Abstract
Basic equations and constitutive equations of gas-liquid two-phase flow were explained based on the various modeling. The local instantaneous formulation and averaged formulation of basic equations were described based on typical models such as homogeneous model, drift flux model and two-fluid model. The constitutive equations for these averaged basic equations were discussed. The modeling of turbulence in gas-liquid two-phase flow were also explained and basic equations and constitutive equations of turbulence were described.