An Evaluation of a Two-Fluid Eulerian-Liquid Eulerian-Gas Model for Diesel Sprays

2003 ◽  
Vol 125 (4) ◽  
pp. 660-669 ◽  
Author(s):  
Venkatraman Iyer ◽  
John Abraham
Keyword(s):  
Fluid Model ◽  
Near Field ◽  
Far Field ◽  
Diesel Sprays ◽  
Jet Breakup ◽  
Wide Range ◽  
Numerical Grid ◽  
Two Fluid Model ◽  
Grid Independence ◽  
Two Fluid

A two fluid Eulerian-liquid Eulerian-gas (ELEG) model for diesel sprays is developed. It is employed to carry out computations for diesel sprays under a wide range of ambient and injection conditions. Computed and measured results are compared to assess the accuracy of the model in the far field, i.e., at axial distances greater than 300 orifice diameters, and in the near field, i.e., at axial distances less than 100 orifice diameters. In the far field, the comparisons are of drop mean velocities and drop fluctuation velocities and in the near field they are of entrainment velocities and entrainment constants. Adequate agreement is obtained quantitatively, within 30 percent, and qualitatively as parameters are changed. Unlike in traditional Lagrangian-drop Eulerian-fluid (LDEF) approaches that are employed for diesel spray computations, adequate resolution can be employed in the near field to achieve numerical grid independence when the two-fluid model is employed. A major source of uncertainty in the near field is in the modeling of liquid jet breakup and atomization.

Study on Drag Coefficients for Two Groups of Bubbles

2004 ◽  
Author(s):  
Xiaodong Sun ◽  
Yang Liu ◽  
Basar Ozar ◽  
Mamoru Ishii ◽  
Joseph M. Kelly
Keyword(s):  
Gas Phase ◽  
Fluid Model ◽  
Interfacial Area ◽  
Current Approach ◽  
Two Phase ◽  
Drag Coefficients ◽  
Interfacial Area Transport ◽  
Wide Range ◽  
Two Fluid Model ◽  
Two Fluid

To apply the two-fluid model to a wide range of flow regimes in gas-liquid two-phase flows, the gas phase is categorized into two groups: small spherical/distorted bubbles as Group 1 and large cap/slug/churn-turbulent bubbles as Group 2 in the modeling of interfacial area transport. The interfacial transfer terms of momentum and energy for the gas phase are then divided into two groups accordingly in the implementation of the two-group interfacial area transport equation to the two-fluid model. Thus, the drag coefficients and the interfacial heat transfer for each group bubbles need to be developed. An approach has been sought for evaluating the drag coefficients of each bubble group based on a comprehensive experimental data base obtained in air-water upward flows in various size round pipes. Comparisons have been made with the theory of the drag coefficients and it was found that the agreement is not very satisfactory although the general trends can be predicted by the current approach.

Assessment of Components of the Subcooled Boiling Model for CFD Simulations

2010 ◽  
Author(s):  
Deoras Prabhudharwadkar ◽  
Martin A. Lopez de Bertodano ◽  
John Buchanan ◽  
Avinash Vaidheeswaran
Keyword(s):  
Fluid Model ◽  
Constitutive Relations ◽  
Bubble Diameter ◽  
Density Ratio ◽  
Data Sets ◽  
Vapor Generation ◽  
Wide Range ◽  
Two Fluid Model ◽  
Bubble Sizes ◽  
Two Fluid

This paper describes the details of validation of heat and mass transfer models used for subcooled boiling simulation with a CFD two-fluid model. This research was focused on assessment of the wall heat flux partitioning model using the state-of-the-art multidimensional experimental data available in the literature. Various constitutive relations used to close the vapor generation rate at the heated wall were studied and the best suited combination of these was obtained. The current study was restricted to vertical flows through pipe and annulus geometries. Three data sets from the literature were considered: first with R12 at about 26 bar pressure, second with water at atmospheric pressure and third with R113 at 2.69 bar pressure. In these data sets, the bubble diameter distribution across the ducts was measured. Bubble diameter estimation brings in the largest uncertainty in the two-fluid model predictions and hence using the data with known bubble sizes allowed to focus on assessment of other parameters which use constitutive relations to model vapor generation rate, e.g. bubble nucleation site density and bubble departure frequency at the wall. The simulations were carried out using the CFD code CFX-12. The R12 data used here corresponds to fluid-vapor density ratio which is equivalent to that of water-steam at 150 bar. Therefore the density ratio varies over two orders of magnitude. The surface tension also varies over a wide range from 0.0017 to 0.057 N/m. The ratio of the flow channel hydraulic diameter to the bubble diameter in these simulations varied between 4 and 40. The two-fluid model was modified, for cases involving bubble sizes too large to be represented using the continuum assumption, in order to obtain satisfactory results. Hence, the model that has been developed for this study is applicable for a wide range of physical conditions and bubble sizes.

scholarly journals Sub-grid Scale Modelling and a-Posteriori Tests with a Morphology Adaptive Multifield Two-Fluid Model Considering Rising Gas Bubbles

2021 ◽  
Author(s):  
R. Meller ◽  
F. Schlegel ◽  
M. Klein
Keyword(s):  
Hybrid Model ◽  
Fluid Model ◽  
Three Dimensional ◽  
Gas Bubbles ◽  
A Posteriori ◽  
Interfacial Structures ◽  
Numerical Grid ◽  
Two Fluid Model ◽  
Liquid Flows ◽  
Two Fluid

AbstractThe predictive simulation of gas–liquid multiphase flows at industrial scales reveals the challenging task to consider turbulence and interfacial structures, which span a large range of length scales. For simulation of relevant applications, a hybrid model can be utilised, which combines the Euler–Euler model for the description of small interfacial structures with a volume-of-fluid model as a scale-resolving multiphase approach. Such a hybrid model needs to be able to simulate interfaces, which are hardly resolved on a coarse numerical grid. The goal of this work is to improve the prediction of interfacial gas–liquid flows on a numerical grid with comparably large grid spacing. From the low-pass filtering of the two-fluid model five unclosed sub-grid scale terms arise. The convective and the surface tension part of the aforementioned contributions are individually modelled with multiple closure formulations. Those models are a-posteriori assessed in cases of two- and three-dimensional gas bubbles rising in stagnant liquid. It is shown, that the chosen closure modelling approach is suitable to improve the predictive power of the numerical model utilised in this work. Hence, simulation results on comparably coarse grids are changed towards results obtained with higher spatial resolution.

scholarly journals Natural modes of the two-fluid model of two-phase flow

2021 ◽  
Vol 33 (3) ◽  
pp. 033324
Author(s):  
Alejandro Clausse ◽  
Martín López de Bertodano
Keyword(s):  
Two Phase Flow ◽  
Fluid Model ◽  
Phase Flow ◽  
Two Phase ◽  
Natural Modes ◽  
Two Fluid Model ◽  
Two Fluid

Self-consistent hydrodynamic two-fluid model of vortex plasma

2021 ◽  
Vol 33 (3) ◽  
pp. 037116
Author(s):  
Victor L. Mironov
Keyword(s):  
Fluid Model ◽  
Self Consistent ◽  
Two Fluid Model ◽  
Two Fluid
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