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Electrodiffusion Diagnostics of Apparent Wall Slip in Polymer Solutions
Wein, Ondřej ; Tovčigrečko, Valentin ; Večeř, M. ; Sobolík, Václav
Two substantially improved experimental methods, the apparent wall slip (AWS) rotational viscometry with a Morse-taper sensor and electrodiffusion (ED) flow diagnostics with autocalibrated friction probes, are used to study near-to-wall velocity profiles in aqueous solutions of high-molecular polysaccharides under viscometric flow conditions. By comparing the velocity data from the both methods, estimates of the depleted layer thickness in dependence on wall shear stress are obtained. The ED data support the two-layer model of AWS effect, with the constant enhanced fluidity across the depleted layer.
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The Study of Interactions of Bubbles with Solid Surface. The Effect of Surfactant Concentration and Type of Solid Surface
Vobecká, Lucie ; Zedníková, Mária ; Vejražka, Jiří ; Růžička, Marek
This contribution deals with experimental study of interactions between a bubble and a solid horizontal surface. The influence of surfactant concentration in liquid and of material of the solid surface on the interaction is observed. It is observed that the material of solid surface has not significant influence on the hydrodynamics of impact of bubble on a wall. The impact velocity is not affected by surfactant presence because the liquid flow around the bubble moves adsorbed surfactants to rear of the bubble and the interface at top of the bubble stays mobile. The presence of surfactant has strong effect on the bubble rebound, as the rebound velocity and the maximal distance of bubble from the wall decreases with increasing surfactant concentration. No bubble rebound is observed at high concentration of surfactant.
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Asymmetric Hydrogenation Reactions
Klusoň, Petr ; Floriš, T.
In this contribution some information on the research of catalytic properties of homogeneous Ru catalysts are presented. Most attention is paid to the BINAP complexes and their coexistence with ionic liquids as potential reaction media for such hydrogenations.
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Experiments on Large Bubbles Rising in an Inclined Flat Channel
Tihon, Jaroslav ; Pěnkavová, Věra ; Vejražka, Jiří
The motion of single air bubbles in an inclined flat water channel is investigated experimentally. The electrodiffusion technique of near-wall flow diagnostics is applied to measure the wall shear stress distribution under large bubbles rising along the upper channel wall. The directionally sensitive, two-strip electrodiffusion probes are used to detect the location of flow reversal in a thin liquid film separating the moving bubble from the wall. The electrodiffusion measurements are synchronized with the visual observation of bubble movement done by a high-speed camera. The experiments are carried out for three different channel heights (1.5, 4, and 8 mm) and cover a wide range of channel inclination angles (from horizontal to vertical position). The experimental results on bubble motion characteristics obtained in stagnant and co-flowing liquid arrangements are confronted with the recent predictions and scaling provided by theoretical models.
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Volumetric Behaviour of Binary and Ternary Liquid Systems Composed of Toluene, Isooctane and Methyl tert-Butyl Ether at Temperatures from 298.15 K to 328.15 K
Linek, Jan ; Morávková, Lenka ; Wagner, Zdeněk
The densities and speeds of sound of the binary systems toluene plus isooctane, MTBE plus toluene and MTBE plus isooctane and of the ternary system toluene plus isooctane plus MTBE were measured at four temperatures within 298.15 K and 328.15 K, and the respective values of excess volumes EVm and adiabatic compressibility κS were calculated. The EVm and κS values of the binary systems were fitted to the Redlich-Kister equation on applying the weighted gnostic method. The EVm values for the MTBE plus toluene system are negative and decreasing with increasing temperature. The other binary systems show positive EVm with comparatively small temperature dependence. The volumetric data on the binaries and the ternary are of practical importance and besides, serve for testing the correlation procedures for fitting and predicting ternary data from binary ones.
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