"uuid","repository link","title","author","contributor","publication year","abstract","subject topic","language","publication type","publisher","isbn","issn","patent","patent status","bibliographic note","access restriction","embargo date","faculty","department","research group","programme","project","coordinates"
"uuid:85cef785-c17c-41d7-9a58-6a183c468523","http://resolver.tudelft.nl/uuid:85cef785-c17c-41d7-9a58-6a183c468523","Hydroelastic analysis of very large floating structures","Andrianov, A.O.I.","Hermans, A.J. (promotor)","2005","Due to the growth of their population, urban development and the corresponding expansion of land use, several countries have decided to build artificial islands in the sea to decrease the pressure on the heavily used land space. The reclamation of the land from the sea is already widely applied, however, there is also an attractive new alternative: construction of very large floating structures (VLFSs). VLFSs can and are already being used for storage facilities, industrial space, wind and solar power plants, bridges, ferry piers, docks, rescue bases, breakwaters, airports, entertainment facilities, military purposes, even habitation, and other purposes. They can be speedily constructed, exploited, and easily relocated, expanded, or removed. The subject of the dissertation is hydroelastic analysis of a very large floating structure, so the motion of a VLFS (modelled by an elastic plate) and its response to surface water waves. Several problems of the interaction between the VLFS and water waves are treated in the dissertation. The plate deflection, free-surface elevation, reflection and transmission of water waves are studied using different theories of applied mathematics, mechanics and hydrodynamics. New method for the hydroelastic analysis of the VLFSs, an integro-differential equation method, is proposed, justified, and applied in the dissertation. Also, the geometrical-optics approach, the ray method, and the Lindstedt method are used.\par An analytical solution and numerical results are derived for various shapes and dimensions of the floating plate and three different models of water depth. The problem background and introduction, literature survey and information on VLFSs are given in chapter 1. Chapter 2 describes the general theory, the basic equations and conditions, introduces and formulates particular problems considered, and proposes a method of solution. The problems for the following models and horizontal shapes of a very large floating platform are solved in chapters 3--7: a semi-infinite plate and a strip of infinite length, a circular plate, a ring-shaped plate, a quarter-infinite plate, and a plate of finite, but small, thickness. Analytical solutions together with representations and operations are described for specific cases. Numerical results are obtained for practically important and relevant situations.\par General conclusions, recommendations and a discussion on VLFSs in and of the future are given in chapter 8.","diffraction; dispersion relation; elastic plate; fluid-structure interaction; freesurface elevation; hydroelastic analysis; hydroelastic response; incident surface waves; initiated wave pattern; integro-differential equation; offshore structure; plate deflection; plate-water interaction; reflection; transmission; very large floating platform (VLFP); very large floating structure (VLFS); water depth","en","doctoral thesis","","","","","","","","","Electrical Engineering, Mathematics and Computer Science","","","","",""
"uuid:938839aa-01ab-4c64-bf6e-448ed519945e","http://resolver.tudelft.nl/uuid:938839aa-01ab-4c64-bf6e-448ed519945e","Aircushion Supported Mega-Floaters","Van Kessel, J.L.F.","Huijsmans, R.H.M. (promotor)","2010","The increase of the global population and expanding coastal mega-cities will necessitate an innovative pursuit of the utilization of the ocean space in which mega-floaters will play an important role in the future. These types of structures are very large floating artificial islands that can be used for various facilities and purposes similar to those on land. Compared to landfill methods mega-floaters generally have a smaller environmental impact than traditional land reclamation projects. They are indifferent to earthquakes and can be constructed at relatively low cost in a short period of time, independent of ocean depth and seabed conditions. Furthermore, the existing facilities can be easily expanded while they are functional and the space available inside the structure offers prospects for various activities and different use. This thesis describes a method to predict the dynamic behavior of aircushion supported mega-floaters in waves. These types of structures are supported by a large volume of air which is entrapped underneath the structure by vertical walls that extend sufficiently far underneath the water surface in a way that no air will escape when waves pass by. The method is based on a linear three-dimensional potential theory using modal expansions and a linear adiabatic law to describe the air pressure within the aircushion. It is the first method that is able to accurately predict the three-dimensional dynamic behavior and stresses of flexible aircushion supported structures of arbitrary shape in waves. The structure around the aircushion is modeled in the usual way by means of panels representing pulsating sources which are distributed over the mean wetted surface of the body. The free water surface underneath the structure is modeled by panels laying in the mean free surface of each aircushion. All panels associated with an aircushion represent a body without material mass, but having added mass, damping, hydrostatic restoring and aerostatic restoring characteristics. The results of this study indicate that the behavior of aircushion supported structures can be well predicted by means of a three-dimensional linear potential method. In case of rigid bodies, the numerical results were validated with model tests. Model tests with a conventional flexible barge served to validate the hydroelastic method. Unfortunately no experimental results are available for flexible aircushion supported structures. Therefore the numerical results of these structures are verified with analytical and FEM computations. Both the model tests and computations have shown that the application of aircushions can significantly influence the behavior of floating structures. The effect on the structural loads is significant and is particularly pronounced in the wave induced bending moments which are considerably reduced by the aircushions. A conventional mega-float structure has to be protected by breakwaters if it is located in open seas. These breakwaters will reduce the wave loads on the structure, but add to the total costs of the mega-float project. Another option is to support the structure by aircushions to reduce the wave induced bending moments and consequently the stresses. In general, the results of this study have shown that an aircushion supported structure will have significant advantages compared to conventional mega-floaters. In addition, the computational method as developed and proposed proved to be a suitable tool to optimize the cushion configuration for a particular application.","mega-float,; very large floating structure (VLFS); aircushion support; compressibility; fluid-structure interaction; hydroelastic analysis; motions; dynamic behavior; wave forces; drift forces; wave field; shear forces; bending moments; stresses; frequency domain; floating runway","en","doctoral thesis","","","","","","","","2010-02-01","Mechanical, Maritime and Materials Engineering","Offshore Engineering & Ship Hydromechanics","","","",""