Large Interface Simulation in Multiphase Flow Phenomena

2006 ◽  
Author(s):  
Aparicio Henriques ◽  
Pierre Coste ◽  
Sylvain Pigny ◽  
Jacques Magnaudet
Keyword(s):  
Free Surface ◽  
Large Scale ◽  
Fluid Model ◽  
Surface Tension Force ◽  
Recognition Algorithm ◽  
Small Scale ◽  
Rising Bubble ◽  
Flow Phenomena ◽  
Two Fluid Model ◽  
Two Fluid

An attempt to represent multiphase multiscale flow, filling the gap between Direct Numerical Simulation (DNS) and averaged approaches, is the purpose of this paper. We present a kind of Large Interface (LI) simulation formalism obtained after a filtering process on local instantaneous conservation equations of the two-fluid model which distinguishes between small scales and large scales contributions. LI surface tension force is also taken into account. Small scale dynamics call for modelisation and large scale for simulation. Joined to this formalism, a criterion to recognize LI’s is developped. It is used in an interface recognition algorithm which is qualified on a sloshing case and a bubble oscillation under zero-gravity. This method is applied to a rising bubble in a pool that collapses at a free surface and to a square-base basin experiment where splashing and sloshing at the free surface are the main break-up phenomena.

scholarly journals Simulation of Free Surface Compressible Flows via a Two Fluid Model

2008 ◽  
Author(s):  
Fre´de´ric Dias ◽  
Denys Dutykh ◽  
Jean-Michel Ghidaglia
Keyword(s):  
Free Surface ◽  
Wave Breaking ◽  
Compressible Flows ◽  
Fluid Model ◽  
Three Dimensional ◽  
Two Fluids ◽  
Equation Of States ◽  
Two Fluid Model ◽  
Velocity Pressure ◽  
Two Fluid

The purpose of this communication is to discuss the simulation of a free surface compressible flow between two fluids, typically air and water. We use a two fluid model with the same velocity, pressure and temperature for both phases. In such a numerical model, the free surface becomes a thin three dimensional zone. The present method has at least three advantages: (i) the free-surface treatment is completely implicit; (ii) it can naturally handle wave breaking and other topological changes in the flow; (iii) one can easily vary the Equation of States (EOS) of each fluid (in principle, one can even consider tabulated EOS). Moreover, our model is unconditionally hyperbolic for reasonable EOS.

Numerical Simulation of Rayleigh-Taylor Instability With Two-Fluid Model and Interface Sharpening

2008 ◽  
Author(s):  
Luka Sˇtrubelj ◽  
Iztok Tiselj
Keyword(s):  
Free Surface ◽  
Level Set ◽  
Fluid Model ◽  
Free Surface Flows ◽  
Taylor Instability ◽  
Surface Flows ◽  
Interface Diffusion ◽  
Rayleigh Taylor Instability ◽  
Two Fluid Model ◽  
Two Fluid

The free surface flows are successfully modeled with one of the existing free surface models, such as: level set method, volume of fluid method, front tracking method, two-fluid model (two momentum equations) with modified interphase force and some others. The main disadvantage of the two-fluid model used for simulations of free surface flows is numerical diffusion of the interface, which can be significantly reduced as presented in this paper. The interface is sharpened with the conservative level set method, where after the advection step of volume fraction the numerical diffusion of the interface is reduced in such a way that the thickness of the interface is kept constant during the simulation. The reduction of the interface diffusion can also be called interface sharpening. In the present paper the two-fluid model with interface sharpening is validated with Rayleigh-Taylor instability. Under assumptions of isothermal and incompressible flow of two immiscible fluids, we simulated a system with the fluid of higher density located above the fluid of smaller density in two dimensions. Due to the gravity in the system, the fluid with a higher density moves below the fluid with a smaller density. The initial condition is not a flat interface between the fluids, but a cosine wave with small amplitude, which develops into a mushroom-like structure. Mushroom-like structure in simulation of Rayleigh-Taylor instability later develops into small droplets as result of numerical dispersion of interface (interface sharpening) or to narrow trails with interface diffusion (no interface sharpening). The results of the two-fluid model with interface sharpening are compared to two-fluid model without interface sharpening and single-fluid-model with/without interface sharpening. The analytic solution of amplitude growth can be found for small amplitudes and was also compared to simulation.

ELECTRON PARALLEL COMPRESSIBILITY IN THE NONLINEAR DEVELOPMENT OF TWO-DIMENSIONAL COLLISIONLESS MAGNETOHYDRODYNAMIC RECONNECTION

2006 ◽  
Vol 20 (16) ◽  
pp. 931-961 ◽  
Author(s):  
DANIELE DEL SARTO ◽  
F. CALIFANO ◽  
F. PEGORARO
Keyword(s):  
Magnetic Reconnection ◽  
Fluid Model ◽  
Density Fluctuations ◽  
Larmor Radius ◽  
Small Scale ◽  
Two Dimensional ◽  
Guide Field ◽  
Fluid Instabilities ◽  
Two Fluid Model ◽  
Two Fluid

Some topological aspects of the magnetic reconnection phenomenon are summarized and recent numerical results, derived within a two-fluid model, of two-dimensional collisionless magnetic reconnection in presence of a strong guide field are reported. Both the Alfvèn and the whistler frequency range are investigated by including electron parallel compressibility effects that are related respectively to thermal effects and to density fluctuations. The Hamiltonian character of the system is emphasized as it drives the small scale dynamics through the presence of topological invariants. These determine the formation and the shape of small scale current and vorticity layers inside the magnetic island. Secondary fluid instabilities, mainly of the Kelvin–Helmholtz type, can destabilize these layers when a hydrodynamic type regime is achieved. The inclusion of parallel electron compressibility has stabilizing effects. In view of the limitations of the two-fluid modelling, possible developments are briefly discussed such as the inclusion of Larmor-radius corrections, in lieu of a fully kinetic approach.

A two-fluid model with a tensor closure model approach for free surface flow simulations

2015 ◽  
Vol 122 ◽  
pp. 596-613 ◽  
Author(s):  
Ricardo V.P. Rezende ◽  
Regiani A. Almeida ◽  
Antônio A. Ulson de Souza ◽  
Selene M.A. Guelli U. Souza
Keyword(s):  
Free Surface ◽  
Fluid Model ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Closure Model ◽  
Flow Simulations ◽  
Two Fluid Model ◽  
Two Fluid ◽  
Model Approach

scholarly journals Two-Fluid Model Approach for Transient Analysis of Free-Surface-Pressurized Flows.

2001 ◽  
Vol 67 (659) ◽  
pp. 1742-1748
Author(s):  
Kazutoshi ARAI ◽  
Youhei HASEGAWA ◽  
Katsuhiro YAMAMOTO ◽  
Shunsuke SHIMIZU
Keyword(s):  
Free Surface ◽  
Transient Analysis ◽  
Fluid Model ◽  
Pressurized Flows ◽  
Two Fluid Model ◽  
Two Fluid ◽  
Model Approach

A spatially-averaged two-fluid model for dense large-scale gas-solid flows

AIChE Journal ◽  
2017 ◽  
Vol 63 (8) ◽  
pp. 3544-3562 ◽  
Author(s):  
Simon Schneiderbauer
Keyword(s):  
Large Scale ◽  
Fluid Model ◽  
Two Fluid Model ◽  
Two Fluid

Scaling Methodology for the Direct ECC Bypass During LBLOCA Reflood Phase With Direct Vessel Injection System: Its Development and Validation

2002 ◽  
Author(s):  
H. K. Cho ◽  
B. J. Yun ◽  
T. S. Kwon ◽  
C.-H. Song ◽  
G. C. Park
Keyword(s):  
Fluid Model ◽  
Scaling Law ◽  
Injection System ◽  
Linear Scaling ◽  
Experimental Facility ◽  
Flow Phenomena ◽  
Two Fluid Model ◽  
Development And Validation ◽  
Two Fluid ◽  
Type Parameter

From the two dimensional two-fluid model a new scaling methodology, named the “modified linear scaling”, is suggested for the scientific design of a scaled-down experimental facility and data analysis of the direct ECC bypass under LBLOCA reflood phase. The characteristics of the scaling law are its velocity is scaled by a Wallis-type parameter and the aspect ratio of experimental facility is preserved with that of prototype. For the experimental validation of the proposed scaling law, the air-water tests for direct ECC bypass were performed in the 1/4.0 and 1/7.3 scaled UPTF downcomer test section. The obtained data are compared with those of UPTF Test21-D. It is found that the modified linear scaling methodology is appropriate for the preservation of multi-dimensional flow phenomena in downcomer annulus, such as direct ECC bypass.

Two-Fluid Model Approach for Transient Analysis of Mixed Free-Surface Pressure Flow

2000 ◽  
Vol 2000 (0) ◽  
pp. 136
Author(s):  
Kazutoshi ARAI ◽  
Youhei HASEGAWA ◽  
Shinya MORI ◽  
Shunsuke SHIMIZU ◽  
Katsuhiro YAMAMOTO
Keyword(s):  
Free Surface ◽  
Surface Pressure ◽  
Transient Analysis ◽  
Fluid Model ◽  
Pressure Flow ◽  
Two Fluid Model ◽  
Two Fluid ◽  
Model Approach
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