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Local velocity scaling in T400 vessel agitated by Rushton turbine in a fully turbulent region
Šulc, R.; Ditl, P.; Fořt, I.; Jašíková, D.; Kotek, M.; Kopecký, V.; Kysela, Bohuš
2017 - English
The hydrodynamics and flow field were measured in an agitated vessel using 2-D Time Resolved Particle Image Velocimetry (2-D TR PIV). The experiments were carried out in a fully baffled cylindrical flat bottom vessel 400 mm in inner diameter agitated by a Rushton turbine 133 mm in diameter. The velocity fields were measured in the zone in upward flow to the impeller for impeller rotation speeds from 300 rpm to 850 rpm and three liquids of different viscosities (i.e. (i) distilled water, ii) a 28% vol. aqueous solution of glycol, and iii) a 43% vol. aqueous solution of glycol), corresponding to the impeller Reynolds number in the range 50 000 < Re < 189 000. This Re range secures the fully-developed turbulent flow of agitated liquid. In accordance with the theory of mixing, the dimensionless mean and fluctuation velocities in the measured directions were found to be constant and independent of the impeller Reynolds number. On the basis of the test results the spatial distributions of dimensionless velocities were calculated. The axial turbulence intensity was found to be in the majority in the range from 0.388 to 0.540, which corresponds to the high level of turbulence intensity.
Keywords:
agitated vessel; Rushton turbine; PIV
Fulltext is available at external website.
Local velocity scaling in T400 vessel agitated by Rushton turbine in a fully turbulent region
The hydrodynamics and flow field were measured in an agitated vessel using 2-D Time Resolved Particle Image Velocimetry (2-D TR PIV). The experiments were carried out in a fully baffled cylindrical ...
Simulation of collagen solution flow in rectangular capillary
Kysela, Bohuš; Skočilas, J.; Zitny, R.; Stancl, J.; Houska, M.; Landfeld, A.
2017 - English
The viscoelastic properties of foods and polymers can be evaluated from flow of the material in capillary with specified dimension and shape. The extrusion rheometer equipped by capillary with rectangular cross-section was used for determination of the rheological behaviour of water collagen solution. The measurements of the axial profiles in longitudinal direction of the total stresses at capillary wall were performed for various shear rates. The linear viscoelastic model of Oldroyd B type: White-Metzner model was used for simulation of fluid flow in OpenFOAM software package. The simulations describe the effect of relaxation time on wall total stress in convergent-divergent capillary.
Keywords:
collagen; viscoelastic model; convergent-divergent capillary
Fulltext is available at external website.
Simulation of collagen solution flow in rectangular capillary
The viscoelastic properties of foods and polymers can be evaluated from flow of the material in capillary with specified dimension and shape. The extrusion rheometer equipped by capillary with ...
Hydrologie malého povodí 2017
Brych, Karel; Tesař, Miroslav
2017 - Czech
CD představuje pné texty vědeckých článků. Články byly připraveny jako příspěvky pro konferenci s mezinárodní účastí “Hydrologie malého povodí 2017”, která se konala 18. až 20.4.2017 v Praze. Konferenci pořádaly: Ústav pro hydrodynamiku AVČR, Ústav hydrológie SAV, Česká vědeckotechnická vodohospodářská společnost, Český hydrometeorologický ústav, Český národní výbor pro hydrologii. Knihu vydal Ústav pro hydrodynamiku AV ČR, v. v. i., v Praze roku 2017. The CD includes the full text of scientific articles. These articles were prepared as the contributions for the Conference with international participation “Hydrology of a small basin 2017” that was held from April 18th to April 20th 2017 in Prague. The Conference was organized by the Institute of Hydrodynamics ASCR in Prague, Institute of Hydrology SAS in Bratislava, the Czech Water Management Society in Prague, Czech Hydrometeorological institute in Prague and Czech Committee for Hydrology. The book was published by the Institute of Hydrodynamics ASCR in Prague in 2017
Keywords:
small basin; experimental hydrology; water balance
Available in digital repository of the ASCR
Hydrologie malého povodí 2017
CD představuje pné texty vědeckých článků. Články byly připraveny jako příspěvky pro konferenci s mezinárodní účastí “Hydrologie malého povodí 2017”, která se konala 18. až 20.4.2017 v Praze. ...
