Particle-fluid dynamics under variable gravity conditions

Crystals grown from specially prepared liquid solutions have important industrial applications. The efficiency of these crystals is usually a function of their size. Therefore, during the synthesis of the crystals, it is important to optimize their size, and to control the defect location and concentration. For this reason, crystals have been grown in space in order to take advantage of the reduced gravity. In this paper we describe the macroscopic fluid-crystal dynamics under various microgravity conditions in a three-dimensional cubic reactor. The process is modeled using the conservation of mass and momentum equations for the fluid phase and a discrete particle model for crystals. Solutions are obtained with a finite element implementations in three dimensions. The methodology is validated through comparisons with an analytic solution of crystals settling in a long reactor. Simulations are presented for various initial distributions of particles and gravity levels. The results show the formation of large recirculating zones induced by the settling of particles in the case of a Gaussian initial distribution. For a random initial distribution of crystals the fluid motion is not organized in coherent structures.