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Použití metody konečných objemů pro proudění s volnou hladinou
Hoření, Bohumír ; Chára, Zdeněk
The contribution deals with an application of discontinuous Galerkin method to free surface flow calculation. Both the super- and sub-critical flows are studied for steady and unsteady flow conditions. The numerical method is tested experimentally on flow over a broad crest weir of height to length ratio 1/8. Also VOF (volume of fluid) method is tested for the same geometrical configuration.
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Místní tlakové ztráty při proudění vody s přísadou micelárních aditiv
Mík, Václav ; Šesták, J. ; Kořenář, Josef ; Myška, Jiří
We have studied the influence of three cationic surfactants Arquad S50, CTAB and CTAC on three different types of local pressure drops. Experiments were done on a closed hydraulic loop with the range of Reynolds numbers from 1.600 to 23.000. Four different solution concentrations were investigated. Even though all three tested additives show similar drag reduction in the straight tube, there is a substantial difference in effectiveness at local loses.
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Infiltration pattern changes related to the presence of soil
Votrubová, Jana ; Kosugi, K. ; Mizuyama, T.
For a period of three years, soil moisture distribution was monitored within a 50 cm × 50 cm transect on a forested hill-slope (Fudoji experimental watershed, central Japan). The site is covered by the forest brown soil (Cambisol) approx. 1 m deep underlain by weathered granite bedrock. Soil 25 moisture probes (CS615 Water Content Reflectometer, Campbell Scientific, Inc.) arranged in a 5×5 matrix spaced by 10 cm were used. The readings were collected in 5-minute intervals. The aim of the study was to assess temporal stability of the infiltration process under natural conditions.
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Dominant flow features of twin jets in crossflow
Kolář, Václav ; Savory, E.
A survey of the recent studies of "twin jets in crossflow" (TJICF) by the present authors is carried out and extended in terms of results of the velocity-field analysis based on decomposition techniques. Similarities and differences between the dominant mean-flow vortical features, vorticity and circulation associated with three basic ground arrangements (tandem, side-by-side and oblique arrangements) are examined, and the comparison with the single jet case is carried out as well.
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Occult precipitation and chemistry of a small mountainous catchment
Tesař, Miroslav ; Šír, Miloslav ; Fottová, D.
The present contribution deals with the importance of occult precipitation from the wind-driven low clouds and fogs onto the vegetation cover in the selected mountainous regions of the Czech Republic (Šumava Mts., Jizerské hory Mts. and Krkonoše – Giant Mts.). The experimental monitoring network and sample taking devices for the collecting of samples of water from fogs and low clouds are described in fully details. The attention is paid especially to the evaluation of water and pollutants amount incoming to the monitored regions via occult precipitation.
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Plant transpiration and self-organization of hydrologic cycle
Šír, Miloslav ; Lichner, Ľ. ; Tesař, Miroslav
We quantified the influence of plant transpiration on the entropy production associated with the degradation of solar energy on the Earth’s surface covered by plants. Two surfaces were studied: (1) biotic surface – plant transpiration taken as equal to the potential one, (2) abiotic surface – plant transpiration taken as if equal to zero. Two sources of entropy were taken into account – the entropy production associated with the conversion of solar radiation into (1) the sensible heat, and (2) latent heat. Surface processes in hydrologic cycle were examined in the experimental watershed Liz located in the Bohemian Forest (Czech Republic). We found that in the growing season 1992 the entropy production in humid hydrologic cycle (the Earth’s surface is biotic) was considerably higher than in the arid one (in 39 % of days the Earth’s surface behaved as biotic, in 61 % of days behaved as abiotic). Considering that the biotic effect on the Earth’s functioning can be assessed using the entropy production, we can assume that the hypothesis that biota – represented as a biotic surface – regulates Earth’s environment is proved in the watershed scale.
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Sediments rich in Al and Fe formed at groundwater of borewells as a specific part of hydrogeochemical cycle at Podluží
Ďurďová, Libuše
The article summarises results of investigation of the precipitates from sediments and sludge at the bottom of the borewells at the wellfield Podluží and its vicinity. The article presents overview of petrography structure of rocks of boreweles VIS from wellfield Podluží, data on groundwater chemistry change in the Morava river watershed (from wellfield Kněžpole are given Kurlovov patterns of water chemistry from years 1960-1985), tables of water chemistry from VIS borewells from y. 1989 and 2002, composition of sediments from VIS borewells, sediments from the Morava river and canals at wellfield Podluží, composition of gely, X-ray analyses of metal precipitates with elemental Al, Si and Fe.
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Measurement of the velocity field in a ribbed channel
Chára, Zdeněk
The contribution deals with an experimental investigation of the turbulent along a ribbed channel bottom. The main goal is an application of ultrasound velocity profile technique for measurement of the turbulent flow characteristics in complex geometries. Four configurations of the ribbed surfaces were tested with fixed ribs of square cross section and variable groove widths. The experiments were performed in a water channel.
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