Darth Maul In A Stirred Tank
This figure shows an experiment in which fluorescent dye is injected near the center of a stirred tank of glycerine and the tank is illuminated from the side by a vertical laser sheet. The tank is stirred at Reynolds number 30 by two sets of impellers, visible as superimposed gray squares: one beneath the 'nostrils' of the pattern, and one above its 'eyes.' The oscillatory lobes of dye emanating from the impeller blades are hallmarks of a chaotic mixing process. The vanes of the upper impeller are uniformly spaced, producing simply periodic lobes, while the vanes of the lower impeller are unevenly spaced, producing repeated 'm'-shaped lobes. This figure provides graphic evidence that it is the 3-Dimensional enfolding of fluid around the impeller vanes that leads to chaos and mixing in this common industrial mixer. Indeed, careful accounting of the energy expenditure in this system reveals that 90 percent of the kinetic energy present is associated with large-scale recirculating, nonmixing, flows (evident here as the open, black, island structures), and only 10 percent of the kinetic energy generates measurable mixing.
Image credit: M.M. Alvarez-Hernandez, F.J. Muzzio, Troy Shinbrot; ERC for Structured Organic Composites for Pharmaceutical, Nutraceutical and Agrochemical Applications