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Povaha toku modelových suspenzí
Kulaviak, Lukáš ; Večeř, Marek ; Růžička, Marek ; Drahoš, Jiří ; Hladil, Jindřich
The main object of the present investigation is to test the settling abilities of mixtures of solid particles in liquids. The key quantity here is the magnitude of the viscosity, both of the carrying liquid (water-glycerol solutions) and the effective viscosity of the two-phase mixture. Few model systems were used (glass and polystyrene pellets), to study the settling process. The sedimentation were recorded by a video camera and the resulting deposit structure was photographed. Besides, also a real suspension was tested, of geological materials (calcite, quartz, mixed geological powder, etc.). Immersion rotary viscometer Brookfield with special spindles (RVT and V spindles) was used to measure the effective viscosity of the dispersion.
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Viskozitní charakteristiky geologických suspenzí
Kulaviak, Lukáš ; Večeř, Marek ; Růžička, Marek ; Drahoš, Jiří ; Hladil, Jindřich
The system under study was real geological suspension – ground sedimentary rocks of different chemical composition (calcite, quartz, etc.) dispersed in water-glycerol solutions. The reference one-phase system was a Newtonian liquid (glycerine with water). It is problematic to measure the rheology of settling suspensions, so some specific tools must be used. We used the rotating vane rheometry, with the immersion viscometer Brookfield and two spindles V-71 and V-72. The basic rheological data of solid-liquid system are displayed as flow and effective viscosity curves. The obtained results on rheology were related to the settling behaviour of the geological mixtures, namely to the certain kind of the lateral instability.
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Optické sondy a jejich přesnost měření
Vejražka, Jiří ; Večeř, Marek ; Orvalho, Sandra ; Sechet, P. ; Cartellier, A.
The optical probes are commonly used for experimental measurements in gas-liquid multiphase systems. During the measurement, it is evaluated the intensity of the light, which reflects from the tip of the optical fiber placed in the measuring point. From the obtained signals, it is possible to evaluate the bubble residence time, local gas hold-up and it is possible to estimate the size and the velocity of the bubbles. In this study, the signal of the optical probe is compared with the data obtained by direct observation by high-speed camera. It was found that optical probe works well in the case of large and fast moving bubbles. In the case of small and slow bubbles the data measured by optical probe are not usable. The dimensionless criterion for minimal Weber number characterizing the reliability of the probe was derived on the base of motion equation for the bubbles.
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