关键词: 泡状流, 双流体模型, 单元系综平均, 压力场

Abstract: Bubbly flow is a basic two-phase flow problem and is usually analyzed using two-fluid models. The closure laws are very important and determine accuracy of two-fluid models. The previous closure laws were derived based on the potential flow assumption, such as the averaged pressure difference, pli-pl, between the interface and the liquid phase. However, the pressure difference is affected by fluid viscosity, wake of bubbles, bubble deformation, and so on. In this paper, taking fluid viscosity into consideration, the pressure difference is constituted using cell-ensemble average. The new formula can be applied for"laminar"bubbly flows where the relative Reynolds number is small and therefore the influence of bubble wakes on the pressure field is negligible. The new formula gives a larger result than the potential one, which agrees with the empirical data for"laminar"bubbly flows. The new formula can not be applied for turbulent bubbly flows, because the pressure field is considerably affected by wakes of bubbles. So it is necessary to investigate the effects of wakes of bubbles to construct a pressure difference formula for turbulent bubbly flows.

Key words: bubbly flow, two-fluid model, cell-ensemble average, pressure field