Wyniki wyszukiwania - BazTech

1

Contaminant transport in the surf zone

Chin David A.

Oceanologia

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2022

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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.

2

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

Cepowski Tomasz, Kacprzak Paweł

Zeszyty Naukowe Akademii Morskiej w Szczecinie

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2019

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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.

3

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

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

International Journal of Applied Mechanics and Engineering

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2019

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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.

4

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

Drzewiecki M.

Polish Maritime Research

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2018

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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.

5

Multi-objective weather routing of sailboats considering wave resistance

Życzkowski M., Krata P., Szłapczyński R.

Polish Maritime Research

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2018

|

nr 1

4--12

EN

The article presents a method to determine the route of a sailing vessel with the aid of deterministic algorithms. The method assumes that the area in which the route is to be determined is limited and the basic input data comprise the wind vector and the speed characteristic of the vessel. Compared to previous works of the authors, the present article additionally takes into account the effect of sea waves with the resultant resistance increase on the vessel speed. This approach brings the proposed model closer to real behaviour of a sailing vessel. The result returned by the method is the sailing route, optimised based on the multi-criteria objective function. Along with the time criterion, this function also takes into account comfort of voyage and the number of performed turns. The developed method has been implemented as simulation application SaillingAssistance and experimentally verified.

6

Unbiased Total Electron Content (UTEC), their Fluctuations, and Correlation with Seismic Activity over Japan

Cornely P.-R., Hughes J.

Acta Geophysica

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2018

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Vol. 66, no. 1

51--70

EN

Earthquakes are among the most dangerous events that occur on earth and many scientists have been investigating the underlying processes that take place before earthquakes occur. These investigations are fueling efforts towards developing both single and multiple parameter earthquake forecasting methods based on earthquake precursors. One potential earthquake precursor parameter that has received significant attention within the last few years is the ionospheric total electron content (TEC). Despite its growing popularity as an earthquake precursor, TEC has been under great scrutiny because of the underlying biases associated with the process of acquiring and processing TEC data. Future work in the field will need to demonstrate our ability to acquire TEC data with the least amount of biases possible thereby preserving the integrity of the data. This paper describes a process for removing biases using raw TEC data from the standard Rinex files obtained from any global positioning satellites system. The process is based on developing an unbiased TEC (UTEC) data and model that can be more adaptable to serving as a precursor signal for earthquake forecasting. The model was used during the days and hours leading to the earthquake off the coast of Tohoku, Japan on March 11, 2011 with interesting results. The model takes advantage of the large amount of data available from the GPS Earth Observation Network of Japan to display near real-time UTEC data as the earthquake approaches and for a period of time after the earthquake occurred.

7

On wave propagation in a random micropolar generalized thermoelastic medium

Mitra M., Bhattacharyya R. K.

Archives of Thermodynamics

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2017

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Vol. 38, no. 2

21--60

EN

This paper endeavours to study aspects of wave propagation in a random generalized-thermal micropolar elastic medium. The smooth perturbation technique conformable to stochastic differential equations has been employed. Six different types of waves propagate in the random medium. The dispersion equations have been derived. The effects due to random variations of micropolar elastic and generalized thermal parameters have been computed. Randomness causes change of phase speed and attenuation of waves. Attenuation coefficients for high frequency waves have been computed. Second moment properties have been briefly discussed with application to wave propagation in the random micropolar elastic medium. Integrals involving correlation functions have been transformed to radial forms. A special type of generalized thermo-mechanical auto-correlation functions has been used to approximately compute effects of random variations of parameters. Uncoupled problem has been briefly outlined.

8

On Uncertainties in Determination of Sediment Transport Rates in Coastal Regions

Ostrowski R.

Archives of Hydro-Engineering and Environmental Mechanics

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2016

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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.

9

Influence of Nearshore Mining Pits on Hydro- and Lithodynamics of a Dissipative Coastal Zone: Case Study of the Hel Peninsula (Poland)

Ostrowski R., Skaja M.

Archives of Hydro-Engineering and Environmental Mechanics

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2016

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Vol. 63, nr 4

237--252

EN

The paper deals with a sandy shore located on the open sea side of the Hel Peninsula in Poland (the south Baltic Sea coast). The study site displays a cross-shore profile that intensively dissipates wave energy, mostly due to breaking. The theoretical modelling of wave transformation at this site reveals specific distributions of wave heights and bed shear stresses. The sediment borrow areas, presently used and identified for future exploitation, are located inconveniently far from the periodically re-nourished shores. The paper presents the possibilities of dredging works in the coastal zone that would not disturb the natural nearshore motion of water and sediments. The results of the study can be helpful in formulating generic safety standards, at least with respect to dissipative shores of non-tidal or micro-tidal seas, like the Baltic Sea.

10

Imprints of Natural Phenomena and Human Activity Observed During 10 Years of ELF Magnetic Measurements at the Hylaty Geophysical Station in Poland

Nieckarz Z.

