Lattice-Boltzmann Simulation and Experimental Validation of a Microfluidic T-Junction for Slug Flow Generation

Abstract

We investigate the interaction of two immiscible fluids in a head-on device geometry, where both fluids are streaming opposite to each other. The simulations are based on the two-dimensional (2D) lattice Boltzmann method (LBM) using the Rothman and Keller (RK) model. We validate the LBM code with several benchmarks such as the bubble test, static contact angle, and layered flow. For the first time, we simulate a head-on device by forcing periodicity and a volume force to induce the flow. From low to high flow rates, three main flow patterns are observed in the head-on device, which are dripping-squeezing, jetting-shearing, and threading. In the squeezing regime, the flow is steady and the droplets are equal. The jetting-shearing flow is not as stable as dripping-squeezing. Moreover, the formation of droplets is shifted downstream into the main channel. The last flow form is threading, in which the immiscible fluids flow parallel downstream to the outlet. In contrast to other studies, we select larger microfluidic channels with 1-mm channel width to achieve relatively high volumetric fluxes as used in chemical synthesis reactors. Consequently, the capillary number of the flow regimes is smaller than 10−5. In conclusion, the simulation compares well to experimental data.

Directional Water Wicking on a Metal Surface Patterned by Microchannels

“…Then, when the interface diffusion becomes large, we employ the color gradient Lattice Boltzmann Method (LBM). The equations of the LBM code is described in [46]. The relevance of each code depending on the simulation is discussed in Section 5.…”

“…We believe that the interface diffusion may underestimate the capillary force and then mislead the wicking dynamics simulation. The color gradient Lattice Boltzmann Method (LBM) used in [46] provides an alternative to model interface dynamics. The interface diffusion is drastically reduced by LBM simulation compared to VOF for a similar mesh refinement (Figure 18).…”

Numerical study of drop behavior in a pore space

“…The analytical solution for the velocity in the channel as a function of the wall normal coordinate Z was calculated from the Navier-Stokes equation (Schulz et al, 2019): is the pressure gradient, 2h is the channel height, y is the direction of the flow and and . are the dynamic viscosities of the liquids that have the same density (ρ 1 =ρ 2 =1.0 lu).…”

Geometrically driven liquid wicking: numerical study and experimental validation

“…The color gradient Lattice Boltzmann Method (LBM) described in [16] restricts interface diffusion, and does not exhibit the right front pinning observed in the VOF simulation: the right front still stops at the same sharp corner at fins entrance. However, a small amount of water is observed in the tip of the fin.…”