Wyniki wyszukiwania - Biblioteka Nauki

1

Effect of seepage on initiation of cohesionless sediment transport

100%

Liu X. , Chiew Y.-M.

Acta Geophysica

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2012

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tom Vol. 60, no. 6

1778-1796

EN

This paper presents theoretical analyses and experimental results of seepage effects, especially downward seepage, on the initiation of cohesionless sediment particles. The theoretical analysis examines how the additional seepage force acts to modify the critical shear stress for sediment entrainment. Laboratory experiments were conducted using medium sand with diameter of 0.9 mm with downward seepage to quantitatively show suction effects on sediment entrainment. The critical shear stresses with different suction rates were calculated using the experimental results. The measured data together with published results provide an overall view on seepage effects on the initiation of cohesionless sediment transport. Depending on whether seepage is in the form of injection or suction, it will either increase or decrease the critical shear stress. The result reveals that the ratio of drag force at the threshold condition with seepage to that without seepage is dependent on the ratio of the hydraulic gradient with seepage to its value at the quick condition.

2

Podstawy modelowania transportu osadów

100%

Kaczmarek L. M.

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2012

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tom nr 1

19-24

PL

Krytyczne uwagi dotyczące podstawowych tez zaprezentowanych w artykule A. Sawickego „O elementarnym modelowaniu transportu osadów”opublikowanym w nr 5/2011 „Inżynierii Morskiej i Geotechniki”. Formalna analiza problemu transportu osadów.

EN

Critical comments regarding basic theses included in the paper of A. Sawicki entitled „On elementary modelling of sediment transport” published in „Inżynieria Morska i Geotechnika”, No.5/2011. Formal analysis of sediment transport problem.

3

Double-average characteristics of sediment motion in one-dimensional bed load

100%

Radice A. , Ballio F.

Acta Geophysica

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2008

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tom Vol. 56, no. 3

654-668

EN

The sediment transport process on a flat bed was investigated experimentally, with reference to the relationship between the average solid discharge and the concentration and velocity of the moving grains. The instantaneous values of the quantities were measured and, therefore, it was possible to quantify the contribution of the temporal fluctuations of concentration and velocity to the resulting average sediment transport rate. Recognizing that the sediment transport process is an episodic phenomenon, an intermittency factor was defined and its contribution to the solid discharge, typically implicit in earlier formulations of the sediment flux, was highlighted. Conceptual analyses of the spatial scale dependence of the quantities were also made.

4

Bed load transport by bed form migration

88%

Aberle J. , Coleman S. , Nikora V.

Acta Geophysica

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2012

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tom Vol. 60, no. 6

1720-1743

EN

A theoretically-based methodology is presented for the determination of bed load transport from high-resolution measurements of bed surface elevations for steady-state or developing dunes. The methodology is based on the general form of the Exner equation for sediment continuity and requires information on the distribution of sediment volume concentration as well as the migration velocity of bed layers. In order to determine layer speeds, a new method based on cross-correlation analysis of elevation slices is proposed. The methodology is tested using artificiallycreated data as well as data from a physical model and from a flume study of developing bed forms. The analyses show the applicability of the method to determine bed load transport without the need to introduce assumptions about the form of the migrating surface. It is shown that predicted transport rates match measured or theoretical transport rates for steadily moving bed forms of an arbitrary shape. The method can also be used to predict transport rates over deforming bed forms, with the reasons for potential deviations between predicted and measured or theoretical transport rates for deforming bed forms identified and discussed. It is further shown that a simplified bulk-surface approach, that is relatively straightforward to apply and in which it is assumed that bed-layer velocity is constant with depth, gives results that are comparable to analyses based on determined bed-layer velocity variation with depth.

5

Towards validating a last generation, integrated wave-current-sediment numerical model in coastal regions using video measurements

88%

Carniel S. , Sclavo M. , Archetti R.

