In this paper we describe the flow around two-dimensional circular cylinder bundles supported by wires. The experiment was carried out in an N. P. L. blow-down wind-tunnel with a 500mm X 500mm X 2000mm working section, and with Reynolds number 9.4 X 103. The displacement of a vibrating circular cylinder, and the fluctuating pressure distributions on the surface of the circular cylinder were measured. It was found that (i) the critical value of the fluid elastic vibration occuring is obtained as the spacing ratio D/S for a single row, two rows and three rows, (ii) the fluctuating pressure distribution on the surface, fluctuating drag and fluctuating lift by natural frequency increase rapidly beyond the critical value mentioned in (i), and (iii) the variation of fluctuating drag and fluctuating lift corresponds to that of the displacement of a vibrating cylinder.
