Direct Numerical Simulation of Fluid Flow and Mass Transfer in Particle Clusters

Abstract

In this paper, an efficient ghost-cell based immersed boundary method is applied to perform direct numerical simulation (DNS) of mass transfer problems in particle clusters. To be specific, a nine-sphere cuboid cluster and a random-generated spherical cluster consisting of 100 spheres are studied. In both cases, the cluster is composed of active catalysts and inert particles, and the mutual influence of particles on their mass transfer performance is studied. To simulate active catalysts the Dirichlet boundary condition is imposed at the external surface of spheres, while the zero-flux Neumann boundary condition is applied for inert particles. Through our studies, clustering is found to have negative influence on the mass transfer performance, which can be then improved by dilution with inert particles and higher Reynolds numbers. The distribution of active/inert particles may lead to large variations of the cluster mass transfer performance, and individual particle deep inside the cluster may possess a high Sherwood number.

Direct numerical simulation of mass transfer in bidisperse arrays of spheres

“…We refer the interested reader to our earlier paper for a detailed description of the IBM methodology which applies this second‐order quadratic interpolation scheme for the reconstruction procedures . The IBM we developed is able to handle mixed boundary conditions, and we also refer the interested reader to our earlier papers demonstrating the potential for different applications . It should be noted that although only the Dirichlet boundary condition (which can be handled by less complex directional quadratic interpolation scheme) is used in the current study, it has been demonstrated that the quadratic interpolation scheme possesses a better performance at higher Reynolds numbers due to its three directional reconstruction procedures…”

Direct Numerical Simulation of Reactive Fluid–Particle Systems Using an Immersed Boundary Method

“…A finite difference scheme is used to solve the aforementioned governing equations on a 3D staggered Cartesian grid with a uniform grid spacing in all directions. Following our previous work, 30 , 43 the numerical solution of these equations is acquired by embedding second-order discretization schemes as well as compact computational stencils. The momentum, species, and thermal energy conservation equations are discretized temporally by applying the Adams–Bashforth scheme for the convective transport and the Euler backward scheme for the diffusive transport: In these equations, n is the time step index.…”

“…38−41 In their work, flow, heat, and species transport in fixed-bed reactors are modeled, as well as the intraparticle variations accounted for by the solid-particle method. 42 Building on our previous study, 30,31,43 a DNS methodology which is based on an efficient ghost-cell based IBM is extended to the simulation of reactive fluid−particle systems. The coupling of heat and mass transfer arises as a consequence of an exothermic chemical reaction proceeding at the exterior surface of the particles that the particle temperature is increased by the liberated reaction heat and subsequently transfers the thermal energy to the fluid phase.…”

Direct numerical simulation of fluid flow and dependently coupled heat and mass transfer in fluid-particle systems

“…In this paper, we extend an earlier reported DNS model (Lu et al, 2018a;Lu et al, 2018b;Lu et al, 2018c;Lu et al, 2018d) to simulate coupled heat and mass transfer processes in reactive fluid-solid systems. With our ghost-cell based immersed boundary method, the fluid-solid coupling is realized by a second order quadratic interpolation scheme.…”