scholarly journals Ship control in storm conditions

2021 ◽  
pp. 200-206
Author(s):  
Д.А. Скороходов ◽  
Ю.Е. Крылов ◽  
А.Л. Стариченков
Keyword(s):  
Sea Waves ◽  
Longitudinal Vibrations ◽  
Natural Oscillations ◽  
Derived Relations ◽  
Storm Waves ◽  
Ship Control ◽  
Heading Angle ◽  
Critical Zones ◽  
Metacentric Height ◽  
Natural Transverse

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.

scholarly journals On Experiment of Determining the Relationship between Ship Maneuverability and Gravity of Metacenter using Ship Model

2019 ◽  
Vol 8 (11) ◽  
pp. 2060-2064
Keyword(s):  
Science And Technology ◽  
Quantitative Relationship ◽  
Control Problems ◽  
Ship Maneuvering ◽  
Scaled Model ◽  
Ship Model ◽  
Ship Maneuverability ◽  
Ship Control ◽  
Metacentric Height ◽  
The Relationship

Understanding of ship maneuverability and factors effecting to ship maneuverability is important to naval architectures and marine navigators. In ship control problems, the ship maneuvering characteristic must be considered before designing the controllers. With the development of science and technology, it allowed the studies of ship maneuvering to be performed in computation simulations. However, there are always the different results between computation simulation and the fact. For that purpose, this article presents an experiment to establish the quantitative relationship between metacentric height and ship maneuverability using scaled model ship

scholarly journals Boulder accumulations related to extreme wave events on the eastern coast of Malta

2015 ◽  
Vol 3 (10) ◽  
pp. 5977-6019 ◽  
Author(s):  
S. Biolchi ◽  
S. Furlani ◽  
F. Antonioli ◽  
N. Baldassini ◽  
J. Causon Deguara ◽  
...  
Keyword(s):  
Eastern Coast ◽  
Hydrodynamic Equations ◽  
Storm Events ◽  
Sea Waves ◽  
Extreme Waves ◽  
Extreme Wave ◽  
Storm Waves ◽  
Hellenic Arc ◽  
Intense Storm ◽  
Wave Heights

Abstract. The accumulation of large boulders related to waves generated either by tsunamis or extreme storm events has been observed in different areas of the Mediterranean Sea. Along the NE and E low-lying rocky coasts of Malta tens of large boulder deposits have been surveyed, measured and mapped. These boulders have been detached and moved from the seafloor and lowest parts of the coast by the action of sea waves. In the Sicily–Malta channel, heavy storms are common and originate from the NE and NW winds. Conversely, few severe earthquakes and tsunamis are recorded in historical documents to have hit the Maltese archipelago, originated by seismicity activity related mainly to the Malta Escarpment, the Sicily Channel Rift Zone and the Hellenic Arc. We present a multi-disciplinary study, which aims to define the characteristics of the boulder accumulations along the eastern coast of Malta, in order to assess the coastal geo-hazard implications triggered by the sheer ability of extreme waves to detach and move large rocky blocks inland. The wave heights required to transport coastal boulders were calculated using various hydrodynamic equations. Particular attention was devoted to the quantification of the input parameters required in the workings of these equations. The axis sizes of blocks were measured with 3-D digital photogrammetric techniques and their densities were obtained throughout the use of a N-type Schmidt Hammer. Moreover, AMS ages were obtained from selected marine organisms encrusted on some of the boulders in various coastal sites. The combination of the results obtained by hydrodynamic equations and the radiocarbon dating suggests that the majority of the boulders has been detached and moved by intense storm waves. Nonetheless, it is possible that some of them may have been transported by tsunami.

scholarly journals О подходах к созданию системы автоматизированного мониторинга остойчивости судна

2020 ◽  
Author(s):  
A.N. Suslov ◽  
O.V. Odegova ◽  
S. Tanshi
Keyword(s):  
Real Time ◽  
Dynamic Stability ◽  
Monitoring System ◽  
Current Situation ◽  
Automation System ◽  
Stability Conditions ◽  
Sea Waves ◽  
Fishing Vessels ◽  
Intact Stability ◽  
Metacentric Height

