Influence of Stochastic Effects on Flow Induced Vibrations in Tube Bundles

Abstract

There are different excitation mechanisms that cause fatal damages in heat exchanger tube bundles subjected to cross-flow, cp. Weaver & Fitzpatrick [27]. In the present paper the two most important mechanisms are considered, i.e. fluidelastic instability and turbulent buffeting. These mechanisms which can be investigated separately influence each other. Particularly the intensity of the turbulent buffeting can have a significant influence on the onset of instability. Fig.1a illustrates the experimental determination of the stability threshold for a tube within a bundle. Here, the amplitude â related to the tube diameter d is plotted in dependence of the reduced gap velocity V,. (Figure la). A reliable determination of stability boundaries requires a stability criterion, cf. Chen [11]. In this study the amplitude criterion used also by Austermann & Popp [8] has been applied. A sudden change of small amplitudes due to turbulent buffeting to large amplitudes caused by fluid-elastic instability characterises the stability point that depends on the adjusted damping, described by the mass-damping parameter δ_r (Figure 1b).