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  • Author or Editor: Peter Dušička x
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Abstract

This paper presents a proprietary open source code for analysis of granulometric properties of bed load material based on non-intrusive automated image analysis. Vertical bed-surface images are processed using the proposed tool and verified with results obtained by well tested optical granulometry tool Basegrain. The practical application of the proposed tool yields accuracy comparable that of the tested framework and traditional sampling methods. Additionally, results showed that the average D50 grain-size sampled from riverbed of studied river section of river Danube agrees up to 95% with the average D50 sampled from riverbanks.

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The aim of the study is to assess hydro-morphologic evolution of currently cut off meander for 3 river restoration scenarios during 10 days of bank-full discharge. To simulate hydro-morpho-dynamics, a numerical model with movable bed, R2DM is used. Results for scenario with partially opened meander indicate aggradation at inlet of meander and 10% decrease in flow rate. Scenario with fully opened meander shows aggradation at the inlet and 55% decrease in flow rate. Full diversion scenario results in formation of natural river landforms (point bars, cut banks, pools, riffles) and stabilization of river bed evolution.

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Abstract

Recently, the construction of shaft intake structures in Slovakia has increased. The shaft intake structures overcome significant vertical depth over short horizontal distance. The flow of water in these shaft intake structures is therefore very complicated. The velocity field at a shaft intake of a small hydropower plant was investigated on a physical model in a hydraulic laboratory using the particle image velocimetry method. The particle image velocimetry measurements were realized for different shaft depths and the results of this study can increase negative effects of not suitable the design of construction on the flow homogeneity in the turbine intake.

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Abstract

The structural parts of intake structures directly affect the flow velocity distribution in the turbine intake of small hydropower plants, where inhomogeneous flow leads to uneven load of the turbine units causing operational problems. A 2D numerical flow modeling was used for investigations of the flow in an intake structure of a low-head small hydropower plant. The effects of shape changes of the intake structure on the flow velocity distribution in the turbine intakes were investigated and assessed proving significant effect of the shapes of the intake structure on the flow homogeneity in turbine intakes.

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Abstract

One of the main problems at the Hričov weir is the scour development in the riverbed just downstream. It is caused of construction the size of the stilling basin was significantly shortened. Flow energy is dissipating just partially. Each flood makes scour close to the foundations of the structure, which potentially endangers its stability. A permanent solution was experimentally investigated in the hydraulic laboratory at the 2D model in a scale of 1:40. Different variants of the secondary stilling basins were designed to minimize creating scours. The investigation and its results are described in this paper.

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Pollack Periodica
Authors:
Daniel Buček
,
Martin Orfánus
,
Peter Dušička
, and
Peter Šulek

Abstract

Variable renewable energy sources, e.g. solar and wind power, require flexible management of energy sources to stabilize the power grid. Immediate changes in power generation and power usage is compensated for by the operation of hydropower plants. This subsequently leads to frequent flow fluctuations – hydropeaking downstream of the hydropower plant. This study examines the short-term impacts of hydropeaking of hydropower plants on the sediment transport using numerical morphodynamic model. The model is calibrated to field measurements and subjected to various hydropeaking scenarios on daily to sub-daily scale. Based on this study, the effect of hydropeaking of hydropower plant 23.42 km upstream of the studied river section would have negligible effect on the bedload transport in the studied cross section.

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Abstract

Scours creation in riverbed at the Hričov weir is a permanent problem since its construction. It is caused by the shortened stilling basin of the weir. In almost all cases of flow control at the weir the energy is not dissipated sufficiently. A 3D physical model was built in the hydraulic laboratory to investigate the measures for reduction of the scour creation. To simulate uneven loads on the downstream riverbed, a flood discharge controlled by the weir in symmetric and asymmetric operations was used for simulations. The scours were evaluated using short-range photogrammetry for contactless measurements. Based on this method digital models of the riverbed for each simulation were created and the scours were assessed to determine the effect of the investigated measures on scour reduction.

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