Influence of laser thickness on the determination of solid volume fraction in refraction index matching experiments

Refraction index matching (RIM) method is widely used in the studies of the particle-liquid flows. However, the determination of the solid volume fraction φ based on the RIM imaging indicators has not been well studied. Based on discrete element methods and virtual sampling and projection process, this paper studies the influence of the laser thickness on the prediction models of φ and the model parameters based on the area fraction c2D and the size of the Voronoi diagram dpoly. It is found that the traditionally used proportional function of c2D - φ holds only when the laser thickness H is infinitely small. When H is not negligible compared to the particle size, a linear model should be adopted whose intercept increases with H. The variation of the model parameters based on dpoly under different H is also obtained and the exponent agrees well with the experimental result.