An analysis of fluid damping in two-phase air-water cross flow

Fluid damping of vibrating tubes in two-phase air-water mixtures is discussed in this paper. In single phase fluid, the damping effect of the fluid is due to viscosity. In two-phase mixtures, it is generally admitted that a specific two-phase mechanism of damping appears in addition to the classical viscous damping. Yet, in such models, some difficulties may arise in the definition of the viscosity of the two-phase mixtures. We propose here to consider damping effect of the two-phase mixture as a global entity that includes both viscous and specific two-phase parts. Experimental data in air-water from the literature and from a new test program are analysed in this approach. The effect of the mixture density and of the tube diameter are analysed. It is found that the global fluid damping is dependent on mass flux. A fluid damping in still fluid is defined by extrapolation, for use of the prediction of fluidelastic instability. This approach is compared with previous studies.