obstruct the formation of vortices and eddying. The present study focuses on the internal hydrodynamics of an offshore intake well with a porous curtain wall. A 1:20 scale model is tested with regular waves in the shallow wave basin and wave run-up, rundown, free surface water oscillation inside the well and the pressure acting on the curtain wall is measured. Then, the influence of the porosity on the free surface water oscillation is investigated by changing the porosity.

Effect of Porous Curtain Wall on the Internal Hydrodynamics of an Offshore Intake Well

A numerical investigation has been carried out to obtain a non-dimensional grid size (grid size/ tsunami base width) for the near shore discretisation of computational domains for long wave modelling. A 1D domain has been considered in which, the flow has been solved by 1D shallow water equations with vertically integrated flow variables. The sensitivity study of the grid size was carried out in the 1D channel with an open boundary at one end and shelf boundary at the other end. The grid size was varied from 10 m to 1000 m and its effect on the computation of the tsunami run-up along the shoreline has been investigated. The non-dimensional grid size for the computation of run-up was optimised by comparing the non-dimensional run-up (tsunami run-up/initial tsunami height) and a threshold value of 5.0e-4 was obtained. Further, the study was extended to real scenario by adopting various grids for the shelf region of northern Tamil Nadu coast, south east coast of India in 2D and a suitable grid size was obtained.

Identification of Suitable Grid Size for Accurate Computation of Run-up Height

The effect of drift angle on a ship is investigated through towing tank tests and using Computational Fluid Dynamics (CFD). Resistance and wave elevations obtained from the computational study are validated with experimental results. Detailed free surface, mean velocity and pressure flow fields on the hull surface are obtained from the computational study for Fn ranging from 0.16 to 0.22 and for drift angle β = 0, 5 and 10°. The lateral force, yaw moment and asymmetric flow characteristics are brought out in the computational study.Copyright © 2006 by ASME

On the Prediction of Hydrodynamic Forces Acting on a Ship Moving at Constant Drift

The dynamic pressures exerted on a vertical wall due to cnoidal waves have been investigated in presence and absence of model vegetation on its seaside. The pressures were measured at 3 different elevations along the wall. Tests were conducted with waves of constant height of 0.11m, with its period was varying between 5 and 20secs, thus covering a wide range of Ursell parameter varying between 18 and 700. The model vegetation was positioned adjacent to the wall on its seaside. All the vegetal characteristics including their rigidity are carefully modelled. The peak pressures (pmax) were extracted from the measured time series and are presented in a dimensionless form as a function of parameters governing the characteristics of waves and plantation. Two types of configurations of the green belt with the individual stems of vegetation fixed in tandem and staggered arrangement were considered for the tests. The study indicates that the staggered arrangement of plantation is more effective in attenuating the ...

https://journals.sagepub.com/doi/pdf/10.1260/1759-3131.2.3.169

Role of Vegetal Configuration on the Pressures Due to Cnoidal Waves on a Wall

Fluid structure Interaction (FSI) is important in analysis of: (1) Cardio-vascular dynamics; (2) Underwater/ Offshore structures; (3) Aircraft wings and turbine blade designs; (4) Design of tall structures/buildings; (5) high speed hard disk drives etc. At present, such capabilities are being incorporated, if any, only to a limited extent in commercial CFD codes leaving the engineers to develop their own codes. In the current study, a hydro-elastic problem of an underwater structure has been considered. Traditionally, the hydrodynamics and the structural dynamics are solved using finite difference/boundary element methods and finite element method (FEM) respectively. Moreover, the governing equation for fluid and structure are usually written in Eulerian and Lagrangian reference frames - posing further difficulties for coupling the two systems. In this research, both the fluid and structural systems are solved by the finite element method using a mixed Eulerian-Lagrangian scheme, where, fluid mesh moves and adapts to new free surface and structural positions. A full non-linear free surface implementation is considered. A mesh adaptation using Laplacian smoothing is performed to reduce the need for re-meshing the domain frequently. The scheme is validated with solutions available in the literature and extended to the present FSI problem with non-linear free surface boundary condition.

K. Murali

Papers

Effect of Porous Curtain Wall on the Internal Hydrodynamics of an Offshore Intake Well

Identification of Suitable Grid Size for Accurate Computation of Run-up Height

On the Prediction of Hydrodynamic Forces Acting on a Ship Moving at Constant Drift

Role of Vegetal Configuration on the Pressures Due to Cnoidal Waves on a Wall

Finite element analysis of non linear fluid structure interaction in hydrodynamics using mixed lagrangian-eulerian method