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.

A sharp surface tension modeling method for two‐phase incompressible interfacial flows

Abstract: A surface tension implementation algorithm for two-phase incompressible interfacial flows is presented in this study. The surface tension effect is treated as a jump condition at the interface and incorporated into the Navier-Stokes equation via a capillary pressure gradient. The interface is tracked by a coupled level set and volume-of-fluid (CLSVOF) method based on the finite-volume formulation on a fixed Eulerian grid. It has been shown in a stationary benchmark test the spurious currents are greatly reduced and the sharp pressure jump across the interface is well preserved. Numerical instabilities caused by the sharp treatment on a fixed grid are avoided. Several dynamic tests are performed to further validate the accuracy and versatility of the present method, the results of which are in good agreement with data reported in the literature.

Large eddy simulation of cavitating and non-cavitating flow

Abstract: Most marine configurations are subject to a number of complex and important hydrodynamic phenomena affecting the overall performance of the vessel, both regarding resistance and propulsive efficiency. In this thesis, the possibility of numerically simulating some of these phenomena is investigated. Due to the very wide range of flow scales present, i.e. the Reynolds (Re) number is high, in most marine applications, turbulence becomes an important factor. Another important issue, especially regarding propulsion, is cavitation. Cavitation occurs because the pressure in the flow is lowered below the vapour pressure and the liquid starts to boil. To be able to numerically predict these phenomena, using techniques that can be useful for the industry within a reasonable time frame, advanced physical modelling is needed. The models used in this thesis are incorporated in the incompressible Navier-Stokes equations (NSE) that forms the basic formulas for naval hydrodynamics. In principle, these equations can be solved for all scales in a Direct Numerical Simulation, but because of the high computational cost of for this technique, it will not be of use for industrial applications within a foreseeable future, instead a model for the turbulent scales is used. In this thesis a number of methodologies are investigated, with the main focus on Large Eddy Simulation (LES), but also using Reynolds Averaged Navier Stokes (RANS) and Detached Eddy Simulation (DES). These three methodologies, and subsets of them, are tested and validated on a number of configurations that are of interest for marine applications. The cases considered are the circular cylinder, the axisymmetric hill, a generic submarine hull, the Darpa Suboff configuration AFF1 and AFF8 and a number of hydrofoils in cavitating flow conditions. For the cavitating flow the same methodologies are used as in the single phase flow condition, but with the difference that the phase interface and the mass transfer from one phase to the other needs to be treated. The phase interface is taken care of using a Volume of Fluid (VOF) approach, where the interface is tracked using a volume fraction equation. The mass transfer process needs to be modelled since it occurs at length scales that are not supported by the continuum assumption, on which the NSE is based. The mass transfer models are incorporated in the NSE as source terms in the continuity equation and the volume fraction equation. The overall results of the simulations are very encouraging, including many physical phenomena that also can be seen in experiments. The results from the different methodologies and models are discussed, and possibilities and advantages are related. The main conclusion of the work is that LES will be a very useful tool for marine applications, especially for transient phenomena such as cavitation.

Effect of Nozzle Port Angle on Transient Flow and Surface Slag Behavior During Continuous Steel-Slab Casting

Abstract: Undesirable flow variations can cause severe instabilities at the interface between liquid mold flux and molten steel across the mold top-region during continuous steel casting, resulting in surface defects in the final products. A three-dimensional Large Eddy Simulation (LES) model using the volume of fluid method for the slag and molten steel phases is validated with plant measurements, and applied to gain new insights into the effects of nozzle port angle on transient flow, top slag/steel interface movement, and slag behavior during continuous slab casting under nominally steady conditions. Upward-angled ports produce a single-roll flow pattern with lower surface velocity, due to rapid momentum dissipation of the spreading jet. However, strong jet wobbling from the port leads to greater interface variations. Severe level drops allow easy entrapment of liquid flux by the solidifying steel shell at the meniscus. Sudden level rises may also be detrimental, leading to overflow of the solidified meniscus region. Downward-angled ports produce a classic double-roll pattern with less jet turbulence and a more stable interface everywhere except near the narrow faces. Finally, the flow patterns, surface velocity, and level predicted from the validated LES model are compared with steady-state standard k-e model predictions.