Study on improvement of constitutive equations and numerical methods for three-fluid model

The Japan Society of Multiphase Flow*; Special Committee for Examination of Thermohydraulic Analysis Code based on Three-Fluid Model*

The purpose of the present study is to improve a numerical method for multiphase flows based on the three-fluid model. Conducted were (1) improvement of a numcrical scheme, (2)examination on the validity of governing equations, (3)survey and verification of available constitutive equations, (4)development of theoretical constitutive equations and (5) numerical analyses of experimental database on steam-water and air-water annular-mist flows. As a result, the following conclusions were obtained: (a)multi-fluid modelling for all flow regimes were completed, (b)numerical stability of the three-fluid model was clarified, (c)stability-enhanced solution method was developed, (d)a physically-rational and well-posed multi-fluid model was proposed for dispersed flows, (e)systematic survey and evaluation of available constitutive equations for entrainment was conducted and summarized, (f)a theoretical method for the evaluation of film thickness and interfacial shear stress was presented, and(g)it was confirmed that FIDAS-1DS can accurately predict critical heat fluxes under atmospheric pressure, and that it can give qualitatively good predictions conserning film thickness, droplet flow rate and so forth of the air-water annular-mist flow.