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.

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.

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 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.

Empirical modelling of beach evolution: implementation of coupled cross-shore and longshore approaches

2020 ◽  
Author(s):  
Teddy Chataigner ◽  
Marissa Yates ◽  
Nicolas Le Dantec
Keyword(s):  
Morphological Evolution ◽  
Computational Cost ◽  
Sandy Beaches ◽  
Sediment Flux ◽  
Beach Profile ◽  
Change Models ◽  
Empirical Modelling ◽  
Spatial And Temporal Scales ◽  
Shoreline Evolution

<p>Understanding shoreline evolution, and in particular, the consequences of shoreline erosion is a<br>major societal concern that threatens to become even more important in the future with the impacts<br>of climate change. Thus, it is necessary to improve both knowledge of the dominant physical processes<br>controlling medium to long-term shoreline evolution and the capabilities of morphological evolution<br>models to simulate beach changes at these spatial and temporal scales.<br>Empirical models may be an ideal choice for modelling complex and dynamic environments such as<br>sandy beaches at large spatial (beach) and long temporal (years to decades) scales. They reproduce<br>the effects of the main morphodynamical processes with low computational cost and relatively high<br>accuracy, in particular when high quality, long-term data are available for calibration.<br>Here, to broaden its range of application, a cross-shore equilibrium model, which has demon-<br>strated its accuracy and efficiency in reproducing shoreline and intertidal beach profile changes at<br>several micro and macrotidal beaches, is extended to couple it with a longshore beach evolution<br>modelling approach. The selection of a particular longshore model (based on a one-line approach),<br>and its implementation and validation with benchmark test cases of shoreline evolution caused by<br>the effects of diffusion, high angle wave instabilities, and coastal structures are presented.<br>The new hybrid model is applied at Narrabeen beach to reproduce the long-term evolution of<br>beach contours near the shoreline. The model is calibrated and tested using the 40-year timeseries of<br>monthly subaerial beach profile surveys conducted along 5 cross-shore profiles along the 3.6km-long<br>Narrabeen-Collaroy embayment. The novelty of the current work is to focus on reproducing changes<br>at different altitudes, with the objective of assessing the cross-shore variability of the longshore<br>sediment flux, which is assumed constant in most one-line longshore transport models. The coupled<br>model performance is discussed, and the results are compared to existing studies that have simulated<br>shoreline evolution at Narrabeen using other morphological change models.</p>

scholarly journals Adaptive Mesh Optimization for Simulation of Immiscible Viscous Fingering

SPE Journal ◽  
2016 ◽  
Vol 21 (06) ◽  
pp. 2250-2259 ◽  
Author(s):  
Peyman Mostaghimi ◽  
Fatemeh Kamali ◽  
Matthew D. Jackson ◽  
Ann H. Muggeridge ◽  
Christopher C. Pain
Keyword(s):  
Finite Volume ◽  
Control Volume ◽  
Computational Cost ◽  
Adaptive Mesh ◽  
Viscous Fingering ◽  
Numerical Dispersion ◽  
Mesh Optimization ◽  
Mesh Adaptivity ◽  
Metric Tensor ◽  
Mesh Resolution

Summary Viscous fingering can be a major concern when waterflooding heavy-oil reservoirs. Most commercial reservoir simulators use low-order finite-volume/-difference methods on structured grids to resolve this phenomenon. However, this approach suffers from a significant numerical-dispersion error because of insufficient mesh resolution, which smears out some important features of the flow. We simulate immiscible incompressible two-phase displacements and propose the use of unstructured control-volume finite-element (CVFE) methods for capturing viscous fingering in porous media. Our approach uses anisotropic mesh adaptation where the mesh resolution is optimized on the basis of the evolving features of flow. The adaptive algorithm uses a metric tensor field dependent on solution-interpolation-error estimates to locally control the size and shape of elements in the metric. The mesh optimization generates an unstructured finer mesh in areas of the domain where flow properties change more quickly and a coarser mesh in other regions where properties do not vary so rapidly. We analyze the computational cost of mesh adaptivity on unstructured mesh and compare its results with those obtained by a commercial reservoir simulator on the basis of the finite-volume methods.

Falling Film Transitions on Plain and Enhanced Tubes

2002 ◽  
Vol 124 (3) ◽  
pp. 491-499 ◽  
Author(s):  
J. F. Roques ◽  
V. Dupont ◽  
J. R. Thome
Keyword(s):  
Heat Transfer ◽  
Low Flow ◽  
Film Condensation ◽  
Flow Mode ◽  
Water Mixture ◽  
Falling Film ◽  
Flow Rates ◽  
Enhanced Tubes ◽  
Plain Tube ◽  
Enhanced Boiling

In falling film heat transfer on horizontal tube bundles, liquid flow from tube to tube occurs as a falling jet that can take on different flow modes. At low flow rates, the liquid film falls as discrete droplets. At higher flow rates, these droplets form discretely spaced liquid columns. At still higher flow rates, the film falls as a continuous sheet of liquid. Predicting the flow transitions between these flow modes is an essential step in determining the heat transfer coefficient for the particular flow mode, whether for a single phase process or for falling film condensation or evaporation. Previous studies have centered mostly on falling films on plain tube arrays. The objective of the present study is to extend the investigation to tubes with enhanced surfaces: a low finned tube, an enhanced boiling tube and an enhanced condensation tube. The effect of tube spacing on flow transition has also been investigated. The test fluids were water, glycol and a glycol-water mixture. The adiabatic experimental results show that the flow mode transition thresholds for the enhanced boiling tube are very similar to those of the plain tube while the fin structure of the other two enhanced tubes can significantly shift their transition thresholds.

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