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Estimation of turbulence dissipation rate by Large eddy PIV method in an agitated vessel
Kysela, Bohuš ; Jašíková, D. ; Konfršt, Jiří ; Šulc, R. ; Ditl, P.
The distribution of turbulent kinetic energy dissipation rate is important for design of mixing apparatuses in chemical industry. Generally used experimental methods of velocity measurements for measurement in complex geometries of an agitated vessel disallow measurement in resolution of small scales close to turbulence dissipation ones. Therefore, Particle image velocity (PIV) measurement method improved by large eddy PIV approach was used. Large eddy PIV method is based on modeling of smallest eddies by a sub grid scale (SGS) model. This method is similar to numerical calculations using Large Eddy Simulation (LES) and the same SGS models are used. In this work the basic Smagorinsky model was employed and compared with power law approximation. Time resolved PIV data were processed by Large Eddy PIV approach and the obtained results of turbulent kinetic dissipation rate were compared in selected points for several operating conditions (impeller speed, operating liquid viscosity).
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Effect of ultrasound pulsations on suspension sedimentation
Suchánková, A. ; Kysela, Bohuš ; Chára, Zdeněk ; Ditl, P.
The paper presents results of a gravity settling of a model suspension. Experiments have been carried out for two configurations. The first experiment involved natural gravity settling; in the second case the ultrasound pulsations were introduced. Ultrasound field was provided by 20 kHz horn acting through a wall of settling vessel. Three kaolin suspensions of volume concentrations 3.8; 7.6; 11.4 % were used. It has been found that there is no significant influence of ultrasound pulsations on suspension settling.
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Image analysis in an agitated particle - liquid transparent system
Ditl, P. ; Severa, Miroslav ; Šedivý, V.
Large tall vessels with a draught tube are used for the mixing of suspensions especially in cases where high homogeneity and heat tranfer are desirable. The article describes flow behaviour of liquid in the vessel with a draught tube. LDA method (Laser Doppler Anemometry) was used for measurement axial velocity profile. The experimental configuration for LDA method was produced by firm DANTEC. Experimental results are compared with numerical simulation and other experiment.
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