Showing papers on "Volume of fluid method published in 2020"
TL;DR: This work extensively verified and validated the overall method against several benchmark cases, and demonstrated its excellent mass conservation and good overall performance for simulating evaporating two-fluid flows in two and three dimensions.
51 citations
TL;DR: In this paper, the effects of the water velocity in the GDL hole, the airflow velocity and the wettability of the channel surfaces on the water emerging process and transport in the flow channel are investigated.
43 citations
TL;DR: In this article, a three-dimensional numerical model is established to study the mass transport and heat transfer in the melt pools in high deposition rate (HDR) L-DED of 316L stainless steel.
Abstract: In laser directed energy deposition (L-DED) processes, by applying a converged powder stream, relatively high laser power and larger laser spot, the powder utilisation efficiency and processing speed can be increased. There is, however, lack of mathematical models for L-DED. In this paper, a three-dimensional numerical model is established to study the mass transport and heat transfer in the melt pools in high deposition rate (HDR) L-DED of 316L stainless steel. The Volume of Fluid (VOF) method is employed to track the melt pool free surfaces, and enthalpy-porosity method is used to model the solid-liquid phase change. A discrete powder source model is developed by considering the non-uniform powder feed rate distribution. Results show that this model can well predict the deposited track dimensions (width, height and dilution depth). Different from conventional L-DED processes, the impact of higher mass addition on the melt pool fluid flow and temperature distribution is significant. In the regions where filler powder is injected, a downward mass flow is observed, and the temperature is slightly reduced. With the extracted temperature distribution and geometry at the solidification front, the solidification conditions are also calculated, as well as the primary dendrite arm spacing (PDAS) of the solidified tracks. Due to the high laser energy input, the temperature gradient is lower, and coarser microstructures are formed compared with conventional L-DED. The simulated results are in good agreement with experimental results.
42 citations
TL;DR: In this article, the authors proposed a discretely conservative and bounded phase field equation, which is free of any reinitialization or mass redistribution, possesses desirable properties that can be leveraged in the coupled finite difference discretization of the two-phase momentum equation.
39 citations
TL;DR: In this paper, the influence of the geometric parameters of trapezoidal-triangular labyrinth weirs on discharge coefficient, energy dissipation, and downstream flow regime, considering two different orientations in labyrinth weir position respective to the reservoir discharge channel.
Abstract: In this work experimental and numerical investigations were carried out to study the influence of the geometric parameters of trapezoidal–triangular labyrinth weirs (TTLW) on the discharge coefficient, energy dissipation, and downstream flow regime, considering two different orientations in labyrinth weir position respective to the reservoir discharge channel. To simulate the free flow surface, the volume of fluid (VOF) method, and the Renormalization Group (RNG) k-e model turbulence were adopted in the FLOW-3D software. The flow over the labyrinth weir (in both orientations) is simulated as a steady-state flow, and the discharge coefficient is validated with experimental data. The results highlighted that the numerical model shows proper coordination with experimental results and also the discharge coefficient decreases by decreasing the sidewall angle due to the collision of the falling jets for the high value of H/P (H: the hydraulic head, P: the weir height). Hydraulics of flow over TTLW has free flow conditions in low discharge and submerged flow conditions in high discharge. TTLW approximately dissipates the maximum amount of energy due to the collision of nappes in the upstream apexes and to the circulating flow in the pool generated behind the nappes; moreover, an increase in sidewall angle and weir height leads to reduced energy. The energy dissipation of TTLW is largest compared to vertical drop and has the least possible value of residual energy as flow increases.
39 citations
TL;DR: In this article, the authors numerically investigated the distribution characteristics of particles within liquid slugs (reactors) in a vertical capillary tube, with the aim to describe the corresponding underlying mechanisms.
35 citations
TL;DR: In this article, a three-phase flow model that captures the details of the gas layer thickness and dynamics of fluid motions was proposed to investigate the thickness of the entrapped air during the impact process while the behavior of droplet and immiscible liquid film was quantitatively measured.
34 citations
TL;DR: A novel unified single-field formulation for Volume-Of-Fluid simulation of interfacial mass transfer with local volume changes, shown to be well adapted to investigate Sherwood numbers and existing correlation for mass transfer at fluid interfaces.
