Rotating axial flow of a continuously separating mixture

Abstract

We consider the continuous separation process of a monodispersed suspension flowing axially through a rotating circular cylinder. This stationary problem can be regarded as a basic flow case of rotating mixtures in conjunction with previous studies of time-dependent flows like spin-up and batch settling in a cylinder. The ‘mixture model’ for two-phase flow is used to formulate the problem, which is solved in the range of small Ekman and Rossby numbers by asymptotic analytical methods and by a numerical code. The gradual separation of the axially injected suspension is manifested as a stationary stratification of the mixture which induces a swirl component of the velocity, in analogy with the thermal wind in the Earth's atmosphere. The presence of the azimuthal motion and induced secondary flow due to Ekman-layer pumping clearly influences the character of the stratification. Analytical and numerical results are in excellent agreement.