(458b) Flow Induced Particle Separation in Turbulent Channel Flow

Particle separation has been an issue in many engineering disciplines and applications, due to purity requirements in pre-treatment processes, or in post-reacting flows. Several methods have been invented, with use of additional equipment, by employing effects of electric field[1, 2], centrifugal force[3, 4] etc. Our study finds that turbulence, which is usually pursued to provide excellent mixing efficiency[5-7], could separate particles with different Schmidt numbers, Sc, with no use of outside force or devices. Direct numerical simulation is used with tracking of scalar markers (Lagrangian scalar tracking, LST) to obtain particle positions as they travel in a flow. Since particles with different Sc have different values of dispersion, mixed clouds of particles, after a long enough time, will result in separate clouds of particles with different Sc. The efficiency of separation is affected by the distance from the wall at which particles are released into the flow and by the difference in Sc between particles. The mechanism for this flow-induced separation will be discussed, and its relation to the development process of instantaneous puffs of particles. Criteria for a successful separation will also be discussed.

References

[1]          X.-B. Wang et al., Anal. Chem. (Wash.) 72 (2000).

[2]          O. Gaal, Electrophoresis in the Separation of Biological Macromolecules (John Wiley & Sons Ltd, 1980).

[3]          L. J. Gimbert et al., Environ. Sci. Technol. 39, 5 (2005).

[4]          S. Juen et al., Superlattices Microstruct. 11 (1992).

[5]          L. Valino, C. Dopazo, and J. Ros, Phys. Rev. Lett. 72 (1994).

[6]          B. I. Shraiman and E. D. Siggia, Phys. Rev. Lett. 77 (1996).

[7]          J. Schumacher and K. R. Sreenivasan, Phys. Rev. Lett. 91 (2003).