Wyniki wyszukiwania - Biblioteka Nauki

1

The propagation of the waves in the CTO S.A. towing tank

100%

Drzewiecki M.

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tom S 1

22--28

EN

The paper presents the results of research focused on the wave propagation in the CTO S.A. deepwater towing tank. In the scope of paper, the wavemaker transfer function was determined for regular waves, based on the Biésel Transfer Function and further for irregular waves, based on Hasselman model of nonlinear energy transfer. The phenomena: wave damping, wave breakdown and wave reflection, were measured, analyzed and mathematically modeled. Developed mathematical models allow to calculate the impact of mentioned phenomena on the wave propagation and furthermore to calculate the wave characteristics along the whole measurement area in the CTO S.A. deepwater towing tank, based on wavemaker flap motion control.

2

Contaminant transport in the surf zone

100%

Chin D. A.

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2022

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tom No. 64 (4)

651--664

EN

Dispersion of dissolved contaminants introduced at various locations within and just outside the surf zone are investigated. It is shown that the Longuet-Higgins model of surf-zone hydrodynamics adequately describes the distribution of longshore currents measured at the laboratory scale. Relations are derived between the longitudinal and transverse dispersion coefficients and the influencing parameters. The maximum longitudinal dispersion coefficients are associated with tracer releases near the breaker line, and longitudinal dispersion coefficients generally increase with travel time for distances up to at least 10 surf-zone widths. In contrast, transverse dispersion coefficients remain relatively constant for increasing travel time. The longitudinal and transverse dispersion coefficients can be significantly influenced by assumed values of local turbulent diffusion and cross-shore shear dispersion.

3

On Uncertainties in Determination of Sediment Transport Rates in Coastal Regions

88%

Ostrowski R.

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tom Vol. 63, nr 4

265--280

EN

The paper deals with research uncertainties, difficulties, inaccuracies and unreliabilities related to the modelling of physical phenomena involving coastal lithodynamics. The considerations are focused on processes of wave transformation, wave-driven currents and sediment transport itself. It is shown that possible inaccuracies at individual stages of the modelling of coastal hydrodynamics can lead to serious uncertainties with respect to the ultimate modelling output, namely bed shear stresses and sediment transport rates. These inaccuracies result mostly from arbitrarily assumed parameters and constants. Other modelling biases discussed in the paper comprise simplifications and approximations with respect to sediment resources and size-graded properties, randomness of hydrodynamic impacts, bottom roughness and land-borne factors involved in coastal lithodynamics.

4

Flow, waves and water exchange in the Suur Strait, Gulf of Riga, in 2008

75%

Raudsepp U. , Laanemets J. , Haran G. , Alari V. , Pavelson J. , Köuts T.

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tom No. 53 (1)

35-56

EN

Wind, flow and wave measurements were performed in November-December in 2008 in the relatively narrow and shallow Suur Strait connecting the waters of the Väinameri and the Gulf of Riga. During the measurement period wind conditions were extremely variable, including a severe storm on 23 November. The flow speed along the strait varied between ±0.2 m s-1, except for the 0.4 m s-1 that occurred after the storm as a result of the sea level gradient. The mean and maximum significant wave heights were 0.53 m and 1.6 m respectively. Because of their longer fetch, southerly winds generated higher waves in the strait than winds from the north. All wave events caused by the stronger southerly winds induced sediment resuspension, whereas the current-induced shear velocity slightly exceeded the critical value for resuspension only when the current speed was 0.4 m s-1. A triple-nested two-dimensional high resolution (100 m in the Suur Strait) circulation model and the SWAN wave model were used to simulate water exchange in 2008 and the wave-induced shear velocity field in the Suur Strait respectively. Circulation model simulations demonstrated that water exchange was highly variable, that cumulative transport followed an evident seasonal cycle, and that there was an gross annual outflow of 23 km3 from the Gulf of Riga. The horizontal distribution of wave-induced shear velocity during the strong southerly wind event indicated large shear velocities and substantial horizontal variability. The shear velocities were less than the critical value for resuspension in the deep area of the Suur Strait.

5

An analysis of vertical shear forces and bending moments during nodule loading for a standard bulk carrier in the Clarion-Clipperton Zone

75%

Cepowski T. , Kacprzak P.

