Coupling of finite-volume-method and incompressible smoothed particle hydrodynamics method for multiphase flow

It is an intuitive way to use the advantages of two different simulation methods, such as the Finite-Volume (FV) and Smoothed Particle Hydrodynamics (SPH), to reduce the computational effort. Finite-Volume, like other grid-based methods, is advan- tageous for huge systems without fluid-fluid interfaces, whereas SPH is advantageous in the vicinity of fluid interfaces. We will present our first results for a combined simula- tion, including a moving SPH domain, in a simple Poiseuille flow and a more complex multiphase capillary rise scenario

High Weissenberg number simulations with incompressible Smoothed Particle Hydrodynamics and the log-conformation formulation

Viscoelastic flows occur widely, and numerical simulations of them are important for a range of industrial applications. Simulations of viscoelastic flows are more challenging than their Newtonian counterparts due to the presence of exponential gradients in polymeric stress fields, which can lead to catastrophic instabilities if not carefully handled. A key development to overcome this issue is the log-conformation formulation, which has been applied to a range of numerical methods, but not previously applied to Smoothed Particle Hydrodynamics (SPH). Here we present a 2D incompressible SPH algorithm for viscoelastic flows which, for the first time, incorporates a log-conformation formulation with an elasto-viscous stress splitting (EVSS) technique. The resulting scheme enables simulations of flows at high Weissenberg numbers (accurate up to Wi=85 for Poiseuille flow). The method is robust, and able to handle both internal and free-surface flows, and a range of linear and non-linear constitutive models. Several test cases are considerd included flow past a periodic array of cylinders and jet buckling. This presents a significant step change in capabilties compared to previous SPH algorithms for viscoelastic flows, and has the potential to simulate a wide range of new and challenging applications.Comment: submitted to JNNFM Sept. 2020, revised March 202

Prediction of Electrolyte Distribution in Technical Gas Diffusion Electrodes From Imaging to SPH Simulations

The performance of the gas diffusion electrode GDE is crucial for technical processes like chlorine alkali electrolysis. The function of the GDE is to provide an intimate contact between gaseous reactants, the solid catalyst, and the liquid electrolyte. To accomplish this, the GDE is composed of wetting and non wetting materials to avoid electrolyte breakthrough. Knowledge of the spatial distribution of the electrolyte in the porous structure is a prerequisite for further improvement of GDE. Therefore, the ability of the electrolyte to imbibe into the porous electrode is studied by direct numeric simulations in a reconstructed porous electrode. The information on the geometry, including the information on silver and PTFE distribution of the technical GDE, is extracted from FIB SEM imaging including a segmentation into the different phases. Modeling of wetting phenomena inside the GDE is challenging, since surface tension and wetting of the electrolyte on silver and PTFE surfaces must be included in a physically consistent manner. Recently, wetting was modeled from first principles on the continuum scale by introducing a contact line force. Here, the newly developed contact line force model is employed to simulate two phase flow in the solid microstructures using the smoothed particle hydrodynamics SPH method. In this contribution, we present the complete workflow from imaging of the GDE to dynamic SPH simulations of the electrolyte intrusion process. The simulations are used to investigate the influence of addition of non wetting PTFE as well as the application of external pressure differences between the electrolyte and the gas phase on the intrusion proces

Free Liquid Drag−out from a Liquid Bath Using SPH

The liquid drag−out (LDO) coating process is a key process in metallic−coated strip production in continuous galvanising lines. The liquid is dragged−out by the strip when the strip pulls up from a bath. The liquid in the process is commonly liquid zinc. The LDO physical understanding is important to control the liquid film thickness, coated strip smoothness and production efficiency. The thesis aimed to understand free LDO fundamentals by developing a numerical tool to simulate the free LDO process. The LDO fundamentals (meniscus, stagnation point, re-circulation flow, boundary layer thickness) analysis are important, as the film is influenced by the fundamentals. A graphical processing unit (GPU) enables a Smoothed Particle Hydrodynamics (SPH) tool is to be developed using MATLAB. The SPH tool is validated against the numerical cases: lid−driven cavity, a hydrostatic tank under gravity and a droplet spreading on a solid surface. The inter−particle interaction (IIF) technique is used in modelling the surface tension and adhesion. Non−periodic inlet and outlet boundaries are present in LDO problem. Mirror buffer technique with SPH is implemented in the outlet to model the gradient−free Neumann boundary. Also, to conserve the domain mass over time, a novel approach is introduced to return the domain leaving particle immediately to the domain at the next time step