Numerical Investigation on Flood Water Sloshing Influence on Intact and Damaged Stability of Ship

Sloshing affects the intact and damage stability of the ship, which causes variation in dynamic metacentric height (GM) under critical load conditions. The transient flooding soon after the ship damage is analyzed, with floodwater accumulation in large space and causing the ship to suffer huge heel angles. The ship motion and stability changes when sloshing becomes high in partially flooded compartments. Most of the previous researches focus on the motion response of ship alone, hence the variation of stability due to sloshing is to be more critically studied. In the present study, three critical damage locations are identified and flooding through these locations are analyzed using the volume of fluids method. The method focus on finding damage ship motion response, flood water dynamics, and coupled dynamics of both. This is studied using the numerical method FLOW3D. Motion and stability behaviour will be different for different damage locations; hence portside, starboard-side, and aft-end bottom damage cases are considered. The effect of compartment shape and damage location on motion response and stability of the damaged ship is highlighted.

Ship control in storm conditions

Приведены выражения для определения периодов собственных поперечных и продольных колебаний судна, как точные, так и приближённые, но в тоже время достаточные для их практического использования на судне. Представлены формулы для расчёта поперечной метацентрической высоты после принятия груза судном перед выходом в море. Выведены формулы для определения критических зон резонансной качки по крену и дифференту, как по скорости судна, так и по курсовому углу по отношению к направлению распространения штормового волнения моря. Представлены формулы для определения кажущегося периода встречи судна с волной, которые являются основой для расчёта резонансных зон. Выведенные соотношения для определения зоны резонанса по скорости судна при заданном курсовом угле и по курсовому углу при заданной скорости судна представлены при условии известного периода штормового волнения моря и курсового угла судна по отношению к направлению распространения волнения моря. Приведены формулы для определения амплитуды качки в условиях резонанса, если отношение периода собственных колебаний судна к кажущемуся периоду волны находится в пределах 0,7 – 1,3. Представлены выражения для определения амплитуд качки по крену и дифференту, вызывающие морскую болезнь у персонала, а также критические значения боковых перегрузок, влияющих на правильность его действия. Expressions for determining the periods of the natural transverse and longitudinal vibrations of the vessel, both exact and approximate, are given, but at the same time sufficient for their practical use on the vessel. The formulas for calculating the transverse metacentric height after the cargo has been accepted by the vessel before going to sea are presented. Formulas are derived for determining the critical zones of resonant pitching in terms of roll and trim, both in terms of the ship's speed and in the heading angle in relation to the direction of propagation of storm waves of the sea. The formulas for determining the apparent period of the ship's meeting with the wave are presented, which are the basis for calculating the resonance zones. The derived relations for determining the resonance zone by the speed of the vessel at a given heading angle and by the heading angle at a given speed of the vessel are presented under the condition of a known period of stormy sea waves and the heading angle of the vessel in relation to the direction of propagation of sea waves. Formulas are given for determining the amplitude of pitching under resonance conditions if the ratio of the period of natural oscillations of the vessel to the apparent period of the wave is within 0.7 - 1.3. Expressions for determining the amplitudes of roll and pitch that cause motion sickness in personnel, as well as the critical values of lateral g-forces that affect the correctness of its action, are presented.

The Effect of Subgrade Coefficient on Static Work of a Pontoon Made as a Monolithic Closed Tank

This article presents the effect of taking into account the subgrade coefficient on static work of a pontoon with an internal partition, made in one stage and treated computationally as a monolithic closed rectangular tank. An exemplary pontoon is a single, ready-made shipping element that can be used as a float for a building. By assembling several floats together, the structure can form a floating platform. Due to the increasingly violent weather phenomena and the necessity to ensure safe habitation for people in countries at risk of inundation or flooding, amphibious construction could provide new solutions. This article presents calculations for a real pontoon made in one stage for the purpose of conducting research. Since it is a closed structure without any joint or contact, it can be concluded that it is impossible for water to get inside. However, in order to exclude the possibility of the pontoon filling with water, its interior was filled with Styrofoam. For static calculations, the variational approach to the finite difference method was used, assuming the condition for the minimum energy of elastic deflection during bending, taking into account the cooperation of the tank walls with the Styrofoam filling treated as a Winkler elastic substrate and assuming that Poisson’s ratio ν = 0. Based on the results, charts were made illustrating the change in bending moments at the characteristic points of the analysed tank depending on acting loads. The calculations included hydrostatic loads on the upper plate and ice floe pressure as well as buoyancy, stability and metacentric height of the pontoon. The aim of the study is to show a finished product—a single-piece pontoon that can be a prefabricated element designed for use as a float for “houses on water”.

Numerical Analysis of the Bottom Thickness of Closed Rectangular Tanks Used as Pontoons

This paper concerns the numerical analysis of closed rectangular tanks made in one stage, used as pontoons. Such structures can be successfully used as floating platforms, although they primarily serve as floats for ‘houses on water’. Amphibious construction has fascinated designers for many years and is becoming, in addition to a great and prestigious location for many purposes, a practical global necessity. Severe weather phenomena that no country is safe from, i.e., heavy rains or floods, combined with the scarcity of space intended for the construction of residential buildings, encourage development at the contact of water and land or on water only. This paper contains an analysis of the static work of tanks with different bottom thickness subjected to hydrostatic load acting on tank walls and the bottom plate and evenly distributed load acting on the upper plate, i.e., major impacts that occur when tanks are used as pontoons. Calculations were made using the finite difference method in terms of energy, assuming the Poisson’s ratio ν = 0. Based on the solutions obtained, charts were made that illustrated the change in bending moments at the characteristic points of the analysed tanks depending on acting loads. The article also includes calculations of buoyancy, stability and the metacentric height for tanks with different bottom thicknesses, with the main purpose being to improve and share knowledge on their safe use as pontoons.

