Direct numerical simulation of solid–liquid–gas three-phase flow: Fluid–solid interaction

A direct numerical simulation (DNS) model for three-phase flow (solid, liquid, and gas) with the main purpose of analysing wet granulation processes is presented in this paper. In the present model, liquid–gas two-phase flow is solved by the constrained interpolation profile (CIP) method developed by Yabe et al. (2001) [1], and the interaction between fluid phases and solid particle phase is taken into account by using the immersed boundary (IB) method developed by Kajishima et al. (2001) [2]. The surface tension as well as the wetting are modelled by using the continuous surface force (CSF) model suggested by Brackbill et al. (1992) [3], and the dynamic contact angle is represented by Fukaiʹs (1995) [4] approach, which selectively uses advancing and receding contact angles depending on the movement of fluid interfaces on a solid surface. The accuracy of the model is examined in terms of (i) the drag force exerted on a single particle, (ii) the drag force exerted on a regular particle array, (iii) the surface tension force, and (iv) the wetting. A number of test simulations have been carried out with different numerical cell sizes, and the results are compared with the reported experimental work and theoretical values.