Group Title: 7th International Conference on Multiphase Flow - ICMF 2010 Proceedings
Title: P2.34 - DNS up-scaling applied to two-phase momentum balance and volumetric interfacial area transport equation for a vertical bubbly flow
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Permanent Link: http://ufdc.ufl.edu/UF00102023/00488
 Material Information
Title: P2.34 - DNS up-scaling applied to two-phase momentum balance and volumetric interfacial area transport equation for a vertical bubbly flow Bubbly Flows
Series Title: 7th International Conference on Multiphase Flow - ICMF 2010 Proceedings
Physical Description: Conference Papers
Creator: Magdeleine, S.
Mathieu, B.
Lebaigue, O.
Toutant, A.
Morel, C.
Publisher: International Conference on Multiphase Flow (ICMF)
Publication Date: June 4, 2010
 Subjects
Subject: two-phase flow
DNS
ISS
LES
scale similarity
pseudo-turbulence
a priori test
bubble swarm
drag coefficient
 Notes
Abstract: In the quest for a better description of the thermal-hydraulics of a PWR sub-channel by using DNS results to upscale valuable information towards higher scale industrial models, two main tasks have been identified and tackled separately. The first one is dedicated to the simulation of adiabatic turbulent two-phase flows in a sub-channel. The second one is dedicated to phase change aspects (see, e.g., Bois et al. (2010), same Conference) and to wall nucleate boiling (see, e.g., Mathieu (2004)). The present contribution is related to the first task, namely focusing on an adiabatic bubble swarm in an upwards vertical flow. The flow situation considered in the present paper corresponds to a situation with a large number of bubbles: the domain can be crossed simultaneously by more than 5,000 deformable bubbles. To progress from simpler monodisperse bubbly flow, a bidisperse bubbly flow is used to gain more elaborate information. Of course, neither the number of bubbles nor the bidisperse features are enough to cover the variety of existing industrial bubble swarms; nevertheless, this case is the basis on which a new methodology is developed: ISS is developed and validated as a DNS-like tool to perform an accurate description of the bubbly flow. ISS has been proposed (Toutant et al. (2007)) as a two-phase equivalent to single-phase LES; ISS takes care of the subgrid part of the transfer across the interface, especially the momentum transfer that occurs at the smallest scales. Sub-grid models are mostly analogous to Bardina’s scale similarity ones and include effects of the interface micro-scales and of the fluid eddies close to these interfaces. A large computation is performed and its results are space- and time-averaged to extract relevant statistics needed to up-scale the physics to averaged models. The void fraction is still moderate (up to 4%) but it provides information on the effects of the collective motion of the bubble swarm. Space- and time-averaged quantities computed from the DNS (e.g., drag coefficient and forces applied by one phase on the other) are compared with standard correlations and classical models. The proposed LES-like model opens new perspectives towards complex simulations of bubble swarms with explicit interface tracking at reasonable computational cost. The effects of bi- and poly-disperse distribution can be studied in detail by such an approach. The analyses of the results confirm that the interfacial area Ai transport velocity differs from gas velocity in bidisperse flow; moreover, it confirms that classical two-fluid models are relevant for monodisperse flows whereas an improved model is needed for uncorrelated Ai fluxes that occurs in bidisperse flow. Additional results concern the drag coefficient, the phase pressures and the forces exerted by one phase on the other. For all these quantities, classical models build with a monodisperse flavour have poor prediction capabilities!
General Note: The International Conference on Multiphase Flow (ICMF) first was held in Tsukuba, Japan in 1991 and the second ICMF took place in Kyoto, Japan in 1995. During this conference, it was decided to establish an International Governing Board which oversees the major aspects of the conference and makes decisions about future conference locations. Due to the great importance of the field