The flow patterns around two-dimensional circular cylinder and square cylinder were visualized by the hydrogen bubble technique in case of the relatively low Reynolds number (Re =600700) when the cylinder was installed near the plane wall. The wake of the cylinder varied from a type of the separation bubble to Kármán vortex street when the gap ratio (= gap/diameter of the cylinder) increased. Kármán vortex street occured at the smaller gap ratio as the blockage ratio increased. This gap ratio of the circular cylinder, the occurrence point of Kármán vortex street, was smaller than that of the sauare cylinder.

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