A Study for Wake Characteristics of Flow Around a Heated Circular Cylinder in the Laminar and Transitional Regimes.

• Main Authors: Wu, Ming-Hsun, 吳明勳
• Other Authors: Wang, An-Bang
• Format: Others
• Language: en_US
• Published: 2001
• Online Access: http://ndltd.ncl.edu.tw/handle/15658606094156031872

碩士 === 國立臺灣大學 === 應用力學研究所 === 89 === Flows over a heated circular cylinder at temperature ratio T* between 1 and 2 in the laminar and the transition wake regimes (47<Re<400) have been investigated. The suppression of primary vortex onset at Re ~ 47 by cylinder heating as well as the reduced shedding frequency in the periodic wake regime were confirmed. As for the onset of three-dimensionality in the wake, we found that the onset Reynolds number of three-dimensionality for a heated circular cylinder was higher than that of an unheated one. A reduction in shedding frequency a heated circular cylinder compared with that of an unheated one at the same Reynolds number was also observed in the transition wake regime. The influence of buoyancy on the wake is thought to be much less than the alternation in kinematic viscosity of the fluid in forced convection region. As a result, an “effective” Reynolds number calculated with the kinematic viscosity at an “effective” temperature was defined. Strouhal — Reynolds relationship was generalized for T*=1.1, 1.5, and 1.8 by using this effective Reynolds number throughout the Reynolds number range under investigated. Instead of a recursive calculation of effective critical Reynolds number for defining the effective temperature, more convenient methods for defining the effective temperature were developed.