A study of geometrical structure of packed beds using flow simulation with the immersed boundary method

Abstract

In this work, a new method is proposed for calculation of one of the essentials geometrical parameters characterising a packed bed - tortuosity. The geometry of random packings of cylinders and rings (with various packing densities) is numerically generated with Discrete Element Method approach. For flow calculations in a highly complex geometry of a random packed bed, immersed boundary method is employed (with direct forcing variant). The obtained flow velocity field allows for calculation of tortuosity using two methods: by passive advection of massless particles and by comparison of the mean flow velocity magnitude with the mean streamwise velocity component. It is demonstrated that for the packings of low density these two methods are in a good agreement but may diverge for dense packings. Frequency distribution of tortuosity values for individual flow paths is also examined. The results show more frequent occurrence of low-tortuosity paths for coarse packings.