Abstract: The flow pattern between concentric cylinders of micro-filtration membrane separators with the inner cylinder rotating can transform from one kinds of pattern to another at different flow conditions when there are axial flow and radial flow. The discrepancy between the inputted electromagnetic rotational speed and the rotational speed of the electromotor is a token of the flow pattern. Under the constant pressure operation condition, the resistance of membrane separation can be divided into undefiled resistance, irreversible resistance and reversible resistance. The first two resistances can be a constant in a process of very short time, and the reversible resistance is a function of rotation under a regime of certain flow pattern. The flow patterns are divided into four patterns: Couette-Poiseuille flow, random laminar wavy vortices, turbulent wavy vortices and turbulent vortices that have distinct influence on the filtration flux and the membrane separation resistance shown by the experiment. Membrane separation characteristics in each flow pattern is discoursed respectively based on the separation experiment with quartz sand suspension，and turbulent vortices flow patter is at the best for rotary tubular membrane separator.

Key words: Filtration flux, Filtration resistance, Flow pattern, Microfiltration, Rotary tubular membrane separator, Vortices flow