The Influence of the Cuboid Float’s Parameters on the Stability of a Floating Building

Usually, the concept of sufficient stability of a floating structure is connected with the capacity to keep a small heel angle despite the moment of heeling. The variable responsible for these characteristics is the initial metacentric height, which is the relation between the hydrostatic features of the pontoon and the mass properties of the entire object. This article answers the questions of how heavy the floating system should be, what the minimum acceptable draft is, and whether it is beneficial to use internal fixed ballast. To cover various technologies, a theoretical model of a cuboid float with average density representing different construction materials was analysed. The results indicate that the common practice of using heavy and deep floating systems is not always reasonable. In the case of floating buildings, which, unlike ships, can be exploited only under small heel angles, the shape and width of the submerged part of the object may influence the stability more than the weight or draft.

Stability assessment of "Zvezda" Shipbuilding Complex dry dock gate

В процессе проектирования сухого дока, строящегося в г. Большой Камень, у российских специалистов возникли расхождения с проектантами из КНР по вопросам обеспечения остойчивости батопорта и его балластировки. По мнению российской стороны, требование китайских норм к метацентрической высоте (не менее 1,0 м) является чрезмерно завышенным. Кроме того, представлялось желательным использовать постоянный жидкий балласт вместо твёрдого. К решению возникших вопросов были привлечены представители ДВФУ. В работе рассмотрены результаты оценки остойчивости батопорта при использовании твёрдого и жидкого постоянного балласта. Сопоставлены требования к остойчивости батопортов в Китае, Великобритании и Франции. Рассмотрена динамическая остойчивость батопорта, в том числе для случая рывка буксирного троса при отводе батопорта от дока с учётом требований российского регистра. Выполненные исследования были приняты во внимание при окончательном решении вопроса о типе постоянного балласта. The main object of Shipbuilding Complex "Zvezda" shipbuilding complex is a dry dock. The dry dock is located in Bolshoi Kamen city. There are some discrepancies between of Russian and Chinese engineers about the ballast type and stability of dry dock gate. As an example the Chinese stability requirement for metacentric height (at least 1.0 m) is considered as excessively high. In addition two types of dry dock gate ballasts (solid and liquid) were considered. The authors were involved in this research. In this paper we present the results of dry dock gate stability assessment for solid and liquid types of ballast. For this research the dry dock gate stability requirements of China, Great Britain and France standards were compared. The dynamic stability of dry dock gate was considered for the case of a tug rope tension with taking into account the requirements of the Russian register of shipping. The results of this research were taken into account as recommendations for design and construction of the dry dock gate.

Impact of Forced Roll Motion on the Ice Resistance of Modern Icebreaking Bow Geometries

Following the development of low friction hull coatings and azimuthing propulsion for icebreaking vessels, the development of auxiliary systems for reducing ice resistance fell from focus of research. One of these systems is comprised of active heeling tanks which induce a forced roll motion on the icebreaker. Today it is not fully understood how effective or even useful such systems would be for the icebreaking performance in combination with a modern icebreaking hull form. In this study, the impact of active heeling systems on level ice resistance is investigated by performing ice model tests with an icebreaker representing the latest design generation. The level ice thickness used in the model tests corresponds to the maximum continuous icebreaking capability of the evaluated vessel in multi-year ice conditions. Additionally, a calculation method is developed to predict the impact of forced roll motion on the ice resistance. The calculated prediction is evaluated against the model-scale data. Finally, the effectiveness of the active heeling system is evaluated from an engineering perspective: does the active heeling system reduce the power demand, or would the same result be achievable by increasing the propulsion power accordingly. It was found that the roll motion impacts the ice resistance in level ice. The main influence in this regard lies with the tank volume and metacentric height of the icebreaker. Additionally, it was observed that an optimum heel angle dependent on the ice condition can be determined which is not necessarily the highest one achievable. The case study predicts a reduced power demand for a modern icebreaker hull form in harsh ice conditions.

A New Design Criterion to Improve the Intact Stability of Galician Small Fishing Vessels

The first technical factor involved in maritime accidents is related to the lack of intact stability. The current stability criterion, based on fixing a minimum value for each of the different static and dynamic righting arms, is not regarded as satisfactory. Correspondingly, a new criterion based on the transverse metacentric height, dynamic stability up to 70° heel, and critical wave height were considered for fishing vessels less than or equal to 24 m in length. This can be understood as an improvement on the Rahola criterion or an equivalent criterion of dead ship capsize mode, as assumed in the second-generation stability criteria. The proposed criterion, when used in a real case study on the Galician fishing grounds, achieved higher precision. The few vessels that did not comply with the proposed requirement can continue to operate in the area if the Meteorological and Oceanographic Coefficient (CMO) is considered at the time we employ our criteria. As a result, their activity is limited to only a few fishing grounds where adequate weather conditions exist. Finally, the methodology developed can be easily extrapolated to other regions in the world.