Liquid fluidization with cylindrical particles: Highly resolved simulations

Abstract

We perform three-dimensional, time-dependent simulations of dense, fluidized suspensions of solid cylindrical particles in a Newtonian liquid in fully periodic domains. The resolution of the flow field is an order of magnitude finer than the diameter of the cylindrical particles. At their surfaces no-slip conditions are applied through an immersed boundary method (IBM), coupled to the lattice-Boltzmann method that is used as the fluid flow solver. The marker points of the IBM are also used to detect and perform collisions between the cylinders. With these particle-resolved simulations, we study the effects of the aspect ratio of the cylinders and the solids volume fraction on the superficial slip velocity between fluid and solids, on the solids velocity fluctuations, as well as on the orientation of the cylinders. The aspect ratio (length over diameter of the cylinders) ranges from 0.5 to 4, the solids volume fraction goes up to 0.48. Reynolds numbers based on average settling velocity are of the order of 1-10. At constant Archimedes number, we observe only minor sensitivities of the settling Reynolds number on the aspect ratio.

Suspension of flexible cylinders in laminar liquid flow

“…This article extends the simulations on dense liquid‐solids suspensions with rigid particles of cylindrical shape as discussed in References 5 and toward cylinders with a finite bending stiffness. We begin this section with a brief overview of the numerical approach (details in Reference ) and then zoom in on how bending has been implemented as well as discuss the assumptions and limitations of the implementation.…”

“…Therefore, predicting the flow dynamics of fiber suspensions, specifically in complex configurations as often seen in process equipment, has practical relevance. The approach to fiber suspension flow we have taken in recent publications is based on particle‐resolved simulation. Particles of cylindrical shape are placed in a domain containing a Newtonian liquid.…”

“…The previous simulations assumed the cylinders to be rigid . In the present article, an approach is outlined to include deformation of the cylindrical particles in the numerical procedure.…”

“…As we will see, our existing computational framework for particle‐resolved simulations of dense suspensions involving nonspherical rigid particles, is well suited for an extension toward particle deformation. Given that in our methodology no‐slip conditions at particle surfaces are imposed through a forcing variant of the immersed boundary method (IBM), the distribution of forces over the solid surfaces is directly available in the simulation.…”

“…The aim of this article is to introduce and explain in detail an extension of previous work on particle‐resolved simulations of cylinder suspensions toward particles with finite bending stiffness with the deformed particle shape fully accounted for by the IBM. We also aim for demonstrating the potential of the method for applications with complex flow conditions by showing results for dense suspension of hundreds of flexible cylinders in a nontrivial—albeit laminar—liquid flow generated by a revolving impeller.…”