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2011

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tom Vol. 40, No.4

11-20

EN

This paper presents the first steps in the implementation of a morphological numerical model to be applied in the Bevano River region, a shallow water area in the Adriatic Sea, with the aim of helping the identification and assessment of erosional patterns and bottom morphological modifications induced by severe marine storms. The numerical modeling, performed using a fully 3D coupled wave-current-sediment version of the ROMS model, has been complemented with in situ data analysis and observations: a first qualitative validation of the results was given by the analysis of images acquired via an ARGUS video station. Hydrodynamic modeling highlighted how shear bottom stresses and bottom currents fields were heavily influenced by severe storm situations, and had large effects on the morphology of shallow regions. The correlation between the wave-current induced bottom stresses and the resulting topography was investigated. Nearshore hydrodynamics modeling results demonstrated the dominant role played by alongshore sediment transport, with the magnitude of both cross- and along-shore wave-induced currents strongly depending on wave height and direction. We found a good qualitative conformity between the results of the numerical models applied during a "Bora" storm and the corresponding video observations; both techniques indicated the migration of the existing sandbar within the range of about 40 m seaward. Results show how integrated numerical open source tools, often used in oceanography, are becoming suitable for both preliminary investigations and for planning the effective littoral management, and how their calibration can be supported by the use of new low cost techniques, such as video measurements.

6

Longshore sediment transport at Golden Sands (Bulgaria)

88%

Nikolov H. , Trifonova E. , Cherneva Z. , Ostrowski R. , Skaja M. , Szmytkiewicz M.

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2006

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tom No. 48 (3)

413-432

EN

The paper presents the results of studies on the qualitative and quantitative features of the littoral drift at Golden Sands (Bulgaria), carried out jointly by Polish and Bulgarian researchers. The mathematical modelling of physical coastal processes took wave transformation (wave diffraction and refraction; the effects of shoaling and wave breaking) and longshore sediment transport into account. The computations were carried out for the mean statistical annual wave climate, determined on the basis of IO BAS wave data, simulated using the WAM method from long-term Black Sea wind data. The results of sediment transport computations clearly show that its direction off the Golden Sands shore is from north to south.

7

Błędy przy modelowaniu transportu osadów

88%

Sawicki A.

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2012

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tom nr 3

199-200

PL

Dyskusja nad podstawowymi błędami wynikającymi z nieprawidłowego stosowania matematyki i mechaniki zamieszczonymi w artykule [2] dotyczącym modelowania transportu osadów.

EN

Discussion on the fundamental errors resulting from incorrect application of math and mechanics contained in paper [2] regarding the modeling of sediment transport.

8

3D Lagrangian modelling of saltating particles diffusion in turbulent water flow

75%

Bialik R. , Nikora V. , Rowiński P.

Acta Geophysica

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2012

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tom Vol. 60, no. 6

1639-1660

EN

A 3D Lagrangian model of the saltation of solid spherical particles on the bed of an open channel flow, accounting for turbulence-induced mechanisms, is proposed and employed as the key tool of the study. The differences between conventional 2D models and a proposed 3D saltation model are discussed and the advantages of the 3D model are highlighted. Particularly, the 3D model includes a special procedure allowing generation of 3D flow velocity fields. This procedure is based on the assumption that the spectra of streamwise, vertical and transverse velocity components are known at any distance from the bed. The 3D model was used to identify and quantify effects of turbulence on particle entrainment and saltation. The analysis of particle trajectories focused on their diffusive nature, clarifying: (i) the effect of particle mobility parameter; (ii) the effect of bed topography; and (iii) the effect of turbulence. Specifically, the results of numerical simulations describing the abovementioned effects on the change in time of the variance are presented. In addition, the change in time of the skewness and kurtosis, which are likely to reflect the turbulence influence on the spread of particles, are also shown. Two different diffusion regimes (local and intermediate) for each of the investigated flow conditions are confidently identified.

9

Scale-based statistical analysis of sediment fluxes

75%

Campagnol J. , Radice A. , Ballio F.