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2019

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tom nr 60 (132)

184--191

EN

This article presents an analysis of vertical shear forces and bending moments during nodule loading in the case of a standard bulk carrier around the Clarion–Clipperton Zone. An operational efficiency index was applied to an assessment of internal forces during loading which took into account wave heights and periods around this zone. The aim of this research was to investigate whether waves could have a negative effect on loading efficiency and to estimate the nodule mass that can safely be loaded onto a standard bulk carrier taking these waves into account. Moreover, a calculation was made to discover the acceptable vertical shear force percentage limit, while also taking into account wave activity during loading.

6

Vibrations and waves in a fibre-reinforced composite

75%

Augustowska L. , Siedlecka U. , Wierzbicki E.

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tom Vol. 20

86--87

7

Metoda wyznaczania linii ugięcia kadłuba okrętu

75%

Pawlędzio A.

Zeszyty Naukowe Akademii Marynarki Wojennej

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2006

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tom R. 47 nr 2 (165)

75-88

PL

W niniejszym opracowaniu rozpatruje się zagadnienie wyznaczenia linii ugięcia kadłuba okrętu na wodzie spokojnej oraz na fali. Obliczenia testowe przeprowadzono dla zamkniętego odcinka rury, a następnie po zweryfikowaniu numerycznej metody obliczeniowej z rozwiązaniem analitycznym dla okrętu typu 207M. Opisywane rozwiązanie bazuje na metodzie elementów skoń-czonych [2]. Przyjęty model belkowy konstrukcji kadłuba okrętu składa się z dwudziestu elemen-tów o stałej długości.

EN

The paper presents the method for determining the line of ship’s hull. Test computations were carried out for a closed section of a tube and then, after verifying the numerical computation method with the analytical solution, for the ship type 207M. The calculating process described is based on the finite element method. The adopted beam model of ship’s hull consists of 20 ele-ments of constant length.

8

Interfacial instabilities and wave effect on the transfer processes

75%

Alekseenko S. , Aktershev S. , Markovich D.

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1999

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tom Z. 67

13--22

EN

This paper contains a review of the results which have been obtained by the authors during last several years and concerned with the development of two- and three-dimensional waves on falling liquid films as well as on rivulets flowing down on the lower side of inclined cylinder. Also the theoretical modelling of the stability of the liquid films with presence of turbulent gas flow is described and experimental results on the wave effect on the transfer processes are presented.

9

An approximate method for calculating total ship resistance on a given shipping route under statistical weather conditions and its application in the initial design of container ships

75%

Szelangiewicz T. , Żelazny K.

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tom nr 44 (116)

99--106

EN

During ship design, its service speed is one of the crucial parameters that determine its future operational profitability. As sufficiently exact calculation methods applicable to preliminary design stage are lacking, the so-called contract speed, the speed a ship reaches in calm water, is usually specified during the draft stage. The service speed obtainable by a ship under real weather conditions (mainly wind and waves) is one of the most important parameters influencing a ship’s profitability on a given shipping route. This paper presents a parametric model of calculating total ship resistance on a given shipping route under actual weather conditions (wind, waves, sea current), that could be useful in the initial design of container ships.

10

The influence of ship's motion in regular wave on dynamics of an offshore crane.

63%

Osiński M. , Maczyński A. , Wojciech S.

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tom Vol. LI, nr 2

131-163

EN

The paper presents the numerical model of a supply vessel-load-crane-offshore vessel system for simulation of heave motion and dynamic analysis of the system during critical phases of the handing operation: taking the load off from and lowering it to a moving base. The model enables extreme forces in elements and deflection of the structure to be determined. Different operating and emergency conditions can be simulated (e.g. horizontal motion of a supply vessel). The elaborated software can be applied also for determination of derated load charts and ultimate crane capacity (sequence of failure).

PL

W pracy przedstawiono model matematyczny układu statek dostawczy-ładunek-żuraw-statek przeznaczony do symulacji ruchu oraz analizy dynamicznej układu podczas krytycznych faz operacji przeładunku ładunku, tj. jego podnoszenia lub posadawiania na ruchomym pokładzie jednotki dostawczej. Żurawie pracujące w warunkach offshore podane są między innymi obciążeniom wynikającym z ruchu zarówno bazy żurawia (statek bazowy, platforma) jak również ruchu jednostki dostawczej wywołanych falowaniem morskim. Na etapie projektowania żurawia niezbędne jest określenie sekwencji zniszczenia poszczególnych elementów (crane failure chart). Opracowany model umożliwia zarówno wyznaczenie maksymalnych sił wewnętrznych i odkształceń elementów układu, jak również symulowanie różnych stanów awaryjnych, np. wywołanych nagłą zmianą położenia jednostki względem żurawia. Opracowano model i program obliczeniowy wykorzystywany jest przy projektowaniu nowych i modernizacji istniejących żurawi typu offshore. W artykule zaprezentowano wyniki obliczeń dla przypadku gdy ruch unoszenia statku jest ruchem nurzania.

