High-Schmidt number turbulent mixing as an aggregation process

• Applicant: Professor Dr. Jörg Schumacher
• Subject Area: Fluid Mechanics ; Statistical Physics, Nonlinear Dynamics, Complex Systems, Soft and Fluid Matter, Biological Physics
• Term: from 2014 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 258767971

The mixing of passively advected substances in turbulent flows is a fundamental process omnipresent in many geophysical, industrial, natural or man-made applications. The interplay between the motions of the underlying stirring field and the ultimate diffusive process is non-trivial when the diffusivity of the mixed scalar concentration is smaller than the kinematic viscosity of the advecting fluid, the so-called Batchelor regime at Schmidt numbers much larger than unity. In this regime, the concentration field self-organises, below the size of the smallest eddies of the velocity field, as a set of sheets, aggregating as they fade away, thus building up the concentration content of the mixture. In the present project, we want to combine laboratory experiments and direct numerical simulations in order to explore in more details this vision of mixing as an aggregation process, and extend it to the three-dimensional case. The impact of different scalar sources as well as of different Schmidt and Reynolds numbers will be studied systematically, both in experiment and simulation, in flow configurations kept as simple as possible, in order to address the fundamentals of the overall process. The goal will be a complete description of the scalar statistics in the viscous-convective range at high Schmidt numbers on the basis of the aggregation model.

• DFG Programme: Research Grants
• International Connection: France
• Participating Person: Professor Dr. Emmanuel Villermaux