Volume of fluid method

About: Volume of fluid method is a research topic. Over the lifetime, 5338 publications have been published within this topic receiving 116760 citations.

Computational analysis of self-similar capillary-driven thinning and pinch-off dynamics during dripping using the volume-of-fluid method

Abstract: Drop formation and detachment involve large topological changes, including the formation of a fluid neck that thins down due to surface tension-driven flows, and at the neck pinch-off, properties like Laplace pressure display a finite time singularity. Accurately simulating large topological deformations and nonlinearities encountered during drop formation typically makes numerical simulations computationally demanding as resolving small features close to the pinch-off instant requires high resolution and accuracy. In spite of the inherent advantages in tracking interfaces, preserving mass and computational time needed, very few studies utilize the volume-of-fluid (VOF) method for drop formation studies as early practitioners reported convergence problems for fluids with viscosity greater than ten times water viscosity. In this contribution, we utilize the VOF method as implemented in FLOW-3D to simulate the prototypical free surface flow of dripping for Newtonian fluids, including viscosity values four orders of magnitude higher than water viscosity. We benchmark the simulated neck shape, neck evolution rate, and break-up length against experiments carried out as a part of this study. The pinch-off dynamics are determined by a complex interplay of inertial, viscous, and capillary stresses, and self-similar scaling laws that are contrasted here against both experiments and simulations often describe the dynamics. We show that the simulated radius evolution profiles match the pinch-off dynamics that are experimentally observed and theoretically predicted for Newtonian fluids for axisymmetric flows. Furthermore, we determine pre-factors for scaling laws, velocity, and deformation fields within thinning necks, and we show that pre-factors, as well as break-up time and length comparable to experiments can be simulated using the VOF method.

DebrisInterMixing-2.3: a finite volume solver for three-dimensional debris-flow simulations with two calibration parameters – part 1: model description

Abstract: . Here, we present a three-dimensional fluid dynamic solver that simulates debris flows as a mixture of two fluids (a Coulomb viscoplastic model of the gravel mixed with a Herschel–Bulkley representation of the fine material suspension) in combination with an additional unmixed phase representing the air and the free surface. We link all rheological parameters to the material composition, i.e., to water content, clay content, and mineral composition, content of sand and gravel, and the gravel's friction angle; the user must specify only two free model parameters. The volume-of-fluid (VoF) approach is used to combine the mixed phase and the air phase into a single cell-averaged Navier–Stokes equation for incompressible flow, based on code adapted from standard solvers of the open-source CFD software OpenFOAM. This effectively single-phase mixture VoF method saves computational costs compared to the more sophisticated drag-force-based multiphase models. Thus, complex three-dimensional flow structures can be simulated while accounting for the pressure- and shear-rate-dependent rheology.

A New Volume-Of-Fluid Method in Openfoam

Abstract: To realise the full potential of Computational Fluid Dynamics (CFD) within marine science and engineering, there is a need for continuous maturing as well as verification and validation of the numerical methods used for free surface and interfacial flows. One of the distinguishing features here is the existence of a water surface undergoing large deformations and topological changes during transient simulations e.g. of a breaking wave hitting an offshore structure. To date, the most successful method for advecting the water surface in marine applications is the Volume-of-Fluid (VOF) method. While VOF methods have become quite advanced and accurate on structured meshes, there is still room for improvement when it comes to unstructured meshes of the type needed to simulate flows in and around complex geometric structures. We have recently developed a new geometric VOF algorithm called isoAdvector for general meshes and implemented it in the OpenFOAM interfacial flow solver called interFoam. We have previously shown the advantages of isoAdvector for simple pure advection test cases on various mesh types. Here we test the effect of replacing the existing interface advection method in interFoam, based on MULES limited interface compression, with the new isoAdvector method. Our test case is a steady 2D stream function wave propagating in a periodic domain. Based on a series of simulations with different numerical settings, we conclude that the introduction of isoAdvector has a significant effect on wave propagation with interFoam. There are several criteria of success: Preservation of water volume, of interface sharpness and shape, of crest kinematics and celerity, not to mention computational efficiency. We demonstrate how isoAdvector can improve on many of these parameters, but also that the success depends on the solver setup. Thus, we cautiously conclude that isoAdvector is a viable alternative to MULES when set up correctly, especially when interface sharpness, interface smoothness and calculation times are important. There is, however, still potential for improvement in the coupling of isoAdvector with interFoam’s PISO based pressure-velocity solution algorithm.