title: Experimental study on dynamics of coherent structures formed by inertial solid particles in three-dimensional periodic flows.
abstract: We present experimental results obtained under normal gravity on the dynamics of solid particles in periodic oscillatory thermocapillary-driven flows in a non-isothermal liquid bridge made of decane. Inertial particles of different densities and in the size range approximately 0.75-75 μm are able to form stable coherent structures (particle accumulation structures, or PASs). Two image processing techniques were developed and successfully applied to compute time required for an ensemble of particles to form a structure. It is shown that the formation time grows with the decrease of the Stokes number. The observations indicate the probable irrelevance of the memory term for these experiments. Two types of PAS were observed-single (SL-I) and double-loop (SL-II)-which sometimes co-existed. Only large or very dense particles may form an SL-II type structure. A number of novel features of the system were perceived. In some cases, intermittently stable structures emerged (their dynamics is characterized by alternating time intervals during which a structure exists and is destroyed). Whereas in most experiments we observed a conventional symmetric and centered PAS, there were cases when a long-term stable asymmetric structure appeared. Experiments wherein two different types of PAS-forming particles were used simultaneously revealed the destructive role of collisions between the particles on formation of structures.
authors.affiliation: Tokyo University of Science, 2641 Yamazaki, Noda, Chiba, Japan.
authors.forename: Masakazu
authors.initials: M
authors.lastname: Gotoda
authors.affiliation: Université Libre de Bruxelles, MRC, CP165/62, Av. F.D. Roosevelt, 50, B-1050 Bruxelles, Belgium.
authors.forename: Denis E
authors.initials: DE
authors.lastname: Melnikov
authors.affiliation: Tokyo University of Science, 2641 Yamazaki, Noda, Chiba, Japan.
authors.forename: Ichiro
authors.initials: I
authors.lastname: Ueno
authors.affiliation: Université Libre de Bruxelles, MRC, CP165/62, Av. F.D. Roosevelt, 50, B-1050 Bruxelles, Belgium.
authors.forename: Valentina
authors.initials: V
authors.lastname: Shevtsova