Abstract
<p>The hydrodynamics and flow field were measured in an agitated vessel using 2-D Time Resolved Particle Image Velocimetry (2-D TR PIV). The experiments were carried out in a fully baffled cylindrical flat bottom vessel 300 mm in inner diameter. The tank was agitated by a Rushton turbine 100 mm in diameter. The velocity fields were measured for three impeller rotation speeds 300 rpm, 450 rpm and 600 rpm and the corresponding Reynolds numbers in the range 50 000 &lt; Re &lt; 100 000, which means that the fully-developed turbulent flow was reached. In accordance with the theory of mixing, the dimensionless mean and fluctuation velocities in the measured directions were found to be constant and independent of the impeller rotational speed. The velocity profiles were averaged, and were expressed by Chebyshev polynomials of the 1<sup>st</sup> order. Although the experimentally investigated area was relatively far from the impeller, and it was located in upward flow to the impeller, no state of local isotropy was found. The ratio of the axial rms fluctuation velocity to the radial component was found to be in the range from 0.523 to 0.768. The axial turbulence intensity was found to be in the range from 0.293 to 0.667, which corresponds to a high turbulence intensity.</p>
Highlights
It is important to know the flow and the flow pattern in an agitated vessel in order to determine many impeller and turbulence characteristics, e.g. impeller pumping capacity, intensity of turbulence, turbulent kinetic energy, convective velocity, and the turbulent energy dissipation rate
The hydrodynamics and the flow field were measured in an agitated vessel using Time Resolved Particle Image Velocimetry (TR PIV)
The ratio of the axial rms fluctuation velocity to the radial component was found to be in the range from 0.523 to 0.768
Summary
It is important to know the flow and the flow pattern in an agitated vessel in order to determine many impeller and turbulence characteristics, e.g. impeller pumping capacity, intensity of turbulence, turbulent kinetic energy, convective velocity, and the turbulent energy dissipation rate. Drbohlav et al [1] made an experimental investigation of the velocity field in the stream discharging from a Rushton turbine at Reynolds numbers Re = 146000 and Re = 166000 They described the axial profiles of the mean velocity components in this region using a phenomenological three-parameter model based on a tangential cylindrical jet, proposed by [2]. (4.) region C, in which the flow direction changes from axial to radial at the vessel bottom or at the liquid surface;. The aim of this work is to study scaling of the velocity field outside the impeller region in a vessel mechanically agitated by a Rushton turbine in a fully turbulent region at a high Reynolds number in the range of 50000 < Re < 100000. The radial profiles of the mean and fluctuation velocities are expressed in terms of Chebyshev polynomials
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