(139b) Direct Numerical Simulation of Flow and Mass Transfer in Complex Geometries Using a Coupled Volume of Fluid and Immersed Boundary Method

Currently innovative solutions are being sought to enhance the perception of specific tastes by delivering the markers more effectively, without affecting the taste intensity and the consumer preference, for example by creating regions with different concentrations of the tastant in a product. However, solutions for the implementation of a heterogeneous taste distribution are still lacking today, especially in beverage products. Dissolution and distribution of tastants in liquids poses a complex multiphase flow problem. With an exponential increase in the computational power over last few decades, and through a combination of different simulation techniques, Computational Fluid Dynamics (CFD) has been emerging as an effective tool for obtaining in-depth knowledge of the involved scale and phase effects in multiphase flows. The goal of present work is to use a multiscale modeling approach to investigate flow and mixing dynamics of beverages in a cylindrical cup.

In this work, a fully resolved direct numerical simulation of flow and mass transfer are coupled for three-dimensional complex geometries on a non-body conformal Cartesian computational domain. A direct forcing implicit, second-order accurate immersed boundary method (IBM) (Deen et al., 2012) is used to resolve the coupling between fluid phase and solid wall. The fluid-fluid interface is tracked by a mass conservative sharp interface volume of fluid (VOF) method (Baltussen et al., 2017). Moreover, the fluid-fluid interfaces in contact with solid boundaries leads to a three-phase contact line, in addition to the interface motion. An apparent contact angle is imposed as a boundary condition at the three-phase contact line (Patel et al., 2017). A second-order implicit (semi-implicit) method is employed to incorporate the species conservation equation of the fluid in a structured grid. Neumann boundary conditions are incorporated at the fluid-wall interface for mass transfer, while Dirichlet boundary conditions are applied for the coupling between fluid-particle interfaces.

The proposed approach is first applied to simulate the mass transfer of static flow in a complex geometry. The simulation results are validated against corresponding analytical solutions. Furthermore, present model is used to investigate the influence of the tilting motion of the geometry on the resulting mass transfer in the fluid.

Keywords: Direct Numerical Simulation (DNS), Volume of Fluid (VOF), Immersed Boundary Method (IBM), contact line dynamics, mass transfer, tilting

References:

1. Deen, N.G., Kriebitzsch, S.H., van der Hoef, M.A. and Kuipers, J.A.M., Direct numerical simulation of flow and heat transfer in dense fluid–particle systems. Chemical Engineering Science, 81 (2012): 329-344.

2. Baltussen, M. W., Segers, Q. I. E., Kuipers, J. A. M., and Deen, N. G., Cutting bubbles with a single wire. Chemical Engineering Science 157 (2017): 138-146.

3. Patel, H.V., Das, S., Kuipers, J.A.M., Padding, J.T. and Peters, E.A.J.F., A coupled Volume of Fluid and Immersed Boundary Method for simulating 3D multiphase flows with contact line dynamics in complex geometries. Chemical Engineering Science, 166 (2017): 28-41.