Numerical Analysis of Droplet Flow Regime in Gas-Liquid Two-Phase Flow using Particle Method

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Two-fluid model has been used for gas-liquid two-phase flow analysis. Governing equations of gas and liquid phases are simultaneously solved with correlations expressing interfacial interactions. These correlations are obtained by experiments. Numerical analysis is difficult for them. In particular, interfacial area is an important parameter to determine the interactions. Grids are not necessary in particle method, so that fragmentation and coalescence of fluids as well as large deformation of interfaces can be analyzed. In the present study, the critical Weber number by which the interfacial area is evaluated in the droplet flow regime is analyzed by the particle method.The particle method used here is MPS (Moving Particle Semi-implicit) method which has been developed by the present researcher. A new model for surface tension is developed to analyze single droplet behavior. Vibration of a square droplet is calculated and the oscillating period agrees with that of the analytical solution. Flow around a droplet is calculated and the pressure distribution on the droplet agrees with those of the past studies. Droplet breakup is driven by the pressure distribution and suppressed by surface tension. Both processes are verified. It is also clarified that more than 100 particles are necessary to analyze the droplet behavior accurately.It is known that the droplet breakup is governed by a non-dimensional number called Weber number, which is the ratio of the driving force to the suppressing force. Critical Weber number gives the limit of droplet breakup. The breakup does not occur when the Weber number is below the critical value. The droplet behavior is calculated for various Weber numbers using the MPS method. The results show that the critical Weber number is 13. This agrees with experimental data. Therefore, it is concluded that the critical Weber number is successfully analyzed by the MPS method.