Statistical variation of characteristics of random packed beds of Raschig rings: The influence of the sample size

Abstract Many studies on random packed beds have been dedicated to local porosity (void fraction) or orientation distribution of particles. However, despite the random nature of the considered packings, very little attention has been devoted to examination whether the number of particles used in experiments/simulations is sufficiently large to get reproducible results. The reproducibility of the key packing parameters depends on the size of the population of particles (sample size) and ordering effects induced by the confining walls. This work investigates quantitatively the influence of the sample size on the statistical variation of the packed bed characteristics. Packed beds of Raschig rings were generated with a sequential algorithm and three column diameters were considered. It has been found that in the case of the orientation distribution the results depend strongly on the sample size, especially for slender columns, while the porosity profiles are well-reproducible characteristics even for relatively small packings of rings. Some complementary results for full cylinders are also included.