Flow-induced vibration characteristics of cross-shaped tube bundle. Clarification of basic vibration characteristics in cross flow

The applicability of the cross-shaped tube bundle is examined for the reason of making the plant compact in the next generation LWR. The flow-induced vibration characteristics are not understood well. So, the vibration characteristics in the cross flow, where the vibration amplitude was said to be relatively large, was examined by small-scale experiments. The dimensionless correlation equation of fluid excitation force acting on the cross-shaped tube was proposed, which was able to be used to evaluate the vibration amplitude. Since a typical peak to the vortex induced vibration was not seen in the power spectral density of the fluid excitation force, the vortex-induced vibration could not be generated. The self-excited vibration of the torsional mode was found to be generated from the vibration response experiment of the cross-shaped tube bundle when reduced flow velocity was above a certain valued. If the above-mentioned results are used, the flow-induced vibration characteristics of cross-shaped tube bundle in the cross flow can be preliminary evaluated. More detailed characteristics of the critical flow velocity of the bending vibration, the configuration of the bundle, and the influence of the Reynolds number, etc. will be examined experimentally for the self-excited vibration in the future. (author)