The minimum record time for PIV measurement in a vessel agitated by a Rushton turbine
Šulc, R.; Ditl, P.; Fořt, I.; Jašíková, D.; Kotek, M.; Kopecký, V.; Kysela, Bohuš
2017 - English
In PIV studies published in the literature focusing on the investigation of the flow field in an agitated vessel the record time is ranging from the tenths and the units of seconds. The aim of this work was to determine minimum record time for PIV measurement in a vessel agitated by a Rushton turbine that is necessary to obtain relevant results of velocity field. The velocity fields were measured in a fully baffled cylindrical flat bottom vessel 400 mm in inner diameter agitated by a Rushton turbine 133 mm in diameter using 2-D Time Resolved Particle Image Velocimetry in the impeller Reynolds number range from 50 000 to 189 000. This Re range secures the fully-developed turbulent flow of agitated liquid. Three liquids of different viscosities were used as the agitated liquid. On the basis of the analysis of the radial and axial components of the mean- and fluctuation velocities measured outside the impeller region it was found that dimensionless minimum record time is independent of impeller Reynolds number and is equalled N. t(Rmin) = 103 +/- 19.
Keywords:
agitated vessel; Rushton turbine; PIV; averaging limits
Fulltext is available at external website.
The minimum record time for PIV measurement in a vessel agitated by a Rushton turbine
In PIV studies published in the literature focusing on the investigation of the flow field in an agitated vessel the record time is ranging from the tenths and the units of seconds. The aim of this ...
Sezónní proměnlivost parametrů půdních modelů
Šípek, Václav; Tesař, Miroslav
2016 - Czech
Simulace nasycení půdního profilu v malém horském povodí a testování dvou sezónních setů parametrů. Simulation of saturation of the soil profile in the small mountain river basins and testing of two seasonal sets of parameters.
Keywords:
soil moisture; seasonal variability; saturated hydraulic conductivity; poresize distribution; hydrological modelling; soil hydraulic parameters
Available in digital repository of the ASCR
Sezónní proměnlivost parametrů půdních modelů
Simulace nasycení půdního profilu v malém horském povodí a testování dvou sezónních setů parametrů....
Multi-functional composites with integrated nanostructured carbon nanotubes based sensing films
Slobodian, P.; Pertegás, S.L.; Schledjewski, R.; Matyáš, J.; Olejník, R.; Říha, Pavel
2016 - English
Carbon nanotubes are exceptional nano-objects with respect to their remarkable properties, holding great potential in new polymeric materials design with unique characteristics. To illustrate it, the conventional glass reinforced epoxy composite is combined with a layer of entangled network of carbon nanotubes deposited on polyurethane non-woven membrane. The prepared nano-composite is studied for their diverse mjulti-functional applications involving extension and compression strain sensing composite, remoulding by means of resistance Joule heating and radiating as a planar micro strip antenna operating at frequencies of 2MHz up to 4GHz.
Keywords:
epoxy composite; glass fibers; carbon nanotubes; electro-mechanical properties
Fulltext is available at external website.
Multi-functional composites with integrated nanostructured carbon nanotubes based sensing films
Carbon nanotubes are exceptional nano-objects with respect to their remarkable properties, holding great potential in new polymeric materials design with unique characteristics. To illustrate it, the ...
