A simplified procedure to identify trailing vortices generated by a Rushton turbine

Study of fluid flow in baffled vessels stirred by a Rushton standard impeller

“…For 2D PIV measurements the identification of the trailing vortices is based on a procedure suggested by Escudié and Liné [12]. For plane measurements only four components of the gradient velocity tensor could be measured: two diagonal components and two non-diagonal components.…”

“…Any point belongs to the vortex region if the second eigenvalue of the tensor S 2 + 2 (deformation shear tensor 2 + rotation rate tensor 2 ) is negative. This procedure was originally developed for 3D data, but Escudié and Liné [12] the third velocity gradient tensor component based on application of the continuity equation. Using this method with only twodimensional data they obtained very similar results when compared with tip vortex identification based on three-dimensional data.…”

Effect of blade modifications on the torque and flow field of radial impellers in stirred tanks

“…Examples of these lines can be seen in fig 5. In this way the quantities are plotted in the most energetic region of the plane, covering the two vortices and jet region in a similar manner for each blade type. The vortex cores were located by using a simplified version of the λ 2 criterion, introduced by [20], and applying it to the averaged flow fields, but with the actual velocity vectors being replaced by unit vectors, keeping the same orientation as the original. In that way the λ 2 criterion avoided locating points with high shear [21].…”

Structure of turbulent velocity field in the discharge stream from a standard Rushton turbine impeller

“…The basic mixing zone (impeller zone) is a region where the trailing vortices disintegrate. The trailing vortices, which play a crucial role in radially agitated systems, have been observed and described by many research studies [4,13,[18][19][20][21]. The agitated system with radial impeller was also investigated by CFD simulations [4,8,[22][23][24][25]37] where similar results were obtained, but validated namely only in impeller blade vicinity, where the discharged stream analogy was established.…”

“…Although the vortex structures are broken up during the movement and the velocity magnitudes of periodic component decrease, they are finally destroyed on the vessel wall and baffles. The observed length of resulting trailing vortex primarily depends on the identification technique setup [18,20,35] and whether the velocity data are phase-averaged or instantaneous [30].…”