TURBULENCE IN NON-BAFFLED MIXING VESSEL

概要

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Time-mean liquid velocity, RMS velocity, various scales of turbulence, and energy dissipation rate in non-baffled mixing vessel are measured. As the lateral RMS velocity is one-third to one-fourth the longitudinal RMS velocity, liquid in the vessel is in the non-isotropic turbulence field. However, the theory of local isotropy of Kolmogoroff can be applied because existence of the inertial subrange is observed. As the integrated value of local energy dissipation rate agrees with the power per unit mass of liquid from the impeller, almost all energy from the impeller is viscous dissipated in eddies of micro scale. At low impeller speed, there exist poorly turbulent portions at parts distant from the impeller or in motion of micro scale eddies in the high frequency range in spite of the fact that Re number indicates full turbulence. Turbulent diffusivities in radial direction are from 0.1 to 10 cm2/sec in this experiment and are almost proportional to impeller speed. Turbulent diffusivities in tangential direction are three to five times larger than those of radial or axial diffusivities and mixing between cylindrically rotating zone and outer quasi-free vortex zone is poor.
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