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3352. Experiment v publikačnej praxi mladých právnych vedcov na Slovensku /
- Creator:
- Puchovský, Ján,
- Type:
- text and články
- Subject:
- Právo, časopisy vědecké, fakulty právnické, věda právní, právníci, doktorandi, činnost publikační, and zahraniční periodika a sborníky
- Language:
- Slovak
- Rights:
- unknown
3353. Experimental evaluation of the drag force and drag torque acting on a rotating spherical particle moving in fluid
- Creator:
- Lukerchenko, Nikolay, Kvurt, Yuri, Kharlamov, Alexander, Chára, Zdeněk, and Vlasák, Pavel
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- drag force, drag torque, spherical particle, rotational movement, translational movement, odporová síla, odporový moment, kulovitá částice, rotační pohyb, and translační pohyb
- Language:
- Slovak
- Description:
- The paper describes results of experiments with rotating spherical particles moving in water. Rubber spherical balls with the density close to that of water were speeded up in a special inclined chute that ensured the required particle rotational and translational velocity in the given plane. A standard video system was used to capture particle trajectory and the evaluation was focused on the effects of two dimensionless parameters of the particle motion, Reynolds number and rotational Reynolds number. The values of the drag force and drag torque coefficients were determined from the experimental data and compared with the results of the numerical simulation of the particle motion. Relationships describing the above mentioned quantities, taking into account the mutual influence of the translational and the rotational particle movements and convenient for numerical models were found. and V příspěvku jsou prezentovány výsledky experimentálního výzkumu pohybu rotující kulovité částice ve vodě. Kulovitá částice vyrobená z gumy o hustotě blízké hustotě vody byla uvedena do pohybu v šikmé štěrbině, kde získala rotační i translační rychlost v osové rovině štěrbiny. Trajektorie částic ve vodě byly snímány standardní video kamerou a byl vyhodnocen vliv dvou bezrozměrných parametrů (Reynoldsova čísla a rotačního Reynoldsova čísla) na pohyb částice. Z experimentálních údajů byly určeny hodnoty odporového koeficientu a odporového momentu částice a tyto hodnoty byly porovnány s výsledky numerické simulace pohybu částice. Byly vyhodnoceny vztahy vhodné pro využití při numerickém modelování a popisující vzájemné závislosti výše uvedených veličin a vzájemný vliv translačního a rotačního pohybu částice.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
3354. 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
3355. Experimental investigation of fine-grained settling slurry flow behaviour in inclined pipe sections
- Creator:
- Vlasák , Pavel, Chára , Zdeněk, Matoušek , Václav, Konfršt , Jiří, and Keselý , Mikoláš
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- settling slurry, effect of pipe inclination, concentration distribution, pressure drops, deposition limit, and gamma-ray radiometry
- Language:
- Slovak
- Description:
- For the safe and economical design and operation of freight pipelines it is necessary to know slurry flow behaviour in inclined pipe sections, which often form significant part of pipelines transporting solids. Fine-grained settling slurry was investigated on an experimental pipe loop of inner diameter D = 100 mm with the horizontal and inclined pipe sections for pipe slopes ranging from –45° to +45°. The slurry consisted of water and glass beads with a narrow particle size distribution and mean diameter d50 = 180 μm. The effect of pipe inclination, mean transport volumetric concentration, and slurry velocity on flow behaviour, pressure drops, deposition limit velocity, and concentration distribution was studied. The study revealed a stratified flow pattern of the studied slurry in inclined pipe sections. Frictional pressure drops in the ascending pipe were higher than that in the descending pipe, the difference decreased with increasing velocity and inclination. For inclination less than about 25° the effect of pipe inclinations on deposition limit velocity and local concentration distribution was not significant. For descending pipe section with inclinations over –25° no bed deposit was observed.
