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Start Over Creator Krupička, Jan

2. Experimental investigation of coarse particles-water mixture flow in horizontal and inclined pipes

Creator:
Vlasák, Pavel, Chára, Zdeněk, Krupička, Jan, and Konfršt, Jiří
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
hydraulic pipelining, coarse-grained slurry, pressure drops, pipe inclination, and concentration distribution
Language:
Slovak
Description:
The effect of solid concentration and mixture velocity on the flow behaviour, pressure drops, and concentration distribution of coarse particle-water mixtures in horizontal, vertical, and inclined smooth stainless steel pipes of inner diameter D = 100 mm was experimentally investigated. Graded basalt pebbles were used as solid particles. The study revealed that the coarse-grained particle-water mixtures in the horizontal and inclined pipes were significantly stratified. The solid particles moved principally in a layer close to the pipe invert; however for higher and moderate flow velocities, particle saltation became the dominant mode of particle conveyance. Frictional pressure drops in the horizontal pipe were found to be markedly higher than in the vertical pipe, while the frictional pressure drops in the ascending pipe increased with inclination angle up to about 30°.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

3. Experimental investigation of internal structure of open-channel flow with intense transport of sediment

Creator:
Matoušek, Václav, Bareš, Vojtěch, Krupička, Jan, Picek, Tomáš, and Zrostlík, Štěpán
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
acoustic anemometry, plane bed, solid-liquid flow, and tilting flume experiment
Language:
Slovak
Description:
Gravity-driven open-channel flows carrying coarse sediment over an erodible granular deposit are studied. Results of laboratory experiments with artificial sediments in a rectangular tilting flume are described and analyzed. Besides integral quantities such as flow rate of mixture, transport concentration of sediment and hydraulic gradient, the experiments include measurements of the one-dimensional velocity distribution across the flow. A vertical profile of the longitudinal component of local velocity is measured across the vertical axis of symmetry of a flume cross section using three independent measuring methods. Due to strong flow stratification, the velocity profile covers regions of very different local concentrations of sediment from virtually zero concentration to the maximum concentration of bed packing. The layered character of the flow results in a velocity distribution which tends to be different in the transport layer above the bed and in the sediment-free region between the top of the transport layer and the water surface. Velocity profiles and integral flow quantities are analyzed with the aim of evaluating the layered structure of the flow and identifying interfaces in the flow with a developed transport layer above the upper plane bed.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

4. Gamma-ray-based measurement of concentration distribution in pipe flow of settling slurry: vertical profiles and tomographic maps

Creator:
Krupička, Jan and Matoušek, Václav
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
two-phase flow, gamma radiometry, computational tomography, and slurry flow experiment
Language:
Slovak
Description:
Principles of gamma-ray-based measurement are summarized and their application is demonstrated on an operation of the radiometric facility installed in the test loop for slurry flows at the Institute of Hydrodynamics. The facility is able to measure vertical profiles of chord-averaged concentrations and concentration maps in the pipe cross section. A methodology of measurement is proposed including detection and quantification of random and systematic errors. Experimental results are discussed in the light of the proposed methodology. Experimentally determined vertical profiles of concentration are presented for slurry flows of four different fractions of glass beads. The tomographic application of the radiometric device is demonstrated on a measured concentration map and a suitable image reconstruction method is tested. High reliability of measured concentration distributions is proved except for regions near the pipe wall. The radiometric method is shown to be a useful tool for measurement of concentration distribution in slurry flow through a pipe.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

5. Gradually varied transport of bed load in sheet flow: mathematical and physical modeling

Creator:
Zrostlík, Štěpán, Krupička, Jan, Picek, Tomáš, Bareš, Vojtěch, and Matoušek, Václav
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
intense sediment transport, unsteady flow, steady flow, bed roughness, flume experiment, and steep slope
Language:
English
Description:
Intense transport of sediment is studied in flows of steep slopes. Transport- and friction formulae suitable for flows at high shear stress above eroded bed are discussed. The formulae are further incorporated to a proposed simple model for open-channel flow with gradually varied transport of sediment. Two variants of the formulae are used alternatively in the model. Tilting-flume experiments are described that provided steady-flow data suitable for a validation of the formulae and unsteady-sediment-transport data for a validation of the designed model of gradually varied transport. A comparison of experimental results with formulae predictions and model simulations shows a very reasonable agreement for both variants of the transport and friction formulae. and Obsahuje seznam literatury a znaků
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

