STUDY ON THE VIBRATIONAL CHARACTERISTICS OF A TUBE ARRAY CAUSED BY 2-PHASE FLOW .2. FLUIDELASTIC VIBRATION

Fluidelastic vibration of tube arrays caused by two-phase how has been studied before. The critical flow velocity is usually estimated with a simple Conners-type criterion which is based on an average flow velocity, an average fluid mass density and damping in two-phase flow. However, there is no explanation of why this simple criterion is applicable or how fluidelastic instability occurs in two-phase flow. This paper presents experimental results on the fluidelastic vibration caused by air-water flow and by steam-water two-phase flow in conditions of up to 7.0 MPa pressure and temperatures reaching 284 degrees C. A new criterion, based on an assumption of energy balance per cycle of oscillation, is introduced using the ''true'' how velocity. However, comparison with the experimental data indicates that, in the slug or froth flow regimes, the speed of the intermittently rising slugs, introduced in Part I of this study, should be used; hence, a new modified criterion for the slug and froth flow regimes is derived. In addition, the new criterion is compared with the usual Conners-type criterion which greatly depends on the estimation of the damping in two-phase flow. The agreement between the two criteria is found to be within the uncertainty introduced by the variance in the unknown parameters in the Conners criterion. (C) 1995 Academic Press Limited