Topology and dynamics of streakline on the mixing boundary of two-dimensional chaotic flow induced by a rotationally reciprocating anchor impeller

Abstract

BackgroundA rotationally reciprocating impeller separates the horizontal cross-section of the vessel into two mixing regions under a laminar flow regime. In this study, we investigated the separation mechanism from the dynamics of the streakline on the boundary MethodsThe stretching behavior of the streakline on the universal boundary of active mixing regions was successfully visualized by injecting tracer fluid from a specific position FindingsThe elongational rate of streakline proportionally increased with the increase in Reynolds number. Besides, the linear component of the elongation rate drastically changed at Re∼10 due to the bending of the boundary. Compared with other chaotic mixing flows, we proved that tracer particles are enclosed in turnstile lobes at the hyperbolic fixed point at the wall, transported on the boundary, namely separatrix, to the mixing shaft being another hyperbolic fixed point, and then distributed evenly into both mixing regions. It was concluded that the boundary becomes wavy at Re > 10, which increases the area of turnstile lobes to enhance fluid transportation between two mixing regions