Fluid-Elastic Vibration of Cross-Shaped Tube Bundle in Mixed Cross and Parallel Flow: Measurement of Gap Flow Velocity and Vibration Characteristics

Abstract

A cross-shaped control rod guide tube bundle is proposed for the lower plenum structure in the next-generation LWR, ABWR-II. In our previous studies, we measured the local fluid excitation forces acting on a cross-shaped tube bundle as well as the self-excited vibration characteristics in pure cross flow in water tunnel tests. In the reactor conditions, the flow field around the tube bundles contains mixed cross and parallel flow components. In this study, water tunnel tests under mixed cross and parallel flow conditions were preformed to understand the influence of the balance of parallel and cross flow components on vibration response. The distributions of the flow direction and flow velocity in the gap between the adjacent tubes were measured with circular Pilot tubes in detail. It was found that the critical flow velocity of self-excited vibration was not influenced by the parallel flow component, but depended only on the cross flow component.