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Stationary- and sliding beds in pipe flows of settling slurry
Matoušek, Václav; Krupička, Jan; Chára, Zdeněk
2014 - anglický
Investigations are discussed on the effect of stationary- and sliding beds on a behavior of settling slurry flows. Results are presented of our recent experiments with two fractions of ballotini in a 100-mm-pipe loop. Experimental work contained measurements of concentration profiles and velocity profiles. The experimental results for flows with stationary deposits are compared with predictions using our formulae for solids transport and bed friction in layered flows. CFD simulations are included to validate the velocityprofile measurements and to verify the bed roughness predictions in the flows with stationary beds. Furthermore, the measured velocity profiles are compared to profiles predicted using the log law of the wall with boundary shear velocities determined from the linear distribution of shear stress across the pipe flow. The approach is successful in the flow below the upper wall of the pipe but fails above the top of the deposit where the stress distribution is different as verified by the CFD simulation. The concept of the linear-distribution of shear stress is well applicable in flows with sliding beds. An example is given of a solution for a partially-stratified flow with sliding bed using the 1-D Stress- Distribution based Model.
Klíčová slova:
experiment; hydraulic transport; concentration profile; velocity profile; sheet flow
Plné texty jsou dostupné na vyžádání prostřednictvím repozitáře Akademie věd.
Stationary- and sliding beds in pipe flows of settling slurry
Investigations are discussed on the effect of stationary- and sliding beds on a behavior of settling slurry flows. Results are presented of our recent experiments with two fractions of ballotini in a ...
Jedno-kamerové měření 3D pohybu částic
Chára, Zdeněk; Kysela, Bohuš
2013 - český
V příspěvku je analyzována možnost měření 3D pohybu kulovitých částic pomocí jedné kamery a světelného nože. Zatímco pro určení 2D rychlostního pole částic byla použita standardní sledovací technika (Particle-Tracking-Velocimetry), pro měření třetí složky rychlosti kolmé na rovinu objektivu kamery byla použita jednoduchá metoda založená na měření intenzity světla dopadajícího na pohybující se částici. Article is focused on analysis of measuring 3D particle motion with one camera and light knife. The 3D spherical particle movement is measured using standard particle tracking method (two velocity components) combined with simple method based on light intensity of scattered light by the moving spherical particle.
Klíčová slova:
3D particles; particle motion; measurements
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Jedno-kamerové měření 3D pohybu částic
V příspěvku je analyzována možnost měření 3D pohybu kulovitých částic pomocí jedné kamery a světelného nože. Zatímco pro určení 2D rychlostního pole částic byla použita standardní sledovací technika ...
Long-term hydroecological monitoring in the Krkonoše Mts
Tesař, Miroslav; Šír, Miloslav
2013 - anglický
The cloud and fog water deposition proved to be important delivery mechanism for both water and pollutants in mountainous headwater regions. A fogwater study has been conducted in the Krkonoše Mts. since 1999 till the present time. The sampling site for the observation and evaluation occult precipitation in the Western region was established in the Modrý potok basin (1010–1554 m a.s.l., 2.62 km2) at the highest point of the watershed (passive cloud and fog water collector) while the bulk precipitation and throughfall samplers were installed near to the closure profile of the basin. Rain gauges are evenly situated at six altitudes of the watershed (from 1020 to 1365 m a. s. l.). In the Eastern region the both passive and active collectors were installed close to the Labská bouda chalet (1325 m a.s.l). The active collector (Eigenbrodt, Germany) is operated automatically by the PWD-11 sensor (Vaisala, Finland). Collected samples were stored in polyethylene bottles and transported as soon as possible to the laboratories of the Czech Geological Survey and Geological Institute of ASCR to the chemical analyses. The results for 1999–2011 will be presented in this article. A wide range of concentrations were encountered, most typically exceeding concentrations occurring in rain (so-called enrichment factors were evaluated) and the estimated wet deposition of the most important chemical compounds were calculated and compared with respect to weighted means of bulk precipitation collected in the open area. Based on the model predictions and on the water balance of the forest canopy the annual occult precipitation total for the Krkonoše Mts. was estimated by 20–25 % of the annual falling precipitation total. The research is supported by the Czech Science Foundation (205/09/1918).
Klíčová slova:
occult precipitation; cloud and fog water deposition; water chemistry
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Long-term hydroecological monitoring in the Krkonoše Mts
The cloud and fog water deposition proved to be important delivery mechanism for both water and pollutants in mountainous headwater regions. A fogwater study has been conducted in the Krkonoše Mts. ...
Vyhodnocení disipace turbulentní kinetické energie z gradientů rychlostí měřených v míchané nádobě
Kysela, Bohuš; Konfršt, Jiří; Chára, Zdeněk; Kotek, M.
