EXPERIMENTAL INVESTIGATION ON ORDERED AND CHAOTIC PHENOMENA OF VORTEX SHEDDING IN THE WAKE FLOW BEHIND A TWO-DIMENSIONAL CIRCULAR CYLINDER

<正> In this paper, some preliminary experiments of ordered and chaotic vortex sheddingsbehind a 2--D circular cylinder at Reynolds numbers ranging from Re=50 to 400 are presented.A transition in vortex shedding from the laminar to chaotic state occurs at Re=184.6-193.5,but it is seemingly not through the quasi--periodicity routes. There is a couple of dis-continuities in slope on the curve of the relationship between the vortex shedding frequencyand Reynolds number. The discontinuity at Re = 70 might correspond to the change of themode of the oblique vortex shedding. The second one at Re = 193.5 is responsible for thetransition from the ordered to the chaotic state.