Hydrodynamic and Hydraulic Studies on Void Fractions in Two-Phase Flow

For gas-liquid two-phase flow, two kinds of fundamental equations have been proposed by the methods of hydrodynamics and hydraulics. The hydrodynamic equation, to avoid analytical difficulties, does not deal with two-phase flow itself, but with a hypothetical liquid flow which has actual physical quantities in the region where the liquid phase really exists and has the imaginary physical quantities of liquid in the region where the gas exists, for each instant, and with a hypothetical gas flow similarly. The hydraulic equation differs from the usual form in the treatment of friction term or interaction, and has better physical insight. These equations are analyzed mathematically and some relationship between physical quantities centering void fraction are discussed. Hydrodynamic equation shows the void fraction distribution to have relation to pressure loss and velocity distributions, and, for the case of laminar two-phase flow with axial symmetry, explicit expression is presented. By hydraulic equation, the relation between void fraction and other variables are discussed. For the upward two-phase flow with constant flow area, gas-liquid interaction force is discussed theoretically and experimentally.