Acta Geophysica

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2016

|

Vol. 64, no. 6

2591--2608

EN

Current human activity produces strong electromagnetic pollution. The power spectrum in the extremely low frequency (ELF, 3-3000 Hz) range is mainly polluted by anthropogenic narrow spectral lines at 16.66, 50, and 60 Hz and their harmonics. Meanwhile, signatures connected with natural phenomena appearing in the Earth’s atmosphere, ionosphere and magnetosphere are also observed in the same frequency range. This paper presents the amplitude behaviour of the anthropogenic lines in the years 2005-2014 based on the 10 years of activity of the Hylaty station situated in southeast Poland. The analysis includes, i.a., an assessment of the correctness of the choice of the Bieszczady mountains as a location for the installation of an ELF station for long-term geophysical and climatological studies.

11

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

Szelangiewicz T., Żelazny K.

Zeszyty Naukowe Akademii Morskiej w Szczecinie

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2015

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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.

12

Variableloading conditions and consequences for wave phenomena

Bogacz B., Frischmuth K., Konowrocki R.

TTS Technika Transportu Szynowego

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2015

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R. 22, nr 12

168--171, CD

EN

In land transport, we observe an increase of loads as well as of speeds of travel, which leads to considerable stresses and strains in constructions like tracks, bridges and tunnels. The wave propagation caused by constant and harmonic loads moving at constant speed along straight lines has been well covered in the recent literature. Problems including other types of variable loading conditions are much less understood. In the article, some problems of this type are posed and discussed together with applications in vehicle mechanics. In particular, motion of out-of-the-round wheels on rails and some problems of brake disk dynamics are presented.

PL

W transporcie lądowym, zwłaszcza szynowym, obserwuje się tendencję do coraz wyższych prędkości i większych obciążeń, skąd wynikają między innymi znaczne naprężenia wtakich konstrukcjach jak szyny, mosty i tunele.Efekty falowe z tym związane dobrze są zbadane w przypadku stałych prędkości ruchu prostolinijnego i harmonicznych obciążeń. Zagadnienia uwzględniające innego typu zmienności sił czy warun-ków brzegowych dotąd nie znalazły odpowiednio dużo uwagi w literaturze. W obecnej pracy kilka zadań tej klasy zostało postawionych i przedyskutowanych, między innymi problem związany z kołami skorugowanymi i problem dynamiki dysku hamulcowego jako przykłady z zakresu mechaniki pojazdów szynowych.

13

Walking the Line. Traveling Forces vs Moving Masses

Bogacz R., Frischmuth K., Konowrocki R.

Symulacja w Badaniach i Rozwoju

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2015

|

Vol. 6, nr 3

165--173

EN

In railway mechanics, and more general, in civil engineering and vehicle dynamics, the problem of simultaneous modeling of a track and a vehicle has been the subject of many papers. Often one of the coupled subsystems is highly simplified in order to be able to obtain results on the other. For example, when the propagation of waves in the track is the main concern, vehicles such as a train or a taxiing airplane, are treated as an external force, travelling at a certain speed along a given path. In that case, the force is assumed as independent of the motion in the track, which results from the load. On the other hand, dynamical simulations of vehicles typically run on a defined ground, which is given and invariant, whatever the motion of the vehicle. In order to make a track model more realistic, the vehicle model may be improved, without going as far as to couple a full-fledged vehicle model with a realistic model of a track consisting of rails on sleepers, supported via some subgrade on the ground. A first simple step is to attach an additional mass in the contact point, i.e. the position, where the external force is applied.

PL

W inżynierii kolejowej lub ogólniej - w budownictwie i dynamice pojazdów zagadnienie równoczesnego modelowania toru i pojazdu było przedmiotem wielu badań. Często jeden ze sprzężonych układów był nadmiernie upraszczany, aby uzyskać rozwiązanie problemu. Zagadnienie struny najczęściej rozpatruje się w zakresie małych przesunięć i kątów, poszukiwana jest wówczas funkcja skalarna jednej zmiennej. Gdy konfiguracja aktualna odbiega znacznie od konfiguracji materialnej, wyniki uzyskane mogą być fizycznie nieakceptowalne. W pracy do rozwiązywania tego typu zadań zaleca się podejście parametryczne. Zalety takiego podejścia demonstrowane są na podanych przykładach z zakresu modelowania współpracy pojazdu z trakcją oraz popularnych sportów rekreacyjnych.

14

Teoria głębokości zamknięcia w świetle pomiarów terenowych na wielorewowym brzegu morskim

Cerkowniak G. R., Ostrowski R., Pruszak Z., Skaja M., Stella M.

Inżynieria Morska i Geotechnika

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2015

|

nr 1

10—17

PL

Koncepcja głębokości zamknięcia. Wyznaczenie odmorskiego zasięgu zmian dennych w oparciu o ekstremalne roczne parametry falowe. Weryfikacja teoretycznego pojęcia na podstawie danych terenowych zebranych w rejonie Morskiego Laboratorium Brzegowego IBW PAN w Lubiatowie. Hipoteza dotycząca znacznego wpływu prądów typowych dla pełnego morza, występujących poza strefą brzegową.

