Spurious velocity from the cutoff and magnification equation in free energy-based LBM for two-phase flow with a large density ratio

2019 ◽  
Vol 78 (4) ◽  
pp. 1166-1181 ◽  
Author(s):  
Jiaming Gong ◽  
Nobuyuki Oshima ◽  
Yutaka Tabe
Keyword(s):  
Free Energy ◽  
Two Phase Flow ◽  
Density Ratio ◽  
Phase Flow ◽  
Two Phase ◽  
Large Density ◽  
Large Density Ratio

A Validated Two-Phase Flow Large Eddy Simulation Methodology

2013 ◽  
Author(s):  
Feng Xiao ◽  
Mehriar Dianat ◽  
James J. McGuirk
Keyword(s):  
Boundary Conditions ◽  
Level Set ◽  
Two Phase Flow ◽  
Local Level ◽  
Density Ratio ◽  
Cross Flow ◽  
Liquid Jet ◽  
Phase Flow ◽  
Two Phase ◽  
Primary Breakup

A robust two-phase flow LES methodology is described, validated and applied to simulate primary breakup of a liquid jet injected into an airstream in either co-flow or cross-flow configuration. A Coupled Level Set and Volume of Fluid method is implemented for accurate capture of interface dynamics. Based on the local Level Set value, fluid density and viscosity fields are treated discontinuously across the interface. In order to cope with high density ratio, an extrapolated liquid velocity field is created and used for discretisation in the vicinity of the interface. Simulations of liquid jets discharged into higher speed airstreams with non-turbulent boundary conditions reveals the presence of regular surface waves. In practical configurations, both air and liquid flows are, however, likely to be turbulent. To account for inflowing turbulent eddies on the liquid jet interface primary breakup requires a methodology for creating physically correlated unsteady LES boundary conditions, which match experimental data as far as possible. The Rescaling/Recycling Method is implemented here to generate realistic turbulent inflows. It is found that liquid rather than gaseous eddies determine the initial interface shape, and the downstream turbulent liquid jet disintegrates much more chaotically than the non-turbulent one. When appropriate turbulent inflows are specified, the liquid jet behaviour in both co-flow and cross-flow configurations is correctly predicted by the current LES methodology, demonstrating its robustness and accuracy in dealing with high liquid/gas density ratio two-phase systems.

A Preconditioned Implicit Free-Surface Capture Scheme for Large Density Ratio on Tetrahedral Grids

2012 ◽  
Vol 11 (1) ◽  
pp. 215-248 ◽  
Author(s):  
Xin Lv ◽  
Qingping Zou ◽  
D.E. Reeve ◽  
Yong Zhao
Keyword(s):  
Free Surface ◽  
Density Ratio ◽  
Three Dimensional ◽  
Integration Scheme ◽  
Two Phase ◽  
Fully Implicit ◽  
Large Density ◽  
Multi Stage ◽  
Tetrahedral Grids ◽  
Large Density Ratio

AbstractWe present a three dimensional preconditioned implicit free-surface capture scheme on tetrahedral grids. The current scheme improves our recently reported method [10] in several aspects. Specifically, we modified the original eigensystem by applying a preconditioning matrix so that the new eigensystem is virtually independent of density ratio, which is typically large for practical two-phase problems. Further, we replaced the explicit multi-stage Runge-Kutta method by a fully implicit Euler integration scheme for the Navier-Stokes (NS) solver and the Volume of Fluids (VOF) equation is now solved with a second order Crank-Nicolson implicit scheme to reduce the numerical diffusion effect. The preconditioned restarted Generalized Minimal RESidual method (GMRES) is then employed to solve the resulting linear system. The validation studies show that with these modifications, the method has improved stability and accuracy when dealing with large density ratio two-phase problems.

Vibration of a Tube Bundle in Two-Phase Freon Cross-Flow

1995 ◽  
Vol 117 (4) ◽  
pp. 321-329 ◽  
Author(s):  
M. J. Pettigrew ◽  
C. E. Taylor ◽  
J. H. Jong ◽  
I. G. Currie
Keyword(s):  
Two Phase Flow ◽  
Tube Bundle ◽  
Density Ratio ◽  
Cross Flow ◽  
Flow Regimes ◽  
Phase Flow ◽  
Two Phase ◽  
Void Fractions ◽  
Fluidelastic Instability ◽  
First Results

Two-phase cross-flow exists in many shell-and-tube heat exchangers. The U-bend region of nuclear steam generators is a prime example. Testing in two-phase flow simulated by air-water provides useful results inexpensively. However, two-phase flow parameters, in particular surface tension and density ratio, are considerably different in air-water than in steam-water. A reasonable compromise is testing in liquid-vapor Freon, which is much closer to steam-water while much simpler experimentally. This paper presents the first results of a series of tests on the vibration behavior of tube bundles subjected to two-phase Freon cross-flow. A rotated triangular tube bundle of tube-to-diameter ratio of 1.5 was tested over a broad range of void fractions and mass fluxes. Fluidelastic instability, random turbulence excitation, and damping were investigated. Well-defined fluidelastic instabilities were observed in continuous two-phase flow regimes. However, intermittent two-phase flow regimes had a dramatic effect on fluidelastic instability. Generally, random turbulence excitation forces are much lower in Freon than in air-water. Damping is very dependent on void fraction, as expected.

LBM Application in Two-Phase Fluid Flow with Large Density Ratio

2012 ◽  
Vol 476-478 ◽  
pp. 871-875
Author(s):  
Qing Ming Chang ◽  
Yin Kai Yang ◽  
Jing Yuan ◽  
Xia Chen ◽  
Min Zhang
Keyword(s):  
Gravity Wave ◽  
Numerical Solutions ◽  
Density Ratio ◽  
Surface Tension Force ◽  
Analytic Solutions ◽  
Lattice Boltzmann Model ◽  
Two Phase ◽  
Large Density ◽  
Large Density Ratio ◽  
Parasitic Currents

In this paper, a stable lattice Boltzmann model (LBM) based on non-ideal gases is presented for simulation of incompressible two-phase flows with large density ratio. To reduce the parasitic currents across the interface and correspondingly increase the numerical stability, the stress and potential forms of the surface tension force is employed. The applications to a stationary bubble and capillary-gravity wave with density ratio 1000 are given to verify this model. The numerical solutions is agree well with analytic solutions of the Laplace's law and capillary-gravity wave.

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