Acta Geophysica

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2012

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tom Vol. 60, no. 6

1744-1777

EN

The flux of sediments over a line perpendicular to the main flow direction was measured during experiments of weak one-dimensional bed load. The standard definition of solid discharge through a boundary is a straightforward issue, yet the dependence of resulting values on the spatial and temporal scales used as a support for measurement is not. In this work, first- and second-order statistics of sediment transport rates were analyzed as scale-dependent quantities. The spatial scales used were significantly larger than the particle size, while the temporal scales covered a two-orders-of-magnitude range enabling the physical time scales of the single particles to be appreciated. In addition, the relationship between sediment fluxes, process intermittency and particle interarrival times was investigated. Proper knowledge of the scaledependence of statistical properties of sediment transport fluxes may allow for adequate design of measuring campaigns (both in the laboratory and field) and for sound interpretation of data from multiple sources.

10

Sediment transport mechanics

75%

Ballio F. , Tait S.

Acta Geophysica

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2012

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tom Vol. 60, no. 6

1493-1499

EN

The Editor of Acta Geophysica and the Guest Editors wish to dedicate this Topical Issue on Sediment Transport Mechanics to the memory of Stephen Coleman, who died recently. During his career, Stephen had made an outstanding scientific contribution to the topic of Sediment Transport. The level of his contribution is demonstrated in the paper by Aberle, Coleman, and Nikora included in this issue, on which he started working before becoming aware of the illness that led to his untimely death. For scholars and colleagues Stephen remains an example of intellectual honesty and scientific insight.

11

Turbulence in mobile-bed streams

75%

Dey S. , Das R. , Gaudio R. , Bose S.

Acta Geophysica

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2012

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tom Vol. 60, no. 6

1547-1588

EN

This study is devoted to quantify the near-bed turbulence parameters in mobile-bed flows with bed-load transport. A reduction in near-bed velocity fluctuations due to the decrease of flow velocity relative to particle velocity of the transporting particles results in an excessive near-bed damping in Reynolds shear stress (RSS) distributions. The bed particles are associated with the momentum provided from the flow to maintain their motion overcoming the bed resistance. It leads to a reduction in RSS magnitude over the entire flow depth. In the logarithmic law, the von Karman coefficient decreases in presence of bed-load transport. The turbulent kinetic energy budget reveals that for the bed-load transport, the pressure energy diffusion rate near the bed changes sharply to a negative magnitude, implying a gain in turbulence production. According to the quadrant analysis, sweep events in mobile-bed flows are the principal mechanism of bed-load transport. The universal probability density functions for turbulence parameters given by Bose and Dey have been successfully applied in mobile-bed flows.

12

Motion of water and sediment due to non-breaking waves in the swash zone

75%

Kapiński J. , Ostrowski R.

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2012

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tom No. 54 (2)

175-197

EN

A long wave run-up theory is applied to the modelling of wave-induced flow velocities, sediment transport rates and bottom changes in a swash zone. First, the properties of the water tongue motion and the resulting lithodynamic response are analysed theoretically. Next, an attempt is made to run the model for the natural conditions encountered on the southern Baltic Sea coast. The Lagrangian swash velocities are used to determine the Eulerian phase-resolved bed shear stresses with a momentum integral method, after which the motion of sand is described by the use of a two-layer model, comprising bedload and nearbed suspended load. Seabed evolution is then found from the spatial variability of the net sediment transport rates. The results presented are limited to cases of the small-amplitude waves that seem to be responsible for accretion on beaches.

13

Trójwarstwowy model transportu osadów niejednorodnych w rzekach oraz wybrane przykłady jego weryfikacji

75%

Kaczmarek L. M. , Sobczak Ł. , Biegowski J.

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2010

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tom nr 4

493-501

PL

Transport rumowiska a zmiany morfologiczne koryta rzeki w czasie i przestrzeni. Trójwarstwowy model matematyczny transportu i segregacji osadów piaszczystych w rzekach. Weryfikacja modelu trójwarstwowego na podstawie porównania wyników obliczeń z innymi formułami oraz z danymi zarejestrowanymi in-situ na rzece Wiśle i Redzie. Podsumowanie.