Systém včasného varování před přívalovými povodněmi s uvažováním stavu vody v půdě – příklad pro horní Úpu
Tesař, Miroslav
2015 - Czech
Contribution describes an early warning system for flash flood detection that has been built in the Giant Mts. This system is located in the upper part of the Úpa River basin and Lysečinský Brook basin. The closing profiles of these basins are situated in Horní Maršov (81,7 km2 and 18,3 km2). Forecasting of flood risk is based on model approach, which uses measured hydrological and hydrometeorological quantities (rain intensity and total, discharge, soil moisture, tensiometric pressure of the soil water, air and soil temperature) as input data. Contribution describes an early warning system for flash flood detection that has been built in the Giant Mts. This system is located in the upper part of the Úpa River basin and Lysečinský Brook basin. The closing profiles of these basins are situated in Horní Maršov (81,7 km2 and 18,3 km2). Forecasting of flood risk is based on model approach, which uses measured hydrological and hydrometeorological quantities (rain intensity and total, discharge, soil moisture, tensiometric pressure of the soil water, air and soil temperature) as input data.
Keywords:
early warning system; flash flood; surface and soil water monitoring
Available in digital repository of the ASCR
Systém včasného varování před přívalovými povodněmi s uvažováním stavu vody v půdě – příklad pro horní Úpu
Contribution describes an early warning system for flash flood detection that has been built in the Giant Mts. This system is located in the upper part of the Úpa River basin and Lysečinský Brook ...
Hydrologie malého povodí 2014
Brych, Karel; Tesař, Miroslav
2014 - Czech
Kniha představuje pné texty vědeckých článků. Články byly připraveny jako příspěvky pro konferenci s mezinárodní účastí "Hydrologie malého povodí 2014", která se konala 22. až 24.4.2014 v Praze. Konferenci pořádaly: Ústav pro hydrodynamiku AVČR, Praha; Ústav hydrológie SAV, Bratislava; Česká vědeckotechnická vodohospodářská společnost, Praha; Český hydrometeorologický ústav, Praha; Český národní výbor pro hydrologii. Knihu vydal Ústav pro hydrodynamiku AV ČR, v. v. i., v Praze roku 2014. The book includes the full text of scientific articles. These articles were prepared as the contributions for the Conference with international participation “Hydrology of a small basin 2014” that was held from April 22nd to April 24th 2014 in Prague. The Conference was organized by the Institute of Hydrodynamics ASCR in Prague, Institute of Hydrology SAS in Bratislava, the Czech Water Management Society in Prague, Czech Hydrometeorological institute in Prague and Czech Committee for Hydrology. The book was published by the Institute of Hydrodynamics ASCR in Prague in 2014.
Keywords:
small basin; experimental hydrology; water balance
Available in digital repository of the ASCR
Hydrologie malého povodí 2014
Kniha představuje pné texty vědeckých článků. Články byly připraveny jako příspěvky pro konferenci s mezinárodní účastí "Hydrologie malého povodí 2014", která se konala 22. až 24.4.2014 v Praze. ...
Spinnability of PEO solutions with respect to their aging
Zelenková, Jana; Peer, Petra; Filip, Petr
2013 - English
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.
Keywords:
polyethylene oxide (PEO); ageing; electrospinning; rheological properties
Fulltext is available at external website.
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 ...
Statistická transformace srážkových dat z regionálního klimatického modelu na specifické podmínky povodí Malše
Hnilica, Jan; Šípek, Václav
2011 - Czech
Příspěvek popisuje proces adaptace srážkových dat z regionálního klimatického modelu, založený na transformaci distribučních funkcí pozorovaných a modelových hodnot. Navrhli a otestovali jsme dva postupy vedoucí k posunu statistických parametrů modelových dat směrem k realističtějším hodnotám. Testováním na datech z meteorologických stanic na povodí Malše jsme ověřili dobrou použitelnost uvedených metod. Paper describes procedure of statistical adaptation of the raw large-scale climate model data based on transformation between cumulative distribution functions of the model and real datasets. We developed two alternative ways and we validated those using data from Malse river basin.
Keywords:
statistical downscaling; REMO model; gamma distribution
Available in digital repository of the ASCR
Statistická transformace srážkových dat z regionálního klimatického modelu na specifické podmínky povodí Malše
Příspěvek popisuje proces adaptace srážkových dat z regionálního klimatického modelu, založený na transformaci distribučních funkcí pozorovaných a modelových hodnot. Navrhli a otestovali jsme dva ...
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