Sequential steady state co-rotating dust vortices in sheared streaming plasma

Abstract

The 2D hydrodynamic model for a dust cloud confined in an axisymmetric toroidal system volumetrically driven by an unbounded streaming plasma is further extended systematically for different aspect-ratio of the bounded dust domain and a wide range of the kinematic viscosity. This work has demonstrated the interplay between inertial and diffusive transport processes for the structural changes of steady dust flow from symmetric into asymmetric nature in higher Reynolds number (Re) regimes where flow streamlines turn more circular and the structural bifurcation takes place through a threshold parameter. In agreement with many experimental observations, the steady vortex structure in highly nonlinear (i.e., high Re) regime is characterized by the critical transition into a new self-similar multiple co-rotating vortices, along with circular core region of single characteristics size and surrounded by strongly sheared layers filled with weak vortices near the boundaries. It is further revealed that the core region persists for a wide range of system parameters in the nonlinear regime and its characteristic size is mainly determined by the smallest distance between the confining boundaries. The threshold parameter, the vortex size, the strength, and the number of the self-similar co-rotating vortices mainly depend on the aspect-ratio of the bounded dust domain. These nonlinear solutions provide insight into the phenomena of the structural transition and coexistence of self-similar steady co-rotating vortices in dusty plasma experiments as well as many relevant complex driven-dissipative natural flow systems.