2013 - český
Disipace turbulentní kinetické energie v míchaných nádobách je důležitým parametrem v procesu míchání. A dle posledních poznatků je také ve většině případů procesem řídícím. Jelikož metoda přímého měření disipace turbulentní kinetické energie a její distribuce v míchané nádobě není dostupná, používají se různé postupy pro její výpočet na základě teorií o turbulenci. Pro míchané nádoby se v praxi využívá hlavně střední hodnota vypočtená z poměru příkonu na hřídeli míchadla vztaženého k celkovému objemu nádoby. Dissipation of the turbulent kinetic energy in mixing vessels is important parameter in mixing process. According to the latest findings it is also in the most cases the control process. This study shows a limits of dissipation rate evaluation using the velocity field obtained from the PIV (Particle Image Velocimetry) results.
Klíčová slova:
kinetic energy; gradients; LDA measuring; TR PIV measuring; Time Resolved Particle Image Velocimetry
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Vyhodnocení disipace turbulentní kinetické energie z gradientů rychlostí měřených v míchané nádobě
Disipace turbulentní kinetické energie v míchaných nádobách je důležitým parametrem v procesu míchání. A dle posledních poznatků je také ve většině případů procesem řídícím. Jelikož metoda přímého ...
Postup seřízení argonového laseru a vláknového zavaděče
Konfršt, Jiří; Kysela, Bohuš; Chára, Zdeněk
2013 - český
Použití laserů v měřících systémech využívajících zařízení LDA (Laser Doppler Anemometry)/PDA (Phase Doppler Anemometry) předpokládá dobrou znalost fyzikálních charakteristik používaného světelného zdroje. Tento příspěvek se zabývá experimentální analýzou parametrů jednotlivě separovaných světelných vlnových délek u Ar-Ion plazmové trubice, pracující v multi-vlnném „ML“ režimu. Motivací práce byla snaha o co nejkvalitnější zavedení světla do světelných vláken a minimalizace ztrát světelného výkonu pro účel dvou-, příp. tří-složkového měření proudového pole v míchané nádobě. Vyšetřovány byly parametry jednotlivých vlnových délek, a to světelný výkon, průběh emise a interference ve vztahu k nastavení apertury laseru a ve vazbě na nastavení proudového / světelného výkonu laseru. V dalším kroku bylo provedeno zavedení světelného záření z laseru pracujícího v „ML“ režimu do transmitteru a dále pomocí optických zavaděčů do mono-modových optických vláken. Do optických vláken byly zavedeny dvě nejsilnější vlnové délky, zelená - 514,5 nm a modrá - 488 nm. Pro současné zavedení oboru barev bylo nutné provést úpravu optické trasy v transmitteru přizvednutím středového hranolového páru u modré barvy. Use of lasers in the measuring systems, which use LDA/PDA devices, expects good knowledge of physical characteristics of used light source namely for multicomponent measurements. This article is focused on the experimental parameter analysis of individually separated light wavelength from Ar-Ion plasma tube, working in multiline “ML” mode. The best laser source parameters: aperture size, power input and quality of the utilized separate wavelengths were obtained and beams were adjusted to the optical fibres.
Klíčová slova:
Ar-Ion laser; Laser Doppler Anemometry (LDA); Phase Doppler Anemometry (PDA)
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Postup seřízení argonového laseru a vláknového zavaděče
Použití laserů v měřících systémech využívajících zařízení LDA (Laser Doppler Anemometry)/PDA (Phase Doppler Anemometry) předpokládá dobrou znalost fyzikálních charakteristik používaného světelného ...
Spinnability of PEO solutions with respect to their aging
Zelenková, Jana; Peer, Petra; Filip, Petr
2013 - anglický
Non - negligible portion of pol ymer commodity suffers from ageing that participates in sometimes significant changes of products attributes. Rheology represents a useful tool for a description of this process. The aim of this contribution is to evaluate possible ageing of PEO solution ( polyethylen e oxide ( M w =300,000 g/mol) dissolved in water at 10 wt.% concentration) based both on rheological characterization and on quality of electrospun fibres. Rheological measurements in steady shear and oscillatory modes were carried out using a rota tional rheometer MCR 501 (Anton Paar, Austria) equipped with the concentric cylinders geometry. The electrospinning measurements were executed with the help of a proposed laboratory device. The tip - to - collector distance attained 20 cm, applied voltage rang ed from 20 to 30 kV. The obtained electrospun fibres were analysed using a scanning electron microscope (VEGA 3, Tescan, Czech Republic). Both types of measurements were carried out in the period of several months during which the solution studied was plac ed in a dark and tempered box (25°C). The measurements indicate no ageing impact on rheological characteristics or quality of electrospun fibres. This guarantees more or less the identical quality of non - woven textiles prepared from PEO solutions regardles s of time period during which the solutions are deposited.
Klíčová slova:
polyethylene oxide (PEO); ageing; electrospinning; rheological properties
Dokument je dostupný na externích webových stránkách.