34 citations
TL;DR: In this paper, a phenomenological model based on local temperature and superheat degree is proposed to predict the formation of vapor bubbles inside the water droplet. And the growth rate of the bubbles is computed with OCASIMAT phase-change algorithm.
33 citations
TL;DR: The relation among the insulation thickness and total heat leak is established, showing that the obtained increased heat ingress due to lower insulation thickness values leads to a rise in pressurization and boil-off rates.
32 citations
TL;DR: In this article, the authors examine the accuracy of common numerical models and explain the influence of installing an inducer or increasing the tip clearance gap on the performance of a centrifugal pump.
TL;DR: In this paper, the cavitation-vortex interaction is studied with the vorticity transport equation and much stronger baroclinic torque term is observed by the large eddy simulation (LES) method coupled with the volume of fluid (VOF) model in OpenFOAM.
TL;DR: In this article, a three-phase volume of fraction (VOF) model was built to analyze the movement and formation of the tea leaf paradox in a whirlpool, and the simulated shape of the cone was compared to its counterparts obtained under industrial conditions.
TL;DR: In this paper, the assessment of five phase change models (Lee model, temperature recovery model, phase field model, heat flux balance model, and empirical correlation model) on the simulation of bubble condensation was investigated using the volume of fluid (VOF) method.
TL;DR: In this paper, a one-way coupled fluid-structure framework was developed to explore the slug flow interaction with a horizontal pipe assembly under various superficial gas and liquid velocities.
TL;DR: An effective modeling framework using the large eddy simulation (LES) approach along with the volume of fluid (VOF) method to simulate the two-phase flow system and applies the Schnerr-Sauer model to calculate the mass-transfer rate between water and vapor is proposed.
Abstract: Cavitating flows are dominated by large gradients of physical properties and quantities containing complicated interfacial structures and lots of multi-scale eddies that need to be accurately characterized using a high-resolution mesh. The present work, within OpenFOAM, proposes an effective modeling framework using the large eddy simulation (LES) approach along with the volume of fluid (VOF) method to simulate the two-phase flow system and applies the Schnerr-Sauer model to calculate the mass-transfer rate between water and vapor. The adaptive mesh refinement (AMR) which is a powerful tool for allocating high-resolution grids only to the region of the greatest concern is adopted for improving the solution of interfacial structures. The effect of grid size is firstly investigated and the time-averaged quantities are verified against the experimental data, and then simulations of cavitating flows are successfully achieved to precisely characterize the features of cavitation with automatically and dynamically refining the mesh. As the refinement only takes place in the interfacial region, high-precision simulations can be achieved with limited computational resources, and the method shows promising prospects for modeling of the multi-scale, time-critical and computationally intensive cavitating flows.
TL;DR: In this article, a two-phase compressible flow model was established based on N-S equations and modeled by VOF (Volume of Fluid) algorithm, where geometric reconstruction approach was adopted to track the free surface and a dynamic mesh approach was used to treat body motion.
TL;DR: Numerical predictions from large-eddy simulations are compared against experimental results available from literature and validation against high-speed camera visualizations and Laser Doppler Velocimetry measurements of cavitating microscopic in-nozzle flows in a fuel injector is reported.
TL;DR: In this paper, a 3D conjugate numerical simulation of the diverging microchannel heat sink was performed using the volume of fluid (VOF) model coupled with the phase change model, which is used to analyze the flow boiling and transient heat transfer mechanism through simulation of bubble nucleation, bubble growth pattern, pressure, temperature, and vapor quality variations.
TL;DR: In this paper, the behavior of water drop in a flow behind incident shock wave and verification of calculations on this basis is devoted to experimental and computational studies of the water drop behavior.
TL;DR: In this article, the influence of the compressibility effect on the air inside the oscillating water column (OWC) chamber by the FLUENT® numerical model is investigated, taking into account both water and air flows incompressible, but, at every instant, a pressure condition is imposed on the top boundary of the chamber to consider the compressible effect.
TL;DR: This work presents several validation cases and shows, that the method implemented into the CFD code FS3D is able to simulate evaporation processes for a large range of ambient conditions, ranging from supercooled droplets to extreme environments with highevaporation rates.
TL;DR: In this article, a dam-break flow over a channel with a contracting reach was investigated experimentally and numerically, and the experimental results were compared against the numerical solution of VOF (Volume of Fluid)-based Shallow Water Equations (SWEs) and Reynolds-Averaged Navier-Stokes (RANS) equations with the k-e turbulence model.
Abstract: Dam-break wave propagation usually occurs over irregular topography, due for example to natural contraction-expansion of the river bed and to the presence of natural or artificial obstacles. Due to limited available dam-break real-case data, laboratory and numerical modeling studies are significant for understanding this type of complex flow problems. To contribute to the related field, a dam-break flow over a channel with a contracting reach was investigated experimentally and numerically. Laboratory tests were carried out in a smooth rectangular channel with a horizontal dry bed for three different lateral contraction geometries. A non-intrusive digital imaging technique was utilized to analyze the dam-break wave propagation. Free surface profiles and time variation of water levels in selected sections were obtained directly from three synchronized CCD video camera records through a virtual wave probe. The experimental results were compared against the numerical solution of VOF (Volume of Fluid)-based Shallow Water Equations (SWEs) and Reynolds-Averaged Navier-Stokes (RANS) equations with the k-e turbulence model. Good agreements were obtained between computed and measured results. However, the RANS solution shows a better correspondence with the experimental results compared with the SWEs one. The presented new experimental data can be used to validate numerical models for the simulation of dam-break flows over irregular topography.
TL;DR: In this paper, a computational modeling approach was used, and the sand erosion in gas-liquid-solid annular three-phase flows in pipe bends was analyzed, where the Volume of Fluid (VOF) and the hybrid Eulerian-Eulerian methods were used to simulate the 3D transient annular air-water flows.
TL;DR: In this paper, a closed pulsating heat pipe with a periodic expansion-constriction condenser was proposed, where phase change and thermal transport processes could be reproduced by a comprehensive computational fluid dynamics (CFD) technique together with volume of fluid (VOF) methodology.
TL;DR: In this article, the authors investigate and better understand two-phase flow characteristics in the annulus using computational fluid dynamics and experimental approaches, and compare their results with the experimental data within a mean error of 20%.
Abstract: Simulations of two-phase (air and water) flow in a pipe are among the widely discussed topics; however, with the increased understanding of multiphase flow in pipes, the application of computational fluid dynamics (CFD) in other complex flow geometries involved in oilfield operations is becoming more common. This study is aimed to investigate and better understand two-phase flow characteristics in the annulus using computational fluid dynamics and experimental approaches. The experimental study included two sets of five tests with increasing superficial gas velocity (9.2–47.2 m/s) at a constant liquid flow rate. Experiments were conducted in concentric annulus test Section (35 mm × 82.5 mm) that had an overall length of 5.5 m. Two flow patterns (churn and annular) were observed during the experiment. Using CFD simulation, pressure drop, void fraction, and flow regime are determined. The VOF multiphase model and two turbulence models (realizable k-e and SST k-ω models) were implemented, and comparative study was conducted to understand the relevance of each method in high gas velocity scenarios for flow in the annulus. The simulated macroscopic behavior of the flow shows consistent pressure gradient patterns and mimics the void fraction behavior. Probability density functions were implemented on time series evolution of void fraction to identify the flow regime for the CFD results. The simulation results show a reasonable agreement with the experimental data within a mean error of 20%.
TL;DR: In this paper, the formation of the cone-jet in the electrospray process is investigated with considering the space charge effects, and an improved model of considering the effect of charged droplet emitted from the tip of cone-joint on the external electric field is proposed.
TL;DR: The versatility and robustness of the present two-phase flow model is illustrated via various two- and three-dimensional flow problems with fixed/moving bodies, such as dambreak flows with and without a square cylinder, a moving cylinder in a quiescent fluid, dambreak flow over a wet bed with a moving gate, water entry and exist of a circular cylinder, and landside-generated waves.
TL;DR: A new auxiliary continuity equation is introduced and resolved along the momentum equations in the velocity control volumes to achieve a consistent mass-momentum advection, suitable to simulate more complex and realistic high density ratio two-phase flows, such as the breakup of a liquid jet in cross-flow here described.
TL;DR: In this article, a 3D computational approach was developed to predict highly subcooled nucleate flow boiling in vertical upflow, where the authors used a user defined function to provide detailed information relating to the shear lift force on bubbles.