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DYNAMICS OF LARGE- AND SMALL-SCALE VORTICAL STRUCTURES IN TURBULENT TAYLOR-COUETTE FLOW

Naoya Fukushima
Department of Mechanical and Aerospace Engineering, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550, Japan; Frontier Research Center for Energy and Resources, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, Japan; Department of Prime Mover Engineering, Tokai University, 4-1-1, Kitakaname, Hiratsuka-shi, Kanagawa, Japan

T. Fushimi
Department of Mechanical and Aerospace Engineering Tokyo Institute of Technology 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550, Japan

Masayasu Shimura
Department of Mechanical and Aerospace Engineering Tokyo Institute of Technology 2-12-1 Ookayama, Meguro-ku, Tokyo, 152-8550, Japan

Mamoru Tanahashi
Department of Mechanical and Aerospace Engineering Tokyo Institute of Technology 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550, Japan

Toshio Miyauchi
Dept. Mechanical and Aerospace Eng., Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8552, Japan; Organization for the Strategic Coordination of Research and Intellectual Properties Meiji University 1-1-1 Higashimita, Tama-ku, Kawasaki, Kanagawa, Japan

Аннотация

Direct numerical simulations (DNSs) of turbulent Taylor-Couette flow have been carried out for Re = 2000 ~ 12000 to clarify turbulence transition and dynamic characteristics of large vortical structures and fine scale eddies. To investigate effects of the computational domain size, the length of the computational domain in the axial direction is selected to be 4d, 5d and 20d, where d is gap width. At the highest Reynolds number, in addition to fine scale eddies elongated in the azimuthal direction, fine scale eddies parallel to the axial direction are also formed. Dynamic interactions between large- and small-structures are investigated. When the fine scale eddies parallel to the axial direction are strongly stretched in the sweep regions, the fine scale eddies in the azimuthal direction are concentrated in the outflow region near the inner wall and in the inflow region near the outer wall. In contrast, when the fine scale eddies parallel to the axial direction are decreased, the fine scale eddies in the azimuthal direction are expanded. These results suggest that the strength of Taylor vortices is fluctuated temporally and spatially. In the largest computational domain case, the strength of Taylor vortices is fluctuated spatially and Taylor vortices bifurcate and merge at Re = 8000. These phenomena are observed only at higher Reynolds numbers. The process of bifurcation and merge of Taylor vortices are also revealed.