Abstract
The distribution of turbulent kinetic energy dissipation rate is important for design of mixing appa- ratuses 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 turbu- lence 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).
Highlights
Distribution of the turbulence kinetic energy dissipation rate inside an agitated vessel is crucial for better understanding of mixing processes such as dispergation, homogenization etc. and essential for scale-up modelling of large mixing vessels
While formerly a temporal record of instantaneous velocities [3, 12] or two point measurement [9] was used for determination of dissipation rate, nowadays determination from velocity field obtained by Particle image velocity (PIV) method [5,6,8,10,11] is preferred
Comparison of two velocity fields normalised by impeller tip speed is shown in figure 2, where the velocity field of water with impeller speed 300 rpm is compared to the velocity field of MEG1 solution with impeller speed 600 rpm
Summary
Distribution of the turbulence kinetic energy dissipation rate inside an agitated vessel is crucial for better understanding of mixing processes such as dispergation, homogenization etc. and essential for scale-up modelling of large mixing vessels. While formerly a temporal record of instantaneous velocities [3, 12] or two point measurement [9] was used for determination of dissipation rate, nowadays determination from velocity field obtained by PIV method [5,6,8,10,11] is preferred. This trend will be probably continued according to measurement techniques development to fully 3D measurements with resolution up to Kolmogorov scales. We want to investigate and make clear the relation between distribution of dissipation rate inside an agitated vessel and operating conditions for high impeller Reynolds numbers (turbulent regime)
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