RÉSUMÉ

The closure of the two-fluid models requires the knowledge of wall and interfacial frictions; however, limited understanding is available. This study therefore revisits this problem by conducing a variety of experiments in an air-water duct flows (see part I). The interfacial and wall shear stresses in gas and liquid phases, together with average value of the RMS wave height and wave spectra are measured and presented in detail. The wall shear stress in two-phase flows is found to be well predicted by the classical laws used in single-phase flow. However, the interfacial friction factor in a wavy-interface flow shows an increasing and then flattened behaviour as the gas velocity increases, which cannot be predicted by the previous models. A basic theory is then proposed based on the hypothesis on wave number spectra in internal flows to interpret this observation.