Spinnability of PEO solutions with respect to their aging
Non - negligible portion of pol ymer commodity suffers from ageing that participates in sometimes significant changes of products attributes. Rheology represents a useful tool for a description of ...
Coarse-grained particles conveying along a pipe bed
Vlasák, Pavel; Chára, Zdeněk; Konfršt, Jiří; Kysela, Bohuš
2013 - anglický
The paper describes the results of a flow visualisation of model coarse-grained fully stratified particle-water mixtures. Investigation was focussed on study of the particle behaviour and carrier liquid and conveyed particles local velocities. Glass balls and washed graded pebble gravel of mean diameter of 6 mm were conveyed by water in a horizontal smooth pipe loop with a transparent pipe viewing section of inner diameter 40 mm. Particle movement along the pipe invert and particulate stationary bed, created by two layers of spherical particles of the same size as the conveyed particles, was studied. The effect of stationary bed on local velocity values of the carrier liquid and conveyed particles were determined. It was conducted that the maximum liquid velocity is significantly shifted from pipe centre to a higher position in the flow pattern with stationary bed.
Klíčová slova:
coarse-grained slurry; flow structure; visualisation; liquid local velocity; particle velocity; rychlost; částice
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Coarse-grained particles conveying along a pipe bed
The paper describes the results of a flow visualisation of model coarse-grained fully stratified particle-water mixtures. Investigation was focussed on study of the particle behaviour and carrier ...
Early warning system for flash floods in the Krkonoše Mts
Tesař, Miroslav; Šír, Miloslav
2013 - anglický
The present contribution describes a sophisticated local warning system (LWS) for detection of local flash floods that is built in the Krkonoše Mts. in the upper of the Úpa river with the closing profile at Horní Maršov (573–1602 m a.s.l., 81.70 km2). This system is based on the new knowledge of the discontinuous character of water transport in an unsaturated zone and involves: (i) instrumentation: (1) stream gauge monitoring stations with data transfer to the internet, (2) monitoring stations (equipped by rain gauge, air and soil thermometers, soil water tensiometers and soil moisture meters) with data transfer to the internet, (ii) software: (1) the internal software of the stream gauge and monitoring stations for the measurement, storage and transfer the data to the dispatching centre, (2) software of a central data repository, (3) software for data transmission in the internet browser, (3) software for the forecasting of flood risk and sending flood alert, (iii) dispatching centre: (1) operating of the data repository, (2) forecasting of the water level for the each of connected stream gauge station, (3) sending flood alert, (iv) handbooks and user’s Guides: (1) hydrological and soil surveying, (2) LWS design, (3) operation and maintenance of the LWS, (v) complete projection documentation of the LWS, (vi) installation of the LWS in a catchment, (vii) testing and routine operation of the LWS. The described LWS is supported by the Technology Agency of the Czech Republic (Project TA02021451).
Klíčová slova:
early warning system; flash flood; surface and soil water monitoring
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Early warning system for flash floods in the Krkonoše Mts
The present contribution describes a sophisticated local warning system (LWS) for detection of local flash floods that is built in the Krkonoše Mts. in the upper of the Úpa river with the closing ...
Improvements of saltation model
Kharlamova, Irina; Vlasák, Pavel
2013 - anglický
The present paper introduces a new model of a bed-load transport. The model simulates a particle motion in the channel with turbulent flow and rough bed. The effects of mutual interaction of conveyed particles with carrier liquid, with bed particles, and also with other conveyed particles are taken into account. The model predicts average saltation characteristics, e.g. saltation length and height, particles distribution in vertical direction, and mass rate of conveyed particles per unit area of channel bed.
Klíčová slova:
částice; modely
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Improvements of saltation model
The present paper introduces a new model of a bed-load transport. The model simulates a particle motion in the channel with turbulent flow and rough bed. The effects of mutual interaction of conveyed ...
Saltation of sand in vicinity of cylindrical column
Kharlamova, Irina; Kharlamov, Alexander; Vlasák, Pavel
2013 - anglický
The paper presents a model of sand sediment transport in water stre am in vicinity of a high cylindrical col umn. It is assumed that an averaged turbulent flow is horizontally layered in vicinity of the cylinder. In ea ch layer the flow around the cylinder is modelled as a potential flow generated by a vertical dipole line. Flow in viscous sub-layer on the surface of the cylinder is neglected. The presented flow model is approximate; however it is simple for use. Trajectories of saltating particles near the cylinder were calculated. Further investigation of such flow will allow a determination of zones where solid particles will collide with the column. That might be useful for prevention of its damage or destruction
Klíčová slova:
saltation of sand; flow around cylinder; logarithmic profile; dipole line; averaged turbulent flow
Plné texty jsou dostupné na vyžádání prostřednictvím repozitáře Akademie věd.
Saltation of sand in vicinity of cylindrical column
The paper presents a model of sand sediment transport in water stre am in vicinity of a high cylindrical col umn. It is assumed that an averaged turbulent flow is horizontally layered in ...
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