Marine Technology - July 2008 - Page#82

<BODY> <span id="lblContents">loading and stability as well as proper training is a key tool to ensure stability safety from the human factor perspective. Peters and Marshall [A33] describe a computer simulator for seamanship training. The simulator is based on FREDYN and capable of quite precisely reproducing ship behavior in waves. The other subject of the paper is active operator guidance ORHEUS (Onboard Risk Performance EvalUation System) with special focus on aircraft operations. Howe and Johansen [A66] describe an education program for fishermen safety expected to reduce the number of fishing vessel capsizes and lives lost. The educational program is designed to ensure that trained people's operational decisions will be based on informed risk considerations nested in fundamental principles of stability. A simple format for Stability Notices for small fishing vessels is introduced by Deakin [A67]. It presents guidance on the transitions between the distinct safety zones defined, in terms of the loading configuration, lifting load, heel angle, or residual freeboard. Guidance on the maximum recommended sea state is given in each case, as well as general advice on maintaining stability. A guidance freeboard mark is recommended as an additional safety guidance. Nilsson and Rutgersson [A69] discusses the design of a damage stability education program for merchant ships. Complementarily, two decision-support systems are discussed as decision aids on a ship bridge in a damage situation. 6.3. Stabilizing systems Roll with large amplitude is a partial stability failure. Even if it does not lead to capsizing, it can be a reason for injury of passengers and crew, loss, damage, or shift of the cargo and, further on, the "trigger" of an accident. That is why roll stabilization devices are not merely means for a comfortable ride, which is important for human performance, but also a safety device; this explains the interest in this subject from the participants of the STAB conference. Kishev and Rakitin [A70] describe design verification for a passive antirolling tank to be installed on 214 m Panamax container carrier. The experiments included testing a model of the tank on three degree of freedom forced oscillation stand and a test of 1:53 scale model with the tank fitted in a model basin in regular and irregular waves. Ribeiro e Silva et al. [A71] presents a methodology of assessment of a roll stabilization system for a 57.5 m semidisplacement naval patrol vessel. The methodology includes consideration of ordinary differential equation of motions with U-type tank, active fins and bilge keels. The paper by Saad et al. [A72] focuses on roll motion of FPSOs, as they may experience a synchronous roll resonance. Theoretical analysis considered nonlinear six degrees of freedom model of ship motion linearized supplemented by the linearized two degrees of freedom dynamical system. A stabilizing device was modeled as a moving mass, with a three and one degree of freedom dynamical subsystem. A model test in deep water basin was used to validate the results from the theoretical study. Grove and Portella [A73] considers ways to decrease roll motions of a 31.9 m small offshore supply boat that may encounter beam seas with a small speed. Bilge keels and antirolling tanks are considered and compared as design alternatives. Liquid motions in stabilizing tanks are investigated by Delorme et al. [A74]. Numerical results obtained by the smoothed particle hydrodynamics (SPH) method are compared with experiments. Results included the first sloshing frequency and ship roll resonant frequency. The SPH method 152 JULY 2008 has also been used in the paper by Skaar et al. [A61] reviewed earlier. 6.4. Stability and naval architecture Maffra et al. [A6] developed an algorithm that uses sequential linear programming to compute the amount of liquid in each tank necessary to reach a given equilibrium configuration for a vessel with minimum displacement of liquids. The automatic loading algorithm also minimizes free surface effects and structural stresses of the vessel. Considering that the upside down construction of medium sized ships is beneficial, a subsequent turnover sequence with the hull floating on the water is described by Bezerra et al. [A7]. The technique allows for application of a small force applied by a crane to accomplish the turnover afloat. The methodology was successfully applied to a 46 m patrol vessel. Based on archaeological findings and evidence from old shipbuilding treatises, Santos et al. [A8] undertook the reconstruction of the ship's lines plan and weight distribution of an early 18th century Portuguese nau. For a number of different loading conditions, the floatability and stability of the vessel were investigated. Stability characteristics were compared with modern stability criteria. 7. Stability of high-speed vessels High-speed vessels find more and more applications for civil and naval purposes. Forces of dynamic lift are created using different physical principles; appearance of these forces may lead to an adverse behavior in waves that is not observed on conventional vessels. Also, change in hull geometry dictated by high speed contributes to the altering of the behavior. Vassalos et al. [A20] describes a comprehensive study of an air-lifted catamaran; this is a new concept combining effects of skirtless air cushion and air lubrication. A mathematical model of the air cushion takes into account air compressibility and considers the free surface problem in the time domain using convolution, while impulse response functions are computed in the frequency domain. Hull hydrodynamic forces are calculated with strip theory. The paper describes calculation of static stability (on hull and on cushion), dynamic stability in waves, stability during maneuver and directional stability. Two papers by Ayaz et al. [A22] and [A23] are focused on the dynamics of high-speed vessels with podded propulsion. A mathematical model combines seakeeping and maneuvering equations and is complemented with terms describing forces created by the pod drives. The model was validated using model test data for pod-driven 220 m RoPax and 275 m container carrier. Numerical analysis also included cases of parametric roll and surf-riding. Another aspect considered is heel during maneuvering caused by podded propulsion. Bertorello et al. [A24] considered several multihull options for a 35 to 40 knots 800 passenger and 250 to 300 car application: catamaran, trimaran (three options round bilge vs hard chine main hull and outriggers, round bilge main hull and outriggers of different length), and a pentamaran. Results of intact and damage stability calculations are compared for these configurations. The paper by Katayama et al. [A25] describes a study of increasing heel angle on a very-high-speed planing craft. Two models were tested in a high-speed model tank; heel angle of 8 deg was observed for one of the models starting from Fn 4.9, another model displayed 20 deg starting from Fn 2.2. Analysis using empirical formulas shows that the reason for MARINE TECHNOLOGY</span> <br /> <br /> <a href="http://www.digitalwavepublishing.com/" title="Digital Magazine">Digital Wave Publishing</a> </BODY>