EN

Sediment transport versus morphological changes of river bed in time and space. Three-layered mathematical model of transport and segregation of sandy sediments in rivers. Verification of the model based on comparison of calculation results with other formulae and filed data taken from Vistula and Reda rivers. Summary.

14

Modelling of the silting up processes in water routes of Łeba and Tolkmicko ports

63%

Kaczmarek L. M. , Sawczyński S.

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2008

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tom nr 11

161-174

EN

A theoretical three-layer model of non-uniformly graded sediment transport has been used to analyse the silting up of water routes in the port of Łeba and Tolkmicko. Comparison of the results derived from model calculations with the measurements and dredging work data has demonstrated that the model is useful for prediction of the silting up extent as well as the distribution of grain-size fractions in sediments captured in water routes of ports, which are different in bathymetric as well as hydrodynamic parameters, and where sea bottom deposits are different in nature.

PL

Do analizy zapiaszczania torów wodnych portów w Łebie i Tolkmicku wykorzystano trójwarstwowy model teoretyczny transportu osadów niejednorodnych granulometrycznie. Porównanie wyników obliczeń z pomiarami i wielkościami robót czerpalnych wykazało przydatność modelu do predykcji zarówno wielkości zapiaszczania, jak i rozkładów uziarnienia osadów zatrzymywanych w torach portów o różnych reżimach batymetryczno-hydrodynamicznych oraz różnym charakterze osadów budujących dno morskie.

15

Analysis of sediment particle velocity in wave motion based on wave flume experiments

63%

Krupiński A.

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2012

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tom Vol. 34, nr 2

41-50

EN

The experiment described was one of the elements of research into sediment transport conducted by the Division of Geotechnics of West-Pomeranian University of Technology. The experimental analyses were performed within the framework of the project "Building a knowledge transfer network on the directions and perspectives of developing wave laboratory and in situ research using innovative research equipment" launched by the Institute of Hydroengineering of the Polish Academy of Sciences in Gdańsk. The objective of the experiment was to determine relations between sediment transport and wave motion parameters and then use the obtained results to modify formulas defining sediment transport in rivers, like Ackers-White formula, by introducing basic parameters of wave motion as the force generating bed material transport. The article presents selected results of the experiment concerning sediment velocity field analysis conducted for different parameters of wave motion. The velocity vectors of particles suspended in water were measured with a Particle Image Velocimetry (PIV) apparatus registering suspended particles in a measurement flume by producing a series of laser pulses and analysing their displacement with a high-sensitivity camera connected to a computer. The article presents velocity fields of suspended bed material particles measured in the longitudinal section of the wave flume and their comparison with water velocity profiles calculated for the definite wave parameters. The results presented will be used in further research for relating parameters essential for the description of monochromatic wave motion to basic sediment transport parameters and "transforming" mean velocity and dynamic velocity in steady motion to mean wave front velocity and dynamic velocity in wave motion for a single wave.

16

Appraise of consequences of erosive processes occurring in the Skawa river sector

51%

Bąk Ł. , Michalik A. , Tekielak T.

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2011

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tom Vol. 37, nr 1

83-92

EN

Erosive processes have been evaluated in a sector of the Skawa river characterized by high pliability to erosion (proportion between the bend radius and the river channel width equals on the average 6.5). Within two years, channel erosion caused by 6 freshets was investigated with flows Q within the range of probability of waters from 20% to 50%. Bank and bottom erosion as well as transportation of the bed material and material from falls of bank slopes were found to occur. Intensity of this transportation was calculated based on Bagnold's equation. The calculated value of transported bed load was comparable with that obtained from direct measurements. The effects of transportation were also reflected by changes of the grain size distributions after passage of a freshet wave. Bank erosion was the dominating process that changed the river channel shape. It was found that in the examined sector the retreat of the bank slope proceeded at the rate of 1.20 m/year.

17

Hydro- and Lithodynamic Aspects of Constructing a Navigable Canal Through the Vistula Spit

44%

Kaczmarek L. M.

