Search

In this paper, a hybrid computational technique for the Direct Numerical Simulation of hydrodynamics and (convective) mixing in complex two-phase systems is presented. The hybrid Immersed Boundary and Volume of Fluid method is based upon a single-fluid approach in combination with Henry’s law for the concentration jump. The convective species fluxes are evaluated using PLIC-based geometrical advection, which is consistent with the advection of the local fluid volume fractions. Complex geometries can be accounted for and are treated with the Immersed Boundary method. Following the verification for single phase and two-phase systems, the model was used to investigate the influence of the container geometry on the mixing of a tracer due to tilting of the container. For both cylindrical and rectangular containers, an increasing tilting angle enhances the convective motion and consequently the mixing efficiency. The cylindrical geometry was found to possess a better mixing efficiency than the rectangular geometry. Keywords: Direct numerical simulation, Volume of fluid method, Immersed boundary method, Mass transfer, Henry’s law, Contact line dynamics

This article introduces technical solutions applied in food, pharmaceutical, and chemical industries to enhance flowability and reconstitution of amorphous powders. Growth agglomeration describes the controlled buildup of porous structures by bringing sticky particles in contact with each other. Building on the material science describing glass transition, hygrosensitivity, and viscous flow, an overview is given on common methods to increase adhesion forces effectively by controlling local wetting, gas flow patterns, and powder movement in industrial systems. Three process concepts are compared with respect to the achievable product structure (size, instant properties, and tensile strength) as well as regarding throughput and cost: agglomeration during spray drying, steam jet agglomeration, and fluidized bed agglomeration. Examples are given from the food and beverage industry on typical applications of these processes.