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1
Content available remote Numeryczne modelowanie rozmyć poniżej budowli piętrzących
100%
Siwicki P.
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2008
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tom Vol. 17, No. 2
155--168
EN
The scour below the dam is numerically simulated using an Eulerian two-phase model that implements Euler-Euler coupled governing equation for fluid and solid phase and a modified k-ε turbulence closure for the fluid phase and comparison with laboratory results. The modeling system being a part of CFD software package FLUENT. Both flow-particle and particle-particle interactions are considered in the model. During the simulations, the interface between sand and water is specified using a threshold volume fraction of sand. The predictions of bedform evolution are in good agreement with conducted laboratory measurements.
2
Rozmycie grodzy budowlanej zapory Wióry na Świślinie
100%
Fiedler K.
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tom Nr 1
32-33
EN
The destruction of the earth-fill cofferdam on the Wiory dam building site in July 2001 caused by overflowing has been described. The cofferdam was designed in accordance to the obligatory building rules. Its construction slowed down the velocity of its destruction and thanks to it the effects of the freshet downstream the building site have been diminished.
3
Content available remote A review on hydrodynamics of horseshoe vortex at a vertical cylinder mounted on a fat bed and its implication to scour at a cylinder
84%
Gazi A. H. , Afzal M. S.
Acta Geophysica
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2020
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tom Vol. 68, no. 3
861--875
EN
A comprehensive review of the local scour due to vortical fow around a cylindrical bridge pier under steady current is presented in this paper. The mechanism of the formation of vortices, the size, velocity and strength of horseshoe vortex (HSV), formation of the HSV by the separation of laminar and turbulent boundary layer and the scour around a cylindrical pier due to vortices have been presented. The complexity involved in the scour-related calculations, and the scope for future research are discussed in the last section.
4
Content available remote Experimental study of debris-induced scour around a slotted bridge pier
84%
Hamidifar H. , Nezhadian D. M. A. , Carnacina I.
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tom Vol. 70, no 5
2325--2339
EN
One of the most common problems for river engineers is the accumulation of waterborne debris upstream of the bridge piers. In addition to reducing the cross-sectional flow area, debris increases the drag force exerted to the pier and contributes to scour. Several studies have been carried out by previous researchers to examine the usefulness of different types of countermeasures. The effectiveness of these countermeasures is not well understood when debris accumulation occurs. In this study, the effect of debris accumulation on the efficiency of a bridge pier slot, as scour countermeasure, is investigated experimentally. A total of 54 experiments were carried out under different hydraulic and debris geometrical conditions. The results showed that slots were effective in protecting bridge piers against scouring in presence of debris. Depending on the debris shape, the reduction efficiency may increase or decrease for a slotted pier in presence of debris accumulation when compared to the standard pier conditions without debris accumulation. Except for the inverse pyramid shape, the maximum scour is generally more reduced due to sheltering effect when the debris is located on the bed. While debris accumulation can lead to a reduction of the slot efficiency, the slot can be considered a reliable countermeasure against scouring. The outcome of this study can help the design of new bridges affected by large wood debris accumulations.
5
Content available remote Heterogeneous fog generated with the effect of light scattering and blur
84%
Gawron M. , Boryczka U.
Journal of Applied Computer Science
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2018
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tom Vol. 26, nr 2
31--43
EN
The development of computer graphics forces new requirements on the developers, which will make the virtual world more similar to the real world. One of these elements is the simulation of fog. Common fog algorithms mix the color of the scene with the color of the fog over a certain distance. However, one feature of the naturally foggy scenery is ignored. With the distance and density of the fog, the observed scenery or individual objects become more blurred. In this paper we will present our implementation of the distance fog in the Unreal Engine 4, including the effect of blurring the foggy areas, simulating of light scattering and variations in fog density using noise.
6
Numeryczna analiza wpływu budowy podpory mostu na rzece Wiśle na przepływ i rozmycie dna koryta rzeki
67%
Szydłowski M. , Zima P.
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tom R. 69, nr 10
553--558
PL
Opisano podejście do obliczeń hydraulicznych oparte na analizie dwuwymiarowego ruchu wody. Jako przykład przedstawiono analizę hydrodynamiki przepływu w rejonie budowanego mostu na Wiśle koło Kwidzyna. Na jej podstawie oszacowano intensywność ruchu rumowiska w rejonie podpory mostu. Omówiono także klasyczne podejście do oszacowania lokalnych rozmyć dna koryta.
EN
In this paper the two-dimensional hydrodynamic model was presented and used for the flow simulation. The hydraulic analysis for the bridge on the Vistula river near the Kwidzyn is presented as a case study example. The results were used for the identification of debris transport and river bed deformation process. The paper also presents standard approach to the calculation of local scour.
7
Content available remote Local scour due to water jet from a nozzle with plates
67%
Kartal V. , Emiroglu M. E.
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tom Vol. 69, no. 1
95--112
EN
In this study, local scour occurring downstream from a nozzle with and without plates formed in cohesionless materials was investigated experimentally. The experiments were performed to determine scour geometry, maximum scour depth, and the efect of aeration on scour for water jets impinged obliquely into the downstream pool. Dimensionless variables afecting the scour were determined as densimetric Froude number, dimensionless impingement length, and the ratio of densimetric Froude number to dimensionless impingement length. Experiments were conducted for three nozzle diameters with plates, three nozzle diameters without plates, two diferent impingement lengths, and three diferent exit velocities. The results of the experiments showed that the use of the plates in the nozzle, jet impact velocity, jet shape, jet expansion, jet impingement length, and air entrainment rate were critical parameters for scour geometry. As a result, it was found that the jets from a nozzle with plates entrained more air bubbles into the impingement pool than jets from nozzles without plates, thereby decreasing maximum scour depth by spreading the scour over a larger area. This was evident by increasing the impingement length. In addition, scour equations were obtained to determine maximum scour depth, ridge height, and scour hole length from experimental data.
8
Content available Badania własności wybranych cech dyskryminacyjnych obrazów tekstur
67%
Rudnicki Z.
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tom T. 13, z. 3/1
959-969
PL
Przedstawiono wyniki badań kilkudziesięciu cech stosowanych dla rozróżniania klas badanych obrazów typu teksturowego. Uwzględniono cechy wyznaczane na podstawie takich charakterystyk jak: histogram, macierz gradientu, macierz przejść tonalnych, macierz długości pasm oraz model autoregresji. W szczególności badano wrażliwość poszczególnych cech na zmiany: jasności, kontrastu i rozmycia obrazów oraz uporządkowania struktury. Dokonano selekcji najlepszych cech dyskryminacyjnych.
EN
The paper presents the results of investigation of many image features commonly used in discrimination of texture image classes. The features calculated from: histogram, gradient matrix, co-occurrence matrix, run-length matrix and autoregression model were taken into consideration. The sensivity of these features on the changes of brightness, contrast, blurring and structure arrangement were investigated and the best discriminators were selected.
9
Rozmycia przy przeprawach mostowych
59%
Jarominiak A.
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2020
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tom R. 76, nr 10
481--489
PL
Nawiązując do mostu Południowego przez Wisłę w Warszawie, scharakteryzowano w artykule problemy rozmyć zagrażających bezpieczeństwu mostów.
EN
In reference to the South Bridge across the Vistula river in Warsaw, the article describes the problems of scour that threaten safety of the bridges.
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