Buffeting lift forces and local air-water flow aspects around a rigid cylinder

A new experimental programme is conducted in order to relate the characteristics of two-phase flow around a rigid cylinder with the resulting lift forces. The local characteristics of air-water flow measured in the vicinity of the cylinder provide a useful source of information about the effects of flow on the excitation mechanisms. In particular, a selection of relevant parameters has been identified which, with the help of a standard dimensional analysis, may explain the energetic contents of buffeting forces. Among the parameters effective in reducing the data are the flow regime, bubble frequency and gravity forces. In addition, in the range of bubbly regimes, the magnitude of the random forces is found to be related to the local fluctuations of void fraction. Finally, a new formulation is proposed to collapse the dimensionless spectra of the buffeting lift forces in a single characteristic curve. This analysis shows a marked improvement over the collapse of data in comparison with previous normalized models. (authors)