В работе предлагаются подходы к созданию системы автоматизированного мониторинга остойчивости судна, что является актуальным в связи с существующей вероятностью опрокидывания неаварийного судна на волнении при эксплуатации рыболовных судов, судов вспомогательного флота, а также судов, осуществляющих различные грузоподъемные операции. Существующие подходы по оценке остойчивости неповрежденного судна ориентированы на использование ряда приближенных зависимостей. В результате величины метацентрических высот оказываются намного выше действительных, особенно на слабом волнении. По мнению авторов в основе системы оперативной оценки остойчивости судна должны выступать величины, на которые можно реально опереться при анализе текущего состояния судна, а именно параметры остойчивости судна, измеряемые в режиме реального времени непосредственно в процессе навигации. На основании данных, получаемых от предлагаемой авторами системы, в режиме неаварийной эксплуатации судоводитель, получив предупреждение, может изменить параметры движения судна (или подъема груза) на безопасные. В случае аварийной ситуации (затопление отсеков) оповещение от системы позволят предупредить судоводителя о необходимости пассажирам и экипажу срочно покинуть аварийное судно. Предлагаемые в данной статье подходы определяют новые направления научных исследований в теории корабля, проектировании и эксплуатации судов.The article describes new approaches for stability automation monitoring system creation. This theme is actual in a view of the capsize probability for several types of vessels during the exploitation in a real sea waves condition. Such condition is very habitual for fishing vessels as well as for auxiliary fleet vessels and also it can take place during the vessel balanced hoisting. Now all methods to solve the question of dynamic stability are based on approximate calculations which gives the metacentric height value higher than it might be in real. Article authors are of opinion, that it is necessary to use the real current figures which will be the foundation of current vessel condition calculations made during the exploitation in a real time. Based on information which could be received from the vessels automation system described by authors, the crew could get a warning if intact stability conditions are close to limits. It gives a possibility to change parameters of the current situation of the vessel to avoid any risk of the capsizing. Authors approaches define the new direction for research investigation in a theory of the vessel design and safety exploitation.

scholarly journals Specifics of determining the tension forces of the cable-stayed bridge elements

2018 ◽  
Vol 239 ◽  
pp. 05011
Author(s):  
Ivan Chaplin ◽  
Andrey Yashnov
Keyword(s):  
Experimental Methods ◽  
Practical Significance ◽  
Natural Oscillations ◽  
Specialized Software ◽  
Cable Stayed Bridge ◽  
Bridge Structures ◽  
Cable Stays ◽  
Design Stress ◽  
Natural Transverse

Objective: to improve the method of determining the force in the cable stays by frequencies of natural transverse oscillations. Methods: synthesis and analysis of theoretical and experimental data, experimental methods for studying the structures. Results: in the paper, the problems of determining the tension forces of the cable stays by the frequencies of their natural oscillations are considered taking into account various factors (the design of anchor fastenings, the angle of inclination and sagging of the cable stay, the change of temperature). The estimation of possible errors in calculations is given. The degree of coincidence of the actual and design stress-strain state of the cable stays depends on the correctness of accounting the influence of the factors considered. The effect of the temperature change and the anchor fastening structure on the frequency of the natural oscillations of the cable stays has been experimentally tested. The recommendations on the determination of the forces in the cable stays by dynamic parameters are given. A method for controlling the tension forces of the cable stays and specialized software “Vant” (“Cable”) for automation of the measurement process are developed. The method has been tested on several bridge structures that have cable-stayed elements. Practical significance: the ability to use the developed method for controlling the tension forces of cable-stayed elements during the operation of artificial structures.

ANALYSIS OF SUPPRESSION OF LONGITUDINAL VIBRATIONS IN RODS WITH MATERIAL PERIODICITY

2019 ◽  
Author(s):  
Jean Paulo Carneiro Junior ◽  
Rodrigo Borges Santos ◽  
Douglas Bueno
Keyword(s):  
Longitudinal Vibrations

DETERMINATION OF THE FUNCTION OF THE ROD’S CROSS-SECTIONAL AREA USING VIBRATION EIGENFREQUENCIES

2020 ◽  
Vol 0 (4) ◽  
pp. 19-24
Author(s):  
I.M. UTYASHEV ◽  
◽  
A.A. AITBAEVA ◽  
A.A. YULMUKHAMETOV ◽  
◽  
...  
Keyword(s):  
Cross Sectional Area ◽  
Variable Cross ◽  
Sectional Area ◽  
Longitudinal Vibrations ◽  
Cross Sectional ◽  
Method Error ◽  
Various Boundary Conditions ◽  
Elastic Fixation ◽  
Crosssectional Area

The paper presents solutions to the direct and inverse problems on longitudinal vibrations of a rod with a variable cross-sectional area. The law of variation of the cross-sectional area is modeled as an exponential function of a polynomial of degree n . The method for reconstructing this function is based on representing the fundamental system of solutions of the direct problem in the form of a Maclaurin series in the variables x and λ. Examples of solutions for various section functions and various boundary conditions are given. It is shown that to recover n unknown coefficients of a polynomial, n eigenvalues are required, and the solution is dual. An unambiguous solution was obtained only for the case of elastic fixation at one of the rod’s ends. The numerical estimation of the method error was made using input data noise. It is shown that the error in finding the variable crosssectional area is less than 1% with the error in the eigenvalues of longitudinal vibrations not exceeding 0.0001.

