Development of direct simulation models of gas-liquid two-phase flow in nuclear reactors using particle-mesh hybrid method

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Dryout of liquid film is an important issue for design and safety of boiling water reactors. Liquid film flow rate needs to be analyzed for quantitative prediction of this phenomenon. We developed a particle-mesh hybrid method that is capable of analyzing gas/liquid flow and their interaction. Flooding phenomenon in gas-liquid countercurrent flow was analyzed in order to validate this method. Onset of flooding by calculation agreed well with an existing empirical correlation.Heat removal from post-dryout fuel rods by reattaching droplets is also important. We analyzed droplet impact on heated surface and calculated heat removal using a particle method. Firstly, droplet impact was analyzed without evaporation model using various Weber numbers and contact angles. Then, it was analyzed with evaporation model. Calculated droplet shape and its staying time on the heated surface agreed with existing experiences.Droplet entrainment phenomenon from liquid film was analyzed using the particle-mesh hybrid method. We can reproduce this phenomenon for the first time. Onset of entrainment was calculated using various densities, viscosities, surface tension coefficients, gas phase velocities, etc. It agreed well with several existing correlations. However, calculated entrainment ratio did not quantitatively agree with existing correlations. Calculation region and particle number should be increased, which is the future subject.