Assessment of Different Cavitation Models in Mixture and Eulerian Framework for Two-Phase Flow in Diesel Injectors

A comparative study using different cavitation models in mixture and Eulerian framework is carried out for the analysis of two-phase flows in diesel injectors. Three different cavitation models are investigated here: recently developed modified single-fluid, Schnerr-Sauer and Zwart-Gerber-Belamri models. The last two models have been implemented in both mixture and Eulerian framework. The numerical predictions are compared both qualitatively and quantitatively with experimental results available in the literature. Qualitative assessments have been carried out with experimental images of two-phase flow in an optically accessible nozzle. Quantitative comparisons have been done with measured mass flow rates and velocity profiles. It appears that at low pressure differentials there can be considerable discrepancy in the predictions of the vapour distribution from the three models considered. The modified single-fluid approach turns out to be comparatively better with respect to the other two models. Implementation in mixture and Eulerian framework yields noticeable differences in the results because of the relative velocity of the two phases. Numerical experiments have been carried out with different two-phase turbulence modelling approaches, pressure-velocity coupling algorithms, gradient calculation methods and under-relaxation factors to assess the robustness of the models. Additionally comparisons have been carried out for conditions under high inlet pressure in an axisymmetric nozzle to understand the performance of the models under realistic operating conditions.