Wind speed data analysis for predictions of sea waves in Bitung Coastal Waters

2013 ◽  
pp. 35 ◽  
Author(s):  
Joanes E Koagouw ◽  
Gybert E Mamuaya ◽  
Adrie A Tarumingkeng ◽  
P A Angmalisang
Keyword(s):  
Data Analysis ◽  
Wind Speed ◽  
Coastal Waters ◽  
Transition Period ◽  
Marine Resources ◽  
Land Uses ◽  
Sea Waves ◽  
North West ◽  
North Sulawesi ◽  
The Waves

Coastal area of Bitung Municipality is one of the economical activities centers in North Sulawesi Province such as for land-uses and the exploitation of natural resources. Those activities are exaggerating day bay day and tended to be uncontrollable. The excess of those conditions, it has been recorded the change of waves in Bitung waters that has impacts to coastal areas and can affect the utilization of coastal and marine resources. This research was aimed to observe waves altitude variations in Bitung waters with Svedrup Munk and Bretchsneider (SMB) method that had been used to predict waves altitudes. The results showed that the wind speed during West Season was 0.33 m and were dominant to the East, while during East season was 0.91m from South-East to North-West, and then on transition period (March to May) was 1.08m from South-East to East. The results of those wind speed to the waves altitudes in Bitung waters is discussed in this paper© Pesisir pantai Kota Bitung merupakan salah satu pusat aktivitas ekonomi (misalnya pemanfaatan lahan dan eksploitasi sumberdaya) di Provinsi Sulawesi Utara. Aktivitas tersebut semakin hari semakin meningkat dan memiliki kecenderungan tidak terkontrol. Akibat dari keadaan tersebut, telah terjadi perubahan fenomena gelombang di perairan Bitung yang berdampak pada keberadaan daerah pesisir pantai di mana hal ini dapat mengganggu aktivitas pemanfaatan sumberdaya pesisir dan laut tersebut. Penelitian ini bertujuan untuk mengetahui variasi tinggi gelombang di perairan Bitung dengan menggunakan metode Svedrup Munk and Bretchsneider (SMB) yang biasa digunakan untuk peramalan tinggi gelombang signifikan. Hasil penelitian menunjukkan bahwa kecepatan angin pada Musim Barat sebesar 0,33 meter dan dominan ke arah Timur, sementara pada Musim Timur sebesar 0,91 meter dari arah Tenggara ke Barat Laut, serta pada Musim Peralihan (antara bulan Maret-Mei) adalah sebesar 1,08 meter dari arah Tenggara dan Timur. Pengaruh kecepatan angin tersebut terhadap gelombang laut di perairan Bitung dibahas dalam tulisan ini©

Longitudinal oscillation of a rod with a variable cross section

2019 ◽  
Vol 14 (2) ◽  
pp. 138-141
Author(s):  
I.M. Utyashev
Keyword(s):  
Cross Section ◽  
Natural Frequencies ◽  
Liouville Problem ◽  
Variable Cross Section ◽  
Variable Cross ◽  
Longitudinal Vibrations ◽  
Cross Sectional ◽  
Independent Functions ◽  
The Cross ◽  
The Right

Variable cross-section rods are used in many parts and mechanisms. For example, conical rods are widely used in percussion mechanisms. The strength of such parts directly depends on the natural frequencies of longitudinal vibrations. The paper presents a method that allows numerically finding the natural frequencies of longitudinal vibrations of an elastic rod with a variable cross section. This method is based on representing the cross-sectional area as an exponential function of a polynomial of degree n. Based on this idea, it was possible to formulate the Sturm-Liouville problem with boundary conditions of the third kind. The linearly independent functions of the general solution have the form of a power series in the variables x and λ, as a result of which the order of the characteristic equation depends on the choice of the number of terms in the series. The presented approach differs from the works of other authors both in the formulation and in the solution method. In the work, a rod with a rigidly fixed left end is considered, fixing on the right end can be either free, or elastic or rigid. The first three natural frequencies for various cross-sectional profiles are given. From the analysis of the numerical results it follows that in a rigidly fixed rod with thinning in the middle part, the first natural frequency is noticeably higher than that of a conical rod. It is shown that with an increase in the rigidity of fixation at the right end, the natural frequencies increase for all cross section profiles. The results of the study can be used to solve inverse problems of restoring the cross-sectional profile from a finite set of natural frequencies.

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