On the Behaviors of a Pair of Line Vortices Approaching a Circular Cylinder: Computation and Experiment

• Main Authors: Chang,Ching-Cheng, 張慶成
• Other Authors: Chu,Chin-Chou
• Format: Others
• Language: zh-TW
• Published: 1994
• Online Access: http://ndltd.ncl.edu.tw/handle/13032090946103046777

碩士 === 國立臺灣大學 === 應用力學研究所 === 82 === A combined numerical and experimental analysis has been car- ried out for investigating the behavior of a pair of line vorti- ces,mutually propelled to approach a circular cylinder. The flow is assumed to be two-dimensional in numerical simulations, and which condition is examined carefully in laboratory experiments. The Reynolds number Re=.kappa./.nu. based on the initial circu- lation .kappa. of the vortices and the kinematic viscosity .nu. of the fluid range from 100 to 1500. The major point of interes- t is the effect of flow separation, which induces formation of secondary vortices, interacting then with the primary vortices. Flow behaviors are identified and classified within different f- low regimes with the help of six types of characteristic trajec- tories associated with the primary and secondary vortices. Of p- articular interest are the phenomena of rebound and reversal, ex- hibited respectively by the primary vortices moving against the cylinder under different flow conditions. Stable pairs of line vortices are generated in laboratory experiments; flow visualiz- ation shows excellent agreement with numerical results in the c- omparisons of global flow behaviors,and in particular trajector- ies of the points of maximum vorticity and those of maximum val- ues of the streamfunction.