十字交差2円柱から流出する縦渦の特性

概要

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The behavior of the longitudinal vortices shedding from a cruciform arrangement of two circular cylinders with an equal diameter d is investigated using a wind tunnel. The longitudinal vortices shed periodically near the crossing corner of the cylinders when the gap s between them is less than d/2. The nondimensional shedding frequency, S_<tM>, of the longitudinal vortices is independent of the Reynolds number Re when 730<Re<34,400. The value of S_<tM> is : 0.06<S_<tM><0.09 when s/d<0.25 and S_<tM>≅0.04 when 0.25<s/d<0.5. The fluctuating lift force on the upstream cylinder caused by the longitudinal vortices is estimated from the pressure measured on the cylinder surface. The result correlates well with values obtained from the oscillation amplitude of an elastically supported upstream cylinder. Effects of the oscillation of the upstream cylinder on the longitudinal vortex shedding are also investigated, and a phenomenon similar to the "lock-in" of the Karman vortex shedding is found in certain ranges of s/d and the free-flow velocity.
1992-05-25