**作者：**Jiahn-Horng Chen**中文摘要：**In the literature, the separation of a uniform flow past a circular cylinder is a classical problem. Traditionally, most studies were conducted in an unbounded flow domain, which introduces insurmountable difficulties into the analysis from the theoretical and numerical points of view. The present study was carried out in domains bounded by two parallel plates, and the effects of three different sets of boundary conditions on the flow development were explored. The first two sets of boundary conditions represent infinite and semi-infinite channel flows disturbed by the presence of a cylinder, respectively. The third one represents a lateral domain truncation usually encountered in computations of external flows. A comparison between these two categories reveals that the specification of boundary conditions does not significantly affect the onset Reynolds number of the recirculating eddy. However, under the third set of boundary conditions, the development of separation bubbles is slightly nonlinearly related to the Reynolds number and the onset separation Reynolds number. In addition, the growth of the separation bubbles varies significantly for different boundary setups and diameter-to-width ratios.**英文摘要：**--**中文關鍵字：**laminar separation, boundary conditions**英文關鍵字：**--