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1

Scour around spur dike in curved channel: a review

Tripathi Ravi Prakash, Pandey Kamlesh Kumar

Acta Geophysica

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2022

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Vol. 70, no 5

2469--2485

EN

A spur dike is a hydraulic structure, protruding in a river or channel used for several purposes like protection of river-bank erosion and deepening of the main channel. The present paper discusses pre-existing research work on flow pattern and prediction of temporal and maximum scours depth around the spur dikes placed in different locations at 90◦ and 180° curved channels. The equations having approximately 2.367, 4.47, 0.17, and 0.271 (average) times with their corresponding experimental data. The parameters, influencing the scour process and flow pattern, have been identified as the ratio of flow intensity to critical velocity (V/Vc≥1) is below 1 and special kind of bedding material is approximately 10 % greater than under livebed condition and many more. The numerical value of the Froude number and the geometry of the bed surface material are also discussed in this paper. Based on these parameters, the empirical formulations and experimental studies on local scours around the straight, L-shaped, T-shaped spurs, placed at 30°, 45°, 60°, 120°, and 180° azimuthal angles have been discussed. Various numerical schemes proposed in almost seventy-five literatures have been summarized. A critical review of numerical and experimental results found in different works related to temporal and maximum scour depth, flow characteristics, and bed topography around the dike shows that the data and accompanying results are insufficient for the design of spurs used as river structures in curved channels. There are needs to carry out extensive experiments, under various flow conditions, to examine the flow behavior and scouring processes around the spurs. Due to complex flow pattern and scouring processes, taking place around the spur, it becomes difficult to understand the real physics behind these phenomenon and therefore, data-driven models are suggested to arrive at more reasonable relationships required to be used for design purposes.

2

Effect of seepage on initiation of cohesionless sediment transport

Liu X., Chiew Y.-M.

Acta Geophysica

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2012

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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.

3

O wykorzystaniu wzorów empirycznych do obliczania długości drogi pełnego wymieszania ścieków zrzucanych do rzek i kanałów

Skowysz A.

Przegląd Naukowy Inżynieria i Kształtowanie Środowiska

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2011

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Vol. 20, No. 3

237--246

PL

Większość modeli matematycznych stosowanych do analizy wpływu zrzutu zanieczyszczeń ze ściekami na jakość wód zakłada całkowite wymieszanie w punkcie zrzutu lub w małej odległości od niego. Całkowite wymieszanie jest jednak zjawiskiem rzadkim, a dystans na jakim następuje uwarunkowany jest wieloma czynnikami. Problem wyznaczania odległości na jakiej nastąpi pełne wymieszanie należy rozpatrywać w danym przekroju rzecznym w dwóch wymiarach: poprzecznym i pionowym. Warto zaznaczyć, iż mieszanie uważa się za zakończone wówczas, gdy stopień wymieszania wynosi co najmniej 98%. W artykule przedstawiono wyniki obliczeń odległości pełnego wymieszania zanieczyszczeń w wodzie wyznaczone dla rzeki Wisły poprzez zastosowanie empirycznych metod obliczeniowych spotykanych w literaturze.

EN

Majority of mathematical models, which are used for analysis the contaminant discharge impact on water quality, assume complete mixing in the place of discharge or in the short distance from this point. Nevertheless, the complete mixing phenomenon is very rare and the distance at what it occurs is conditioned by many factors. The problem of estimating the distance at which compete mixing occurs should be considered in a given cross-section of river in two dimensions: horizontal and vertical. It’s worth mentioning that mixing is considered as finished if mixing degree is at least 98 %.This article presents the results of estimations of contaminant complete mixing length in the water of Vistula river which were calculated by using an empirical methods encountered in literature.

4

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

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2011

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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

Shear velocity estimation in hydraulic research

Rowiński P., Aberle J., Mazurczyk A.

Acta Geophysica Polonica

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2005

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Vol. 53, nr 4

567-583

EN

Various methods for determination of shear velocity and bed shear stress in hydraulic research are discussed, comprising gravity method, logarithmic profile method, near-bed Reynolds-stress method, turbulent kinetic energy method, Prandtl based method, Saint Venant method, power law method, pipe flow method, Shields method, and direct methods. These methods are, where applicable, used to estimate shear velocity and/or bed shear stress in different fields of hydraulic research, ranging from flows in compound channels, gravel bed rivers, and cohesive sediment erosion studies to flows under unsteady conditions.

6

Zmiana warunków hydrodynamicznych wzdłuż koryta potoku górskiego w zróżnicowanej zabudową techniczną małej zlewni karpackiej

Radecki-Pawlik A.

Inżynieria Rolnicza

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2004

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R. 8, nr 2

21--33

PL

W pracy przedstawiono, w jaki sposób regulacja potoku górskiego wpływa na zmianę zasadniczych parametrów hydrodynamicznych przepływu, takich jak: prędkość dynamiczna, naprężenia styczne, liczba Froude’a i Reynoldsa, opory ruchu, moc strumienia oraz jednostkowa moc strumienia. Wykazano, że zabudowa bystrotokiem części koryta potoku górskiego znacznie zaburzyła warunki hydrodynamiczne cieku. Badaniami objęty został potok Młynne w Gorcach o częściowo zabudowanym korycie, a częściowo pozostającym w stanie naturalnym.

EN

The paper describes the way in which the river training influences such hydrodynamics stream conditions as shear velocity, shear stresses, stream power, unit stream power, Froude and Reynolds numbers and resistant coefficient. It was shown that after river training the hydrodynamics parameters in the trained part of the stream increased their value. The work is set up in the Młynne stream catchment in Polish Carpathians in Gorce Mountains.

7

Zmiana warunków hydrodynamicznych w rejonie występowania form dennych rzeki nizinnej

Radecki-Pawlik A.

Przegląd Naukowy Inżynieria i Kształtowanie Środowiska

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2003

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Vol. 12, No. 2

82--89

EN

The paper presents an extremely important problem of low land river sand dunes and the influence on the riverbed morphology such hydraulics parameters as velocity of running water, shear velocity, shear stresses and resistant coefficient. The sand dunes are typical features for low land river sand beds. The studies on them undertaken on the Rhine River in Germany (the river reach situated in Niderwalluf) are very important from two points of view : scientific - as dunes are the part of morphology of river bed fluvial system and practice - as dunes very often are the obstacles for river navigation (such a situation had a place on the Rhine). The work was done with thanks to cooperation with scientists from Great Britain (prof. Paul Carling) and Germany (prof. Emil Goelz) who were the heads of the whole project.