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2009

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tom nr 12

40-56

EN

The paper presents hydro- and lithodynamic aspects of the intended construction of a navigable canal across the Vistula Spit. The discussion is based on the results of a study funded by a research and development grant carried out in 2007/2008 at the Institute of Hydro-Engineering of the Polish Academy of Sciences in Gdańsk in collaboration with the Chair of Civil Engineering and Building Constructions, Faculty of Technical Sciences, the University of Warmia and Mazury in Olsztyn. The paper also contains an analysis of the effect of planned breakwaters protecting the entrance to the canal from the Gulf of Gdańsk on the seaward shores of the Vistula Lagoon and the effect of their length on the silting up of the fairway. Some recommendations have been suggested regarding the optimal length of planned breakwaters.

PL

W artykule przedstawiono aspekty hydro- i litodynamiczne planowanej budowy kanału żeglugowego przez Mierzeję Wiślaną. Dyskusję wyników przeprowadzono na podstawie rezultatów uzyskanych w ramach grantu badawczego rozwojowego realizowanego w latach 2007/2008 przez Instytut Budownictwa Wodnego PAN w Gdańsku we współpracy z Katedrą Budownictwa i Konstrukcji Budowlanych Wydziału Nauk Technicznych Uniwersytetu Warmińsko-Mazurskiego w Olsztynie. Przedstawiono analizę dotyczącą oddziaływania projektowanych falochronów osłaniających wejście do przekopu od strony Zatoki Gdańskiej na odmorskie brzegi Mierzei Wiślanej oraz wpływu ich długości na zapiaszczanie toru wodnego. Analizę wykonano na podstawie autorskiej metody uwzględniającej zmienność uziarnienia osadów. Sformułowano zalecenia optymalizacyjne dotyczące długości projektowanych falochronów.

18

Hydro- and lithodynamic aspects of constructing a navigable canal through the Vistula Spit - Part 2

44%

Kaczmarek L. M. , Biegowski J. , Skillandat J. B.

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2010

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tom nr 13

64-79

EN

The paper discusses hydro- and lithodynamic aspects of a planned construction of a navigable canal across the Vistula Spit. The discussion is based on the results obtained under a research and development grant carried out in 2007-2008 by the Institute of Hydroengineering of the Polish Academy of Sciences in Gdańsk in collaboration with the Chair of Civil Engineering and Building Structures, the Faculty of Technical Sciences, at the University of Warmia and Mazury in Olsztyn. The analysis presented in this paper regarding the effect of the length and position of planned breakwaters on the silting up of the fairway broadens the results of the research perfomed under the above grant by including such aspects as the position of the fairway's axis towards the shore. All analyses were performed employing an innovative method which takes into account the changeable grain size structure of deposists (cf. Kaczmarek L.M., Sawczyński Sz. 2007 and Kaczmarek L.M. 2008). The recommendations regarding an optimum length of planned breakwaters and depth of an approach fairway, presented previously, have found further confirmation.

PL

W artykule przedstawiono aspekty hydro- i litodynamiczne planowanej budowy kanału żeglugowego przez Mierzeję Wiślaną. Dyskusję wyników przeprowadzono na podstawie rezultatów uzyskanych w ramach grantu badawczego rozwojowego realizowanego w latach 2007-2008 przez Instytut Budownictwa Wodnego PAN w Gdańsku we współpracy z Katedrą Budownictwa i Konstrukcji Budowlanych Wydziału Nauk Technicznych Uniwersytetu Warmińsko-Mazurskiego w Olsztynie. Przedstawiona analiza, dotycząca wpływu długości oraz ustawienia projektowanych falochronów na zapiaszczanie toru wodnego, stanowi istotne rozszerzenie wyników badań uzyskanych w ramach grantu o aspekty związane z ustawieniem osi toru względem brzegu. Analizy wykonano, korzystając z nowatorskiej metody uwzględniającej zmienność uziarnienia osadów (por. Kaczmarek, Sawczyński 2007 i Kaczmarek 2008). Potwierdzono zalecenia optymalizacyjne dotyczące długości projektowanych falochronów i głębokości toru podejściowego.