In this work a numerical method for fully three dimensional simulations of a capsule in the electrohydrodynamic regime is proposed. A quasi-steady dual time-stepping scheme allows for iterative computation of the capsule’s fluid velocity using the multigrid lattice Boltzmann method at each time step. The capsule’s elasticity is computed using a linear finite element method and the membrane’s bending resistance is computed from the Helfrich bending energy. The immersed interface method (IIM) is used to compute the electric field arising due to the electrical properties of the interior fluid, exterior fluid, and the membrane. The fluid structure interaction is facilitated through the immersed boundary method (IBM), which is coupled to the IIM through least squares interpolation between the control points of the IIM and the Lagrangian nodes of the IBM. The method is validated by comparing the numerical results to analytical solutions and previously published studies. The method is then used to study the deformation of a capsule in a combined shear flow and DC electric field for various membrane conductances, membrane capacitances, and conductivity ratios. For nonconducting membranes the interaction between the distribution of the electric forces and the capsule inclination angle due to the shear flow result in complex equilibrium dynamics not reported for neutral capsules.

One sometimes wants to run lattice Boltzmann simulations with more precision than is available in commonly supported floating point arithmetic. This is particularly true for confirming qualitative properties such as conservation laws. It is also true for GPUs where one may be restricted to 32b-bit floating point numbers. This talk presents a rescaling of the Skordos (1993) variable transformation to formulate a lattice Boltzmann scheme that can be implemented using integer arithmetic. In particular, 128-bit integer arithmetic is efficient on common hardware such as x86-64. Standard lattice Boltzmann schemes require division, while variants that target the Chorin artificial compressibility equations do not. The extra division comes at significant computational cost, even in floating point arithmetic, and is implemented using Newton's method in integer arithmetic.

Sharp and diffuse interface models are usually considered to be two fundamentally different approaches to the modeling of multiphase flows. In this contribution we discuss a conservative lattice Boltzmann phase field model as a phase separator and a momentum balance boundary condition forming a sharp interface. In this approach, the interaction between the two phases is limited to the nodes directly adjacent to the interface. This allows us to directly apply the super convergent cumulant lattice Boltzmann method in both domains and benefit from its excellent stability properties.

A convergence study of LB diffusion-interface method

The simulation of fluid flow around wind turbines is key to improve the performance and reliability of wind turbines in varying wind conditions. To quantify the impact of complex wind patterns on wind turbine components, high-fidelity simulations are essential. Thus, we investigate a method for simulating wind dynamics induced by a three-blade turbine with the Lattice Boltzmann Method (LBM) implemented for GPUs. Our approach uses a rotating overset lattice, where the wind turbine rotor is embedded in a lattice that rotates synchronously with the rotor. The rotating lattice is coupled with a static lattice that represents the surrounding fluid domain. An efficient and accurate interpolation technique for the coupling of the lattices is pivotal for this approach. We use a compact quadratic interpolation technique tailored to the cumulant LBM. The interpolation process involves rotating the distributions by manipulating their moments, while also accounting for Coriolis and centrifugal forces on the rotating mesh. In addition, the compact quadratic interpolation is optimized for massively parallel execution on a graphics processing unit (GPU) to reduce simulation times. This improves the scalability of our approach and provides a promising solution for advancing high-fidelity simulations of rotating objects.

The modelling of fluid-filled vesicles \textemdash such as red blood cells (RBCs) \textemdash has obvious importance in the field of biomedical science. Given a healthy human RBC has dimensions of approximately 8$\mu$m in length and 2$\mu$m in width, the modelling of RBCs often utilises mesoscale modelling approaches such as single-component lattice Boltzmann method (SCLBM).

Presented here is an alternative approach to simulating vesicles in three-dimensions using chromodynamic multi-component lattice Boltzmann method (cMCLBM).

By capitalising on the natural disparity in length scales—typified by the RBC membrane's width of approximately 40nm—and operating within the continuum approximation of fluids, the RBC's interior is conceptualised as one immiscible fluid, its exterior as another, and the quasi-two-dimensional interface between them as the \textit{de-facto} membrane. The primary advantage of this approach lies in its unified methodology, requiring only the cMCLBM framework to model both fluids and the deformable body. This presentation outlines the model, showing: (i) the foundational methodology, (ii) two-component simulations (a single vesicle), and (iii) the expansion of the methodology to simulate multiple vesicles, with attention being drawn to the advantages of such an approach.

In the last decades, Micro-channels and micro-cavities becomes a subject of interest of many researchers due to their higher efficiency. The contemporary study aims to numerically analyze the convective heat transfer and entropy generation analysis for the case of a micro-channel filled with Cu/water under the effect of inclination angle in the slip flow regime. a series of numerical simulations based on the Lattice Boltzmann method are carried out in a micro medium filled with nanoliquid. To resolve the governing equations, a special treatment of boundary conditions precisely at the side walls is done. The obtained results are presented in terms of heat transfer rate and surface distribution of entropy generation.

Estimation of permeability of porous media dates back to Henry Darcy (1856). The literature data on permeability are scattered, and this scatter not always can be attributed to the accuracy of experiment or simulation or to the sample variability. In this work, we prepare porous samples and determine their permeability experimentally. Hereafter, the samples are scanned in 3D using X-ray computed tomography, and the images are used for Stokes flow simulations using the lattice Boltzmann method with the simple bounce-back boundary condition. Careful execution of all steps in this combined experiment-simulation study resulted in an excellent agreement (<1%) between laboratory results and simulations. Here, experimental results are extensive and stable, while flow is simulated directly on three-dimensional images and without fitting parameters. Analyzing the conditions when experiments and simulations agree reveals a flaw affecting many experimental measurements with the out-of-sample placement of pressure ports, including industry standards. The flaw originates from (1) incorrect calculation of the applied pressure gradient, (2) omitting virtual part of the measured system, and (3) pressure loss at the sample–tube contact. Contrary to common wisdom, the relative magnitude of (3) is defined by the sample–tube diameter ratio and is independent of the size of sample pores. Removing or taking the flaw into account advances the understanding and control of flow-related processes in complex geometries.