EN

Depth of closure concept. Determination of the offshore range of sea bottom changes by the extreme annual wave parameters. Verification of this theoretical notion by the field data collected at the IBW PAN Coastal Research Station in Lubiatowo. Hypothesis on significant influence of the currents typical for the open sea, beyond the coastal zone.

15

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

Cepowski T.

Zeszyty Naukowe / Akademia Morska w Szczecinie

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2014

|

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.

16

Formation and species composition of stormcast beach wrack in the Gulf of Riga, Baltic Sea

Suursaar Ű., Torn K., Martin G., Herkül K., Kullas T.

Oceanologia

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2014

|

No. 56 (4)

673--695

EN

The aim of the study was to investigate hydrodynamic effects on the formation of beach wrack at three locations in the northern Baltic Sea and to quantify the differences between the composition of species found in the beach wrack and in the neighbouring sea. Hydrodynamic measurements and modelling indicated that the beach wrack was mostly of local origin and that it was formed during high sea level and wave events. Comparison of the methods of beach wrack sampling and seabed sampling (diver, underwater video) demonstrated that beach wrack sampling can be considered an alternative tool for describing the species composition of macrovegetation in near-coastal sea areas. Although the hydrodynamic variability is greater in autumn and more biological material is cast ashore, the similarity between the two sampling methods was higher in spring and summer.

17

Propagation of surface water waves in the presence of current – analysis of measurements carried out in the wave flume of the IBW PAN

Stachurska B., Majewski D.

Inżynieria Morska i Geotechnika

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2014

|

nr 4

280--290

PL

Eksperymentalne badania współoddziaływania fal powierzchniowych w obecności prądu wodnego. Zależności pomiędzy kierunkiem i prędkością prądu a okresem fali. Ich wpływ na zmiany w wychyleniu powierzchni swobodnej oraz na amplitudy prędkości przepływu.

EN

Experimental study of interaction of surface water waves with currents, conducted for the first time in Poland. The relationship between the current direction, current velocity and the period of the wave. Its effect on free surface elevation and on the current velocity amplitude.

18

Eksperymentalne wyznaczanie obciążeń ścian zbiorników okrętowych podczas falowania

Trębacki K.

TTS Technika Transportu Szynowego

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2012

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R. 19, nr 9

2095--2104, CD

PL

W artykule przedstawiono wyniki badań eksperymentalnych, dotyczących współoddziaływania konstrukcji zbiornika z cieczą. Analiza ta dotyczy badań modelowych. Badanie tego zjawiska ma odniesienie do często spotykanych zdarzeń praktycznych, jak zderzenie zbiornikowca z innym statkiem lub nabrzeżem portowym, gwałtowne hamowanie cystern samochodowych lub kolejowych itp. Rozpoznanie zjawiska doprowadziło do jednoczesnych pomiarów następujących wielkości: a) wymuszanych amplitud układu generator-ciecz b) ciśnień hydrodynamicznych na ścianie zbiornika c) kształtu powierzchni swobodnych d) rozkładu prędkości cieczy w pobliżu ścianki.

EN

The article presents The results of experimental investigations of interactions between structure tank and a liquid. The analysis is based on modelling research. The investigation of this phenomenon has direct reference to frequently recorded real events, such as collision of a tanker with another ship ora a harbour berth, rapid braking of a road or rail tanker, etc. Recognition of this phenomenon is based on simultaneous measurements of the following parameters: a) excited amplitudes of the generator-liquid system b) hydrodynamic pressures on the wall tank c) elevation of the free surface d) distribution of the velocity of water particles around the tank surface.

19

Wind influence on the formation of nearshore currents in the southern Baltic: mumerical modelling results

Sokolov A., Chubarenko B.

Archives of Hydro-Engineering and Environmental Mechanics

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2012

|

Vol. 59, nr 1-2

37-48

EN

A two-dimensional numerical model was used for a simulation of vertical average longshore currents generated by both wind friction and wind-wave action in the nearshore zone. The modelling domain includes the southern part of the Baltic Proper (all boundaries were closed). Wind, uniform in space and varying in time, was the only forcing in the model. The correlation coefficient higher than 0.8 was obtained by model calibration versus the field measurements of currents conducted at the Lubiatowo field station (southern Baltic) during about 1.5 months in 2006. Comparative simulations of total currents including both wind-induced drift and wave components, and of total currents including only a wind-induced drift component, showed that the input of the drift component into currents in the nearshore zone is greater than commonly believed. Wind-induced drift strongly dominates outside the zone of wave transformation, and its input into the total resulting currents remains noticeable even in a zone between the shoreline and the depth of the first wave breaking. Thus, wind-induced drift constitutes up to 50% of the resulting longshore currents for longshore winds and no less than 20% of the longshore component of currents for winds at 45 degrees to the longshore direction.

20

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

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

Oceanologia

|

2011

|

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.