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As described in my question, these two macros can effectively obtain the interfacial area density (defined using the algebraic method) in two-phase flow problems. The first macro can determine the indices of the interface between the two phases based on the provided information about the two phases. After supplying these indices to the second macro, the interfacial area density of the grid cell can be obtained. UDF validation has been conducted for several typical algebraic definition models, and the results are as follows:

It was found that the Particle and Symmetric models in ANSYS FLUENT have a minimum lower limit for interfacial area density, which is 0.006 m^-1. When the mathematical model calculates a result smaller than this value, it can only return 0.0059999..., and it returns a true value only when the calculated result is greater than this value. Furthermore, there is a slight deviation between the interfacial area density calculated by the UDF for the Gradient model and the values extracted by the macros, the reason for which is currently unknown.

In addition, there is a significant discrepancy between the interfacial area values extracted by the macro and the interfacial area concentration (IAC) model obtained based on the transport equation for the interface. If any of you discover the reasons for the disparity between these two models while using the macro, your guidance would be greatly appreciated. Thank you very much!