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Two Phase Flow Simulation Using Cellular Automata; Simulacion de Flujos de dos Fases con Automatas Celulares

Abstract

The classical mathematical treatment of two-phase flows is based on the average of the conservation equations for each phase.In this work, a complementary approach to the modeling of these systems based on statistical population balances of aut omata sets is presented.Automata are entities defined by mathematical states that change following iterative rules representing interactions with the neighborhood.A model of automata for two-phase flow simulation is presented.This model consists of fie lds of virtual spheres that change their volumes and move around a certain environment.The model is more general than the classical cellular automata in two respects: the grid of cellular automata is dismissed in favor of a trajectory generator, and the rules of interaction involve parameters representing the actual physical interactions between phases.Automata simulation was used to study unsolved two-phase flow problems involving high heat flux rates. One system described in this work consists of a vertical channel with saturated water at normal pressure heated from the lower surface.The heater causes water to boil and starts the bubble production.We used cellular automata to describe two-phase flows and the interaction with the heater.General rule s for such cellular automata representing bubbles moving in stagnant liquid were used, with special attention to  More>>
Authors:
Marcel, C P [1] 
  1. Instituto Balseiro, Universidad Nacional de Cuyo, Centro Atomico Bariloche (Argentina)
Publication Date:
Jul 01, 2002
Product Type:
Thesis/Dissertation
Report Number:
INIS-AR-V-073
Resource Relation:
Other Information: TH: Thesis (Ms.D); PBD: 2002
Subject:
42 ENGINEERING; BURNOUT; COMPUTERIZED SIMULATION; CRITICAL HEAT FLUX; HEAT TRANSFER; MASS TRANSFER; NUCLEATE BOILING; SIMULATION; TWO-PHASE FLOW; VOID FRACTION
OSTI ID:
20320713
Research Organizations:
Comision Nacional de Energia Atomica, San Carlos de Bariloche (Argentina). Dpto. de Ingenieria Nuclear e Investigacion Aplicada
Country of Origin:
Argentina
Language:
Spanish
Other Identifying Numbers:
TRN: AR03V0073010937
Availability:
Available from INIS in electronic form; Also available from marcelc@ib.cnea.gov.ar
Submitting Site:
INIS
Size:
100 pages
Announcement Date:
Feb 17, 2003

Citation Formats

Marcel, C P. Two Phase Flow Simulation Using Cellular Automata; Simulacion de Flujos de dos Fases con Automatas Celulares. Argentina: N. p., 2002. Web.
Marcel, C P. Two Phase Flow Simulation Using Cellular Automata; Simulacion de Flujos de dos Fases con Automatas Celulares. Argentina.
Marcel, C P. 2002. "Two Phase Flow Simulation Using Cellular Automata; Simulacion de Flujos de dos Fases con Automatas Celulares." Argentina.
@misc{etde_20320713,
title = {Two Phase Flow Simulation Using Cellular Automata; Simulacion de Flujos de dos Fases con Automatas Celulares}
author = {Marcel, C P}
abstractNote = {The classical mathematical treatment of two-phase flows is based on the average of the conservation equations for each phase.In this work, a complementary approach to the modeling of these systems based on statistical population balances of aut omata sets is presented.Automata are entities defined by mathematical states that change following iterative rules representing interactions with the neighborhood.A model of automata for two-phase flow simulation is presented.This model consists of fie lds of virtual spheres that change their volumes and move around a certain environment.The model is more general than the classical cellular automata in two respects: the grid of cellular automata is dismissed in favor of a trajectory generator, and the rules of interaction involve parameters representing the actual physical interactions between phases.Automata simulation was used to study unsolved two-phase flow problems involving high heat flux rates. One system described in this work consists of a vertical channel with saturated water at normal pressure heated from the lower surface.The heater causes water to boil and starts the bubble production.We used cellular automata to describe two-phase flows and the interaction with the heater.General rule s for such cellular automata representing bubbles moving in stagnant liquid were used, with special attention to correct modeling of different mechanisms of heat transfer.The results of the model were compared to previous experiments and correlations finding good agreement.One of the most important findings is the confirmation of Kutateladze's idea about a close relation between the start of critical heat flux and a change in the flow's topology.This was analyzed using a control volume located in the upper surface of the heater.A strong decrease in the interfacial surface just before the CHF start was encountered.The automata describe quite well some characteristic parameters such as the shape of the local void fraction in the channel. It was noticed that the CHF phenomena generally starts in cells located at the boundary.The fact that the phenomena can be well described by using simple rules shows that the related physics and even the physics with stochastic characteristics, has been captured with t his simple model. Some fractal properties of automata were also studied, arriving at the conclusion that the internal dynamics present fractal characteristics.Findings hint towards a new approach to solve open issues.Finally, a calculus related to the Australian reactor designed by INVAP was performed.The problem consists of a simulation of helium bubble production by the mechanism of mass diffusion in heavy water.It was verified that cellular automata systems are a powerful tool for describing problems with high complexity and short reach interactions between components.It was proved that two-phase flows could be described very well with this model.The approach is a powerful tool to describe non-equilibrium features, such as boiling flow development and interfacial topological transitions.A novel computer model of boiling crisis was encountered following this type of analysis.By means of this research, without invalidating the important advances obtained in other directions, a new tool is offered which can be useful regarding the modeling of boiling heat transfer systems.}
place = {Argentina}
year = {2002}
month = {Jul}
}