Динамика опрокидывания водоизмещающего судна при затоплении и действии наклоняющего момента

Рассматриваются вопросы плавучести и остойчивости речного водоизмещающего судна в процессе его затопления при сложном внешнем воздействии. Строится математическая модель динамики опрокидывания судна в нелинейной постановке с учетом изменения нагрузки. Охарактеризована совокупность внешних сил и методы их представления. Алгоритм решения системы дифференциальных уравнений построенной модели, включая модули определения гидростатических и массово-центровочных характеристик корпуса, представлен укрупнённой блок-схемой. Приведены результаты тестовых расчетов гидростатических характеристик, полученных с помощью программной реализации разработанного алгоритма на примере корпуса пассажирского судна массового проекта 26-37 типа Октябрьская революция и исследован процесс его опрокидывания в результате затопления на фоне воздействия кренящего и дифферентующего моментов. Показано, что предлагаемая методика позволяет учесть большее число расчетных ситуаций, в которых следует выполнять анализ остойчивости судов. Исследования имеют практическую значимость и направлены на разработку модели системы поддержки принятия капитаном решений о готовности к использованию штатных технических средств спасения пассажиров и экипажа при угрозе скоротечного затопления судна.The article discusses the issues of floatage and stability in the process of flooding of a displacement vessel with a complex external impact. A mathematical model of the dynamics of the hull in a nonlinear setting when the load changes is proposed. A set of external forces and methods for their presentation are determined. The algorithm for solving the system of differential equations of the model, including modules for determining the hydrostatic and mass-centering characteristics of the body, is represented by an enlarged block diagram. Using the software implementation of the algorithm, test calculations of the hydrostatic characteristics of the hull were carried out, the process of the ship capsizing as a result of flooding against the background of heeling and trimming moments was studied. It is shown that this method allows to take into account a greater number of design situations in which an analysis of the stability of ships should be performed. The studies have practical importance in the development of a system for supporting the adoption by a captain of a river displacement vessel of decisions on readiness to use standard technical means to save passengers and crew in the event of a threat of fleet flooding.

Study on the Safety Degree of Ship Capsizing in Stochastic Waves

To quantify ship capsizing, from the energy perspective, the safety degree of a ship in waves is estimated based on stochastic Melnikov function and phase space transport theory. Considering the influence of nonlinear damping moment, nonlinear restoring moment, as well as the random waves, a nonlinear single degree of freedom differential equation for ship rolling is established. Transform the random wave moment from time domain to frequency domain by fast Fourier transformation, the random Melnikov function and rate of phase flux are extended to include the effects of navigation speed and heading angle and the safety degree of ship capsizing is quantified according to its statistical characteristics. Through an example, the accuracy of Melnikov function and phase space transport theory are verified and the effects of ship speed and heading angle on phase space transport rate are also quantified. This method is demonstrated properly to quantify the safety degree of ship capsizing and some valuable reference can be provided for the further research on ship stability criteria.

Numerical Method Research on Nonlinear Roll System of Large Container Ship

When dealing with the ship-roll problem, the roll motion is mainly regarded as a single degree-of-freedom dynamical system, and the nonlinear properties are reflected in the nonlinear damping term and restoring moment term. Previous studies have shown that transverse chaotic phenomenon means the damage of ship-roll stability which will lead to ship capsizing, and for ultra large container ships, the wind area above water surface can not be neglected, which turns the ship-roll system into asymmetric dynamical system. The concept of safe basin is usually used to express the boundedness of motion. It is defined as the set of bounded solution to dynamical system, and the erosion phenomenon of safe basin is normally explained as the global instability. This concept was firstly brought out by Thompson [1] when he studied the problem of ship capsizing and then was applied to different fields of engineering. Based on this background, the following three tasks are completed in this paper. a) For the calculation of chaos threshold, two numerical methods, namely, Pade approximation and Gauss-Legendre integration are adopted, analyzed and compared. b) One 9200TEU container ship is selected and the chaos threshold is calculated by virtue of Gauss-Legendre method. As numerical verification, the gradually erosion phenomenon of ship’s safe basin is observed and phase trajectories of points located in broken domain are traced; c) When encountered with crosswind (When winds are not parallel to or directly against the line of travel, the wind is said to have a crosswind component; that is, the force can be separated into two vector components, a crosswind component and a headwind or tailwind component.), the symmetry of ship-roll system begin to break. In the last part of this paper, the effect of crosswind on safe basin, asymmetry, and stability are studied.