11

The progress in knowledge of physical oceanography of the Gulf of Finland: a review for 1997-2007

63%

Soomere T. , Myrberg K. , Leppäranta M. , Nekrasov A.

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tom No. 50 (3)

287-362

EN

The main findings of studies of the physical oceanography of the Gulf of Finland (GoF) during 1997-2007 are reviewed. The aim is to discuss relevant updates published in international peer-reviewed research papers and monographs, bearing in mind that a comprehensive overview of the studies up to the mid-1990s is available (Alenius et al. 1998). We start the discussion with updates on the basic hydrographical and stratification conditions, and progress in the understanding of atmospheric forcing and air-sea interaction. Advances in the knowledge of basin-scale and mesoscale dynamics are summarised next. Progress in circulation and water exchange dynamics has been achieved mostly by means of numerical studies. While the basic properties of circulation patterns in the gulf have been known for a century, new characteristics and tools such as water age, renewal index, and high-resolution simulations have substantially enriched our knowledge of processes in the Gulf of Finland during the last decade. We present the first overview of both status and advances in optical studies in this area. Awareness in this discipline has been significantly improved as a result of in situ measurements. Our understanding of the short- and long-term behaviour of the sea level as well as knowledge of the properties of both naturally and anthropogenically induced surface waves have expanded considerably during these ten years. Developments in understanding the ice conditions of the Gulf of Finland complete the overview, together with a short discussion of the gulf's future, including the response to climate change. Suggestions for future work are outlined.

12

Longitudinal strength problems in design of ships for loading nodules at sea

63%

Cepowski T.

Zeszyty Naukowe / Akademia Morska w Szczecinie

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2014

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tom nr 39 (111)

53--56

EN

The naval architect has to tackle many of the problems, while designing ships for the loading, storage and transport of polymetallic or other nodules, this article focuses on how to assure appropriate hull strength. This author proposes mathematical relationships and operational and design solutions allowing to more effectively reduce shear forces and bending moments during the loading of nodules in the open sea. The suggested solutions may be used in the design of ships intended for such or other functions.

13

Plane waves in thermo-viscoelastic material with voids under different theories of thermoelasticity

63%

Tomar S. K. , Goyal N. , Szekeres A.

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tom Vol. 24, no. 3

691--708

EN

Propagation of time harmonic plane waves in an infinite thermo-viscoelastic material with voids has been investigated within the context of different theories of thermoelasticity. The equations of motion developed by Iesan [1] have been extended to incorporate the Lord-Shulman theory (LST) and Green-Lindsay theory (GLT) of thermoelasticity. It has been shown that there exist three coupled dilatational waves and an uncoupled shear wave propagating with distinct speeds. The presence of thermal, viscosity and voids parameters is responsible for the coupling among dilatational waves. All the existing waves are found to be dispersive and attenuated in nature. The phase speeds and attenuation coefficients of propagating waves are computed numerically for a copper material and compared under different theories of thermo-elasticity. The expressions of energies carried along each wave have also been derived. All the computed numerical results have been depicted through graphs. It is found that the influence of CT and GLT is almost same on wave propagation, while LST influences the wave propagation differently.

14

Wave propagation at the boundary surface of orthotropic porous material with rotation and isotropic elastic half-space

51%

Kumar R. , Kumar R.

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tom Vol. 16, no 3

683-708

EN

The purpose of this research is to study the surface wave propagation in a layer of an orthotropic porous material with rotation lying over an isotropic elastic half-space. The frequency equation is derived after developing the mathematical model. The dispersion curves giving the phase velocity and attenuation coefficient versus wave number are plotted graphically to depict the effects of rotation and anisotropy for (I) welded contact and (II) smooth contact boundary conditions. The amplitudes of normal displacement, normal stress, volume fraction field and gradient of volume fraction field for the welded contact are obtained and are shown graphically for a particular model to depict the rotation and anisotropy effects. Some special cases are also deduced from the present investigation.