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안쪽축이 회전하는 경사진 환형관내 비뉴튼 유체의 헬리컬 유동 연구
김영주(Young-Ju Kim),우남섭(Nam-Sub Woo),권혁정(Hyuk-Jung Kwon),황영규(Young-Kyu Hwang) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.5
This experimental study concerns the characteristics of a transitional flow in an inclined concentric annulus with a diameter ratio of 0.52, whose outer cylinder is stationary and inner one rotating. The pressure losses and skin-friction coefficients have been measured for the fully developed flow of 0.2% aqueous solution of sodium carboxymethyl cellulose (CMC), respectively at inner cylinder rotational speed of 0~300 rpm. The transitional flow has been examined by the measurement of pressure losses to reveal the relation of the Reynolds and Rossby numbers with the skin-friction coefficients. The present results show that the skin-friction coefficients have the significant relation with the Rossby numbers, only for laminar regime. When the inner cylinder rotates, Taylor vortices are brought about in the gap by the action of centrifugal forces increased frictional factor and pressure distribution profile. The increasing rate of skin-friction coefficients due to the rotation in uniform for laminar flow regime, whereas it is suddenly reduced for transitional flow regime and, then, is gradually declined for turbulent flow regime. Consequently, the critical(axial-flow) Reynolds number decrease as the rotational speed increases.