6. On equivalent roughness of mobile bed at high shear stress

Creator:
Matoušek, Václav and Krupička, Jan
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
bed shear, experiment, hydraulic transport, sediment transport, tření o dno, hydraulická doprava, and pohyb splavenin
Language:
Slovak
Description:
The friction conditions at the top of a mobile bed are discussed for flows in the upper-plane-bed regime, i.e. for the flows with values of the bed Shields parameter larger than approximately 0.6. A special attention is devoted to flows of the bed Shields parameter bigger than 2. Experimental data for flows at high bed shear are collected from literature and new data are added from own measurements of flows of a 1.36-mm sand slurry in the 100-mm pipe loop of the Institute of Hydrodynamics. The database represents flows of very different solids and covers friction conditions within a broad range of Shields parameters up to the maximum value of about 23. The paper analyses the data in order to evaluate a relationship among the equivalent roughness of the top of the bed and other relevant parameters. A semi-empirical formula is proposed that relates the equivalent roughness to the bed Shields parameter, the ratio of flow velocity and particle settling velocity, and the ratio of flow hydraulic radius and particle diameter. The formula is applicable primarily to flows of combined load (contact- and suspended loads together). and Příspěvek se zabývá mechanismem tření na povrchu erodovatelného dna za podmínek horního režimu pohybu splavenin nad plochým dnem, to jest při hodnotách Shieldsova parametru větších než přibližně 0,6. Zvláštní pozornost je věnována proudění při Shieldsově parametru větším než 2. Z literatury byla sebrána experimentální data pro proudění za vysokých smykových napětí, ke kterým byla přidána nová data z vlastních měření s pískem velikosti středního zrna 1,36 mm v potrubí průměru 100 mm trubního okruhu Ústavu pro hydrodynamiku AV ČR. Databáze obsahuje výsledky měření pro částice různých vlastností v širokém rozsahu hodnot Shieldsova parametru až do hodnoty okolo 23. Příspěvek analyzuje data za účelem stanovení závislosti hydraulické drsnosti povrchu sedliny na ostatních parametrech proudění. Je navržen semiempirický vztah, který předpokládá závislost hydraulické drsnosti na Shieldsově parametru, poměru rychlosti proudění k usazovací rychlosti částic a poměru hydraulického poloměru průtočného profilu k velikosti částic. Tento vztah se doporučuje především pro proudění nesoucí jak dnové splaveniny, tak suspendované částice.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

7. Validation of transport and friction formulae for upper plane bed by experiments in rectangular pipe

Creator:
Matoušek, Václav, Krupička, Jan, and Picek, Tomáš
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
sediment transport, sheet flow, bed load, and suspended load
Language:
Slovak
Description:
The paper describes results of validation of authors' recently proposed formulae for sediment transport and bed friction in the upper plane bed regime using laboratory experiments in a pressurized pipe. Flows of mixture of water and fine to medium ballotini (d50 = 0.18 mm) were observed in a rectangular pipe (51 x 51 mm) with a deposit at the bottom of the pipe. A comparison of test results with transport-formula predictions shows a satisfactory match confirming a good prediction ability of the proposed transport formula at high bed shear. A prediction ability of the friction formulae appears to be less convincing but still reasonable. A joint use of the formulae for transport and friction predicts the delivered concentration of transported sediment within the accuracy range of ± 40 per cent for flows in which transported sediments strongly affect the bed friction, i.e. for flows with delivered concentration of sediment higher than say 3 per cent.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public