- Rights:
- http://creativecommons.org/publicdomain/mark/1.0/ and policy:public
3356. Experimental investigation of hydrophobic bentonite effects on reducing evaporation from water surfaces
- Creator:
- Jajin, Roza Ghahramani, Feizi, Atabak, and Ghorbanpour, Mohammad
- Format:
- počítač and online zdroj
- Type:
- model:article and TEXT
- Subject:
- water evaporation, water surface, hydrophobic bentonite, and hexadecanol monolayer
- Language:
- Slovak
- Description:
- In recent years, due to the occurrence of water shortage and drought problems, particularly in arid and semiarid regions of the world, new methods to reduce evaporation from the surface of dam reservoirs, lakes, and other waterfree surfaces are investigated. This study aimed to use hydrophobic bentonite to reduce water evaporation from water surfaces, on a laboratory scale, and field conditions for the first time. Bentonite initially became hydrophobic by stearic acid (SA). Under such conditions, hydrophobic bentonite floats on the surface of water and forms a thin coating layer. The produced hydrophobic bentonite had a contact angle of 150°, indicating its superhydrophobicity. Evaporation reduction was measured under laboratory and field conditions and it was compared to hexadecanol as the reference material. The results demonstrated that the hydrophobic bentonite efficiency under laboratory conditions was similar to that of hexadecanol and prevented water evaporation by 36%. However, under field conditions, hydrophobic bentonite and hexadecanol efficiencies were 40% and 23% to reduce evaporation for 30 days, respectively. In terms of stability, hexadecanol needed to be re-injected after three days, while hydrophobic bentonite was stable and remained on the surface for more than 100 days under laboratory conditions and for more than 15 days under field conditions without needing reinjection. This coverage with method can be used to reduce evaporation from lakes, tanks, and reservoirs of small dams.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
3357. 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
3358. Experimental investigation of the effect of vegetation on dam break flood waves
- Creator:
- Oguzhan, Semire and Aksoy, Aysegul Ozgenc
- Format:
- počítač and online zdroj
- Type:
- model:article and TEXT
- Subject:
- dam break, flood wave, physical model, Urkmez dam, and vegetation effect
- Language:
- Slovak
- Description:
- Dams have an important role in the industrial development of countries. Irrespective of the reason for dam break, the flood can cause devastating disasters with loss of life and property especially in densely populated areas. In this study, the effects of the vegetation on the flood wave propagation in case of dam break were investigated experimentally by using the distorted physical model of Ürkmez Dam. The horizontal and vertical scales of the distorted physical model are 1/150 and 1/30, respectively. The dam break scenarios were achieved by means of a gate of rectangular and triangular shape. The results obtained from experiments performed with vegetation were compared and interpreted with those obtained from experiments at which the vegetation configuration was absent. The analysis of the experimental data showed that the presence of vegetation causes a significant decrease in water depths as the flood wave propagates to the downstream and greatly reduces its impact on the settlements. It is also revealed that dam break shape plays an important role in temporal variation of flood wave.
- Rights:
- http://creativecommons.org/publicdomain/mark/1.0/ and policy:public
3359. Experimental measurements for improved understanding and simulation of snowmelt events in the Western Tatra Mountains
- Creator:
- Krajčí, Pavel, Danko, Michal, Hlavčo, Jozef, Kostka, Zdeněk, and Holko, Ladislav
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- snow accumulation and melt, snowmelt rate, snowmelt duration, mountains; snow lysimeter, and MIKE-SHE
- Language:
- Slovak
- Description:
- Snow accumulation and melt are highly variable. Therefore, correct modeling of spatial variability of the snowmelt, timing and magnitude of catchment runoff still represents a challenge in mountain catchments for flood forecasting. The article presents the setup and results of detailed field measurements of snow related characteristics in a mountain microcatchment (area 59 000 m2 , mean altitude 1509 m a. s. l.) in the Western Tatra Mountains, Slovakia obtained in winter 2015. Snow water equivalent (SWE) measurements at 27 points documented a very large spatial variability through the entire winter. For instance, range of the SWE values exceeded 500 mm at the end of the accumulation period (March 2015). Simple snow lysimeters indicated that variability of snowmelt and discharge measured at the catchment outlet corresponded well with the rise of air temperature above 0°C. Temperature measurements at soil surface were used to identify the snow cover duration at particular points. Snow melt duration was related to spatial distribution of snow cover and spatial patterns of snow radiation. Obtained data together with standard climatic data (precipitation and air temperature) were used to calibrate and validate the spatially distributed hydrological model MIKE-SHE. The spatial redistribution of input precipitation seems to be important for modeling even on such a small scale. Acceptable simulation of snow water equivalents and snow duration does not guarantee correct simulation of peakflow at shorttime (hourly) scale required for example in flood forecasting. Temporal variability of the stream discharge during the snowmelt period was simulated correctly, but the simulated discharge was overestimated.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
3360. Experimental study on the rheological behaviour of coal ash slurries
- Creator:
- Assefa, K.M. and Kaushal, D.R.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- coal ash slurry, Newtonian fluid, yield stress, plastic viscosity, and relative viscosity
- Language:
- Slovak
- Description:
- Extensive experimental investigations were carried out to evaluate the rheological behaviour of fly ash (FA) slurry without and with the addition of bottom ash (BA) and BA slurry without and with the addition of FA. The FA slurries exhibited Bingham behaviour at solid mass concentrations ranging from 60-65% and mixing proportions from 10- 40%. A substantial reduction in yield stress was observed except for mixing proportion of 40% on which the yield stress and viscosity were increased drastically for all solid concentrations. Hence, it can be concluded that the yield stress and viscosity of FA slurry were very much influenced by adding BA up to the mixing proportion of 30%. The rheological behaviour of BA slurries with and without the addition of FA in proportions of 10-50% was investigated and exhibited Newtonian behaviours for solid mass concentrations ranging from 30-50% without and with the addition of FA. The viscosity increases with increasing the solid concentrations and proportion of FA. Based on these experimental data, a correlation was developed to predict the relative viscosity of BA slurries as a function of solid volume fraction and FA mass proportion of 0-50% and the RMSE and R2 values showed good agreement between the experimental and the predicted data.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public