Wave phenomena and momentum interaction in two-phase flow

The volume averaged form of the linear momentum conservation equations for two phase flow is examined to clarify momentum interaction effects between phases. Averaging makes the form of the equations more tractable, yet in the process, information regarding spatial distribution and local gradients is lost. To recover this precious information, semi empirical or analytical closure relations also called "constitutive relations" have to be established.; To assess the form of these constitutive relations, we investigate both experimentally and analytically several features of the flow structure: void fraction wave velocity and stability, flow regime transition or most unstable wavelength. The experiments on density wave propagation are conducted by cross-correlating the fluctuating signals from a pair of gamma densitometers. Predictions of wave velocity as well as the onset of wave instability are in good agreement with experimental observation, which enhances our confidence in the proposed model.; The results of this research are expected to improve our confidence in the form of the constitutive relations to be used in predictive computer codes based on the averaged multifield model.