Dear sir,

            I have doubts about interfacial  constitutive correlations in two-fluid model. Can we use the empirical correlations  those are used in lumped analysis (porous media approximation, subchannel level analysis of reactor flow channel) as such into CFD code?For ex. interfacial area concentration in lumped analysis codes consider as :  (4*(vapor fraction)^0.5)/Dh   Dh hydraulic diameter. This is  for annular flow regime. But in CFD codes thy give as gradient of vapor fraction as IAC correlation for annular flow regime. What is the difference between both?