Lattice Boltzmann Model For Fluids Research Articles

Immiscible multicomponent lattice Boltzmann model for fluids with high relaxation time ratio

An immiscible multicomponent lattice Boltzmann model is developed for fluids with high relaxation time ratios, which is based on the model proposed by Shan and Chen (SC). In the SC model, an interaction potential between particles is incorporated into the discrete lattice Boltzmann equation through the equilibrium velocity. Compared to the SC model, external forces in our model are discretized directly into the discrete lattice Boltzmann equation, as proposed by Guo et al. We develop it into a new multicomponent lattice Boltzmann (LB) model which has the ability to simulate immiscible multicomponent fluids with relaxation time ratio as large as 29.0 and to reduce ‘spurious velocity’. In this work, the improved model is validated and studied using the central bubble case and the rising bubble case. It finds good applications in both static and dynamic cases for multicomponent simulations with different relaxation time ratios.

Simulation of Drug-Loaded Nanoparticles Transport Through Drug Delivery Microchannels

Ocular drug delivery is a complex and challenging process and understanding the transport characteristics of drug-loaded particles is very important for designing safe and effective ocular drug delivery devices. In this paper, we investigated the effect of the microchannel configuration of the microdevice, the size of drug-loaded nanoparticles (NPs), and the pressure gradient of fluid flow in determining the maximum number of NPs within a certain outlet region and transportation time of drug particles. We employed a hybrid computational approach that combines the lattice Boltzmann model for fluids with the Brownian dynamics model for NPs transport. This hybrid approach allows to capture the interactions among the fluids, NPs, and barriers of microchannels. Our results showed that increasing the pressure gradient of fluid flow in a specific type of microchannel configuration (tournament configuration) effectively decreased the maximum number of NPs within a certain outlet region as well as transportation time of the drug loaded NPs. These results have important implications for the design of ocular drug delivery devices. These findings may be particularly helpful in developing design and transport optimization guidelines related to creating novel microchannel configurations for ocular drug delivery devices.

Multicomponent interparticle-potential lattice Boltzmann model for fluids with large viscosity ratios

This work focuses on an improved multicomponent interparticle-potential lattice Boltzmann model. The model results in viscosity-independent equilibrium densities and is capable of simulating kinematic viscosity ratios greater than 1000. External forces are incorporated into the discrete Boltzmann equation, rather than through an equilibrium velocity shift as in the original Shan and Chen (hereafter, SC) model. The model also requires the derivation of a momentum conserving effective velocity, which is substituted into the equilibrium distribution function and applies to both the single- and multiple-relaxation-time formulations. Additionally, higher-order isotropy is used in the calculation of the fluid-fluid interaction forces to reduce the magnitude of spurious currents (i.e., numerical errors) in the vicinity of interfaces. First, we compare the model to the SC model for static bubble simulations. We demonstrate that the model results in viscosity-independent equilibrium bubble densities for a wide range of kinematic viscosities, which is not the case for the SC model. Furthermore, we show that the model is capable of simulating stable bubbles for kinematic viscosity ratios greater than 1000 (when higher-order isotropy is used), whereas the SC model is known to be limited to kinematic viscosity ratios on the order of 10. Next we verify the model for surface tension via Laplace's law and show that the model results in the same surface tension values for a range of kinematic viscosities and kinematic viscosity ratios of 10, 100, and 1000. The model is also verified for layered cocurrent flow though parallel plates. We show that the simulated velocity profiles preserve continuity at the interface for kinematic viscosity ratios ranging from 0.001 to 1000 and that the model accurately predicts nonwetting and wetting phase relative permeability for kinematic viscosity ratios of 0.01 to 100.