Experimental Study on the Helical Flow Field in a Concentric Annulus with Rotating Inner Cylinders

Title & Authors
Experimental Study on the Helical Flow Field in a Concentric Annulus with Rotating Inner Cylinders
Hwang, Young-Kyu; Kim, Young-Ju;

Abstract
This experimental study concerns the characteristics of a transitional flow in a concentric annulus with a diameter ratio of 0.52, whose outer cylinder is stationary and inner one rotating. The pressure drops and skin-friction coefficients have been measured for the fully developed flow of water and that of glycerine-water solution (44%) at a inner cylinder rotational speed of $\small{0{\sim}600}$ rpm, respectively. The transitional flow has been examined by the measurement of pressure drops and the visualization of flow field, to reveal the relation of the Reynolds and Rossby numbers with the skin-friction coefficients and to understand the flow instability mechanism. The present results show that the skin-friction coefficients have the significant relation with the Rossby numbers, only for laminar regime. The occurrence of transition has been checked by the gradient changes of pressure drops and skin-friction coefficients with respect to the Reynolds numbers. The increasing rate of skin-friction coefficient due to the rotation is uniform for laminar flow regime, whereas it is suddenly reduced for transitional flow regime and, then, it is gradually declined for turbulent flow regime. Consequently, the critical (axial-flow) Reynolds number decreases as the rotational speed increases. Thus, the rotation of inner cylinder promotes the early occurrence of transition due to the excitation of taylor vortices
Keywords
Transition;Concentric Annulus;Helical Flow;Pressure Loss;Critical Reynolds Number;Rossby Number;
Language
Korean
Cited by
1.
안쪽 축이 회전하는 환형관내 천이유동에 관한 연구,김영주;황영규;우남섭;

설비공학논문집, 2002. vol.14. 10, pp.833-843
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