Analysis on vibration response of U-tube bundles caused by two-phase cross-flow turbulence

In steam generators and other heat exchangers, there are a lot of tube bundles subjected to two-phase cross-flow. The fluctuating pressure on tube bundle structure caused by turbulence can induce structural vibration. The power spectral density (PSD) of buffeting force is usually required as the input of random vibration analysis. Since there is no generally accepted method to compute the normalized buffeting forces, the acknowledged upper bound of buffeting forces due to two-phase flow is absent. This paper presents a new set of upper bound of buffeting forces in two-phase flow by modifying the mixture velocity proposed by de Langre. The new upper bound is compared with the one based on single-phase flow, and de Langre's upper bound when two-phase flow is considered. Through a sample of steam generator tube subjected to non-uniform two-phase cross-flow, the random vibration responses based upon three types of upper bounds are computed. The proposed upper bound lies between the one derived from single-phase flow modeling and the one proposed by de Langre. It turns out that the newly proposed upper bound could cover sufficient experimental data sets of the buffeting force and is below the de Langre's bound over a wide frequency range.