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The paper concerns the characteristics of transitional flow of non-Newtonian fluids in a concentric annulus with a diameter ratio of 0.52, whose outer cylinder is stationary while inner one is rotating. The pressure losses and skin friction coefficients have been measured for the fully developed flows of 0.2% aqueous solution of sodium carboxymethyl cellulose (CMC) at inner cylinder rotational speed of 0~600 rpm. The transitional flow has been examined by the measurement of pressure losses and visualization of flow fields to reveal the relationship between the Reynolds and Rossby numbers in relation to the skin friction coefficients and to understand the flow instability mechanism. The occurrence of transition has been checked by the gradient change of pressure losses and skin-friction coefficients with respect to the Reynolds numbers. Consequently, the critical Reynolds number decreases as the rotational speed increases. Thus the rotation of inner cylinder promotes the onset of transition due to the excitation of Taylor vortices.
본 논문은 안쪽 실린더가 회전하고 바깥쪽 실린더가 고정된 반경비가 0.52인 동심환형관내 비뉴튼유체의 천이유동 특성을 관찰했다. 안쪽실린더가 0~600 rpm으로 회전하고 0.2% CMC 수용액을 완전히 발달된 유동에서 압력강하와 표면마찰계수를 측정하였다. 천이유동은 표면마찰계수에 대한 레이놀즈수와 로스비수 관계 및 유동의 불안정성 메카니즘을 나타내기 위해 압력강하를 측정하였다. 천이의 발생은 레이놀즈수에 관해 압력손실과 표면마찰계수의 구배변화에 의해 조사했다. 결과적으로 임계레이놀즈수는 회전속도가 증가함에 따라 감소함을 알 수 있다. 따라서 안쪽실린더의 회전은 Taylor 와류의 자극 때문에 천이의 시작을 촉진시킨다.
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- Publisher :The Korean Society of Mineral and Energy Resources Engineers
- Publisher(Ko) :한국자원공학회
- Journal Title :Journal of the Korean Society for Geosystem Engineering
- Journal Title(Ko) :한국지구시스템공학회지
- Volume : 44
- No :5
- Pages :376-382
Journal of the Korean Society of Mineral and Energy Resources Engineers
