Flow of non-Newtonian fluid in a concentric annulus with rotation

환형관내 비뉴튼유체의 회전유동에 관한 연구

This Experimental study concerns the characteristics of vortex flow in a concentric annulus with a diameter ration of 0.52, whose outer cylinder is stationary and inner one is rotating. Pressure losses and skin-friction coefficients have been measured for fully developed flow of bentonite-water solution(5%) when the inner cylinder rotates at the speed $0{\sim}400rpm$. The results of present study reveal the relation of the bulk flow Reynolds number Re and Rossby number $R_o$ With respect to the skin friction coefficients. The effect of rotation on the skin friction coefficient is significantly dependent on the flow regime. In all flow regime, the skin friction coefficient is increased by the inner cylinder rotation. The critical (bulk flow) Reynolds number $Re_c$ decreases as the rotational speed increases. Thus, the rotation of the inner cylinder promotes the onset of transition due to the excitation of Taylor vortices.