Simple Mechanistically Consistent Formulation for Volume-of-Fluid Based Computations of Condensing Flows

2014 ◽  
Vol 136 (7) ◽  
Author(s):  
Alexander S. Rattner ◽  
Srinivas Garimella
Keyword(s):  
Phase Change ◽  
Computational Cost ◽  
Volume Of Fluid ◽  
Film Condensation ◽  
Change Models ◽  
Software Complexity ◽  
Interface Reconstruction ◽  
Mesh Resolution ◽  
Condensing Flows ◽  
Gas Volume

Numerous investigations have been conducted to extend adiabatic liquid–gas volume-of-fluid (VOF) flow solvers to include condensation phenomena by adding an energy equation and phase-change source terms. Some proposed phase-change models employ empirical rate parameters, or adapt heat-transfer correlations, and thus must be tuned for specific applications. Generally applicable models have also been developed that rigorously resolve the phase-change process, but require interface reconstruction, significantly increasing computational cost, and software complexity. In the present work, a simplified first-principles-based condensation model is developed, which forces interface-containing mesh cells to the equilibrium state. The operation on cells instead of complex interface surfaces enables the use of fast graph algorithms without reconstruction. The model is validated for horizontal film condensation, and converges to exact solutions with increasing mesh resolution. Agreement with established results is demonstrated for smooth and wavy falling-film condensation.

Simple Mechanistically Consistent Formulation for Volume-of-Fluid Based Computations of Condensing Flows

2013 ◽  
Author(s):  
Alexander S. Rattner ◽  
Srinivas Garimella
Keyword(s):  
Phase Change ◽  
Computational Cost ◽  
Film Condensation ◽  
Falling Film ◽  
Change Models ◽  
Software Complexity ◽  
Interface Reconstruction ◽  
Mesh Resolution ◽  
Condensing Flows ◽  
Consistent Formulation

Numerous investigations have been conducted to extend adiabatic liquid-gas VOF flow solvers to include condensation phenomena by adding an energy equation and phase-change source terms. Some proposed phase-change models employ empirical rate parameters, or adapt heat transfer correlations, and thus must be tuned for specific applications. Generally applicable models have also been developed that rigorously resolve the phase-change process, but require interface reconstruction, significantly increasing computational cost and software complexity. In the present work, a simplified first-principles-based condensation model is developed, which forces interface-containing mesh cells to the equilibrium state. The operation on cells instead of complex interface surfaces enables the use of fast graph algorithms without reconstruction. The model is validated for horizontal film condensation, and converges to exact solutions with increasing mesh resolution. Agreement with established results is demonstrated for smooth and wavy falling-film condensation.

scholarly journals Numerical Study on an Interface Compression Method for the Volume of Fluid Approach

Fluids ◽  
2021 ◽  
Vol 6 (2) ◽  
pp. 80
Author(s):  
Yuria Okagaki ◽  
Taisuke Yonomoto ◽  
Masahiro Ishigaki ◽  
Yoshiyasu Hirose
Keyword(s):  
Linear Theory ◽  
Volume Fraction ◽  
Numerical Study ◽  
Volume Of Fluid ◽  
Interfacial Wave ◽  
Validation Process ◽  
Two Phase ◽  
Numerical Diffusion ◽  
Mesh Resolution ◽  
Water Reactors

Many thermohydraulic issues about the safety of light water reactors are related to complicated two-phase flow phenomena. In these phenomena, computational fluid dynamics (CFD) analysis using the volume of fluid (VOF) method causes numerical diffusion generated by the first-order upwind scheme used in the convection term of the volume fraction equation. Thus, in this study, we focused on an interface compression (IC) method for such a VOF approach; this technique prevents numerical diffusion issues and maintains boundedness and conservation with negative diffusion. First, on a sufficiently high mesh resolution and without the IC method, the validation process was considered by comparing the amplitude growth of the interfacial wave between a two-dimensional gas sheet and a quiescent liquid using the linear theory. The disturbance growth rates were consistent with the linear theory, and the validation process was considered appropriate. Then, this validation process confirmed the effects of the IC method on numerical diffusion, and we derived the optimum value of the IC coefficient, which is the parameter that controls the numerical diffusion.

Shock–like structure of phase-change flow in porous media

1981 ◽  
Vol 104 ◽  
pp. 467-482 ◽  
Author(s):  
L. A. Romero ◽  
R. H. Nilson
Keyword(s):  
Porous Media ◽  
Phase Change ◽  
Single Phase ◽  
Flow In Porous Media ◽  
Two Phase ◽  
Flows In Porous Media ◽  
Dissipative Effects ◽  
Condensing Flows ◽  
Self Similar ◽  
Phase Change Flows

Shock-like features of phase-change flows in porous media are explained, based on the generalized Darcy model. The flow field consists of two-phase zones of parabolic/hyperbolic type as well as adjacent or imbedded single-phase zones of either parabolic (superheated, compressible vapour) or elliptic (subcooled, incompressible liquid) type. Within the two-phase zones or at the two-phase/single-phase interfaces, there may be steep gradients in saturation and temperature approaching shock-like behaviour when the dissipative effects of capillarity and heat-conduction are negligible. Illustrative of these shocked, multizone flow-structures are the transient condensing flows in porous media, for which a self-similar, shock-preserving (Rankine–Hugoniot) analysis is presented.

Coupled Electro-Thermal-Phase Change Modeling of a Chalcogenide Switch

2006 ◽  
Author(s):  
Navdeep Singh Dhillon ◽  
Jayathi Y. Murthy
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Charge Transport ◽  
Crystallization Kinetics ◽  
Change Models ◽  
Switching Model ◽  
Memory Switching ◽  
Continuity Equations ◽  
Thermal Phase ◽  
Fully Coupled

A coupled electro-thermal-phase change numerical model is developed to model the threshold and memory switching processes in a chalcogenide switch based on phase change memory (PCM) technology. Coupled electrical and thermal transport coupled to phase change and crystallization kinetics are solved. Charge transport has been implemented using simplified carrier continuity equations with a threshold switching model for electrical conductivity. Heat transfer is modeled using a Fourier model, accounting for latent heat through a fixed-grid enthalpy formulation. Phase change is modeled using the Johnson-Mehl equations for crystallization kinetics. Thermal conductivity and electrical resistivity changes due to phase change are modeled using a local percolation model. The charge transport and circuit equations are fully coupled with the heat transfer and phase change models to accurately simulate the switching process. SET and RESET pulses are simulated to demonstrate that the model is able to capture the underlying physics well.

Numerical Simulation of Immersion Quench Cooling Process: Part I

2008 ◽  
Author(s):  
Vedanth Srinivasan ◽  
Kil-min Moon ◽  
David Greif ◽  
DeMing Wang ◽  
Myung-hwan Kim
Keyword(s):  
Phase Change ◽  
Nucleate Boiling ◽  
Vapor Flow ◽  
Cooling Process ◽  
Change Models ◽  
Liquid Domain ◽  
Commercial Code ◽  
Quenching Process ◽  
Solid Part ◽  
Quench Cooling

In this article, we describe a newly developed modeling procedure to simulate the immersion quench cooling process using the commercial code AVL-FIRE. The boiling phase change process, triggered by the dipping hot solid part into a subcooled liquid bath and the ensuing two-phase flow is handled using an Eulerian two-fluid method. Mass transfer effects are modeled based on different boiling modes such as film or nucleate boiling regime prevalent in the system. Separate computational domains constructed for the quenched solid part and the liquid (quenchant) domain are numerically coupled at the interface of the solid-liquid boundaries using the AVL-Code-Coupling-Interface (ACCI) feature. The advanced ACCI procedure allows the information pertaining to the phase change rates in the liquid domain to appear as cooling rates on the quenched solid boundaries. As a consequence, the code handles the multiphase flow dynamics in the liquid domain in conjunction with the temperature evolution in the solid region in a tightly coupled fashion. The methodology, implemented in the commercial code AVL-FIRE, is exercised in simulating the quenching of solid parts. In part I of the present research, phase change models are validated by simulating a work piece quenching process for which measurement data are available for various water temperature ranging from 20C to 80C. The computations provide a detailed description of the vapor and temperature fields in the liquid and solid domain at various time instants. In particular, the modifications arising in the liquid-vapor flow field in the near vicinity of the solid interface as a function of the boiling mode is well accommodated. The temperature history predicted by our model at different monitoring points, under different subcooling conditions, correlate very well with the experimental data wherever available. In part II, the model is further applied to real engine cylinder head quenching process and assessment is made for the cooling curves for various measuring points. Overall, the predictive capability of the new quenching model is well demonstrated.

Interfaces in Higher Order Phase Change Models

1984 ◽  
Vol 111 (1-2) ◽  
pp. 45-56
Author(s):  
P. Delano Hagan-Von Dreele ◽  
P. H. Von Dreele
Keyword(s):  
Phase Change ◽  
Higher Order ◽  
Change Models

scholarly journals 3-D numerical modelling of crustal polydiapirs with volume-of-fluid methods

2020 ◽  
Vol 222 (1) ◽  
pp. 474-506
Author(s):  
Aurélie Louis-Napoléon ◽  
Muriel Gerbault ◽  
Thomas Bonometti ◽  
Cédric Thieulot ◽  
Roland Martin ◽  
...  
Keyword(s):  
Volume Of Fluid ◽  
Vof Method ◽  
Earth’S Crust ◽  
Gravitational Instabilities ◽  
Interface Reconstruction ◽  
Rayleigh Taylor Instability ◽  
Earth's Crust ◽  
Two Stages ◽  
Rayleigh Benard ◽  
Earth Dynamics

SUMMARY Gravitational instabilities exert a crucial role on the Earth dynamics and in particular on its differentiation. The Earth’s crust can be considered as a multilayered fluid with different densities and viscosities, which may become unstable in particular with variations in temperature. With the specific aim to quantify crustal scale polydiapiric instabilities, we test here two codes, JADIM and OpenFOAM, which use a volume-of-fluid (VOF) method without interface reconstruction, and compare them with the geodynamics community code ASPECT, which uses a tracking algorithm based on compositional fields. The VOF method is well-known to preserve strongly deforming interfaces. Both JADIM and OpenFOAM are first tested against documented two and three-layer Rayleigh–Taylor instability configurations in 2-D and 3-D. 2-D and 3-D results show diapiric growth rates that fit the analytical theory and are found to be slightly more accurate than those obtained with ASPECT. We subsequently compare the results from VOF simulations with previously published Rayleigh–Bénard analogue and numerical experiments. We show that the VOF method is a robust method adapted to the study of diapirism and convection in the Earth’s crust, although it is not computationally as fast as ASPECT. OpenFOAM is found to run faster than, and conserve mass as well as JADIM. Finally, we provide a preliminary application to the polydiapiric dynamics of the orogenic crust of Naxos Island (Greece) at about 16 Myr, and propose a two-stages scenario of convection and diapirism. The timing and dimensions of the modelled gravitational instabilities not only corroborate previous estimates of timing and dimensions associated to the dynamics of this hot crustal domain, but also bring preliminary insight on its rheological and tectonic contexts.

scholarly journals Efficient and Accurate 3-D Numerical Modelling of Landslide Tsunami

Water ◽  
2019 ◽  
Vol 11 (10) ◽  
pp. 2033 ◽  
Author(s):  
Guodong Li ◽  
Guoding Chen ◽  
Pengfeng Li ◽  
Haixiao Jing
Keyword(s):  
Numerical Model ◽  
Mesh Generation ◽  
Water Waves ◽  
High Speed ◽  
Stokes Equations ◽  
Computational Cost ◽  
Similarity Criterion ◽  
Numerical Results ◽  
Mesh Resolution ◽  
Landslide Tsunami

High-speed and accurate simulations of landslide-generated tsunamis are of great importance for the understanding of generation and propagation of water waves and for prediction of these natural disasters. A three-dimensional numerical model, based on Reynolds-averaged Navier–Stokes equations, is developed to simulate the landslide-generated tsunami. Available experiment data is used to validate the numerical model and to investigate the scale effect of numerical model according to the Froude similarity criterion. Based on grid convergence index (GCI) analysis, fourteen cases are arranged to study the sensitivity of numerical results to mesh resolution. Results show that numerical results are more sensitive to mesh resolution in near field than that in the propagation field. Nonuniform meshes can be used to balance the computational efficiency and accuracy. A mesh generation strategy is proposed and validated, achieving an accurate prediction and nearly 22 times reduction of computational cost. Further, this strategy of mesh generation is applied to simulate the Laxiwa Reservoir landslide tsunami. The results of this study provide an important guide for the establishment of a numerical model of the real-world problem of landslide tsunami.

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