Topic
Metacentric height
About: Metacentric height is a research topic. Over the lifetime, 219 publications have been published within this topic receiving 1505 citations.
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01 Jan 2015
TL;DR: In this paper, the authors investigated three control laws to suppress the induced pitch motion by adding pitch rate, pitch angle or pitch acceleration into the feedback control loop, and extensive numerical simulations were conducted with a semi-submersible platform for each control law.
Abstract: For general dynamic positioning systems, controllers are mainly based on the feedback of motions only in the horizontal plane. However, for marine structures with a small water plane area and low metacentric height, undesirable surge and pitch oscillations may be induced by the thruster actions. In this paper, three control laws are investigated to suppress the induced pitch motion by adding pitch rate, pitch angle or pitch acceleration into the feedback control loop. Extensive numerical simulations are conducted with a semi-submersible platform for each control law. The influences of additional terms on surge—pitch coupled motions are analyzed in both frequency and time domain. The mechanical constraints of the thrust allocation and the frequency characters of external forces are simultaneously considered. It is concluded that adding pitch angle or pitch acceleration into the feedback loop changes the natural frequency in pitch, and its performance is highly dependent on the frequency distribution of external forces, while adding pitch rate into the feedback loop is always effective in mitigating surge—pitch coupled motions.
Dissertation•
01 Jan 2012
TL;DR: In this paper, the authors proposed an alternative solution to this conventional transportation proposed by the utilization of a logistical HUB, which is based ferries doing the transportation of personnel from shore to the HUB and helicopters doing the remaining, relatively short, transfer from the hulks to the respective platforms.
Abstract: The conventional way of transporting personnel from shore to offshore platforms is done by helicopter. For large distances of transportation this results in high costs due to the limitations in the maximum number of persons each helicopter can transport per trip and due to the high prices on helicopter fuel. In this thesis is an alternative solution to this conventional transportation proposed by the utilization of a logistical HUB. The concept is based ferries doing the transportation of personnel from shore to the HUB and helicopters doing the remaining, relatively short, transfer from the HUB to the respective platforms. The HUB evaluated is based on the characteristic Sevan 650 design, having a cylindrical shape with diameter D=78m in the waterline. The models that have been analyzed in this thesis were modeled in GeniE, the hydrodynamic analyses were done in Wadam and the post processing was performed using Postresp. Models of a platform with a single tunnel cut out with varying tunnel length L have been evaluated, and the motions of these models as well as the surface elevation inside the tunnel were studied in detail. It was recorded a two peaked response in heave for the models with tunnel lengths ranging from 30m
01 Jan 2022
TL;DR: An integrated procedure for use at the preliminary design stage of such structures that systematically facilitates their overall design is proposed that introduces a unique approach called the “required GM” method.
Abstract: Herein, the authors describe an overall approach to the architectural design of floating structures such as floating houses. The primary aim of this study is not to present a method for stabilizing floating structures, but rather to provide a design synthesis method for use when designing such structures. More specifically, we propose an integrated procedure for use at the preliminary design stage of such structures that systematically facilitates their overall design. As an inclining platform could endanger the people on board, it is necessary to determine an adequate metacentric height in order to prevent such occurrences. This measurement, which is defined as the distance between the center of gravity of a floating structure and its metacenter, quantifies the initial static stability of a floating body. Based on this idea, we consider the associated problems as well as the methods used in practical procedures, and combine them to introduce a unique approach called the “required GM” method. We also discuss the different and various aspects used in basic configuration determinations of floating architectural structures, such as the aspect of static stability and the overall process used at the conceptual design stage. In addition, illustrative examples of an idealized floating platform embodying the simplest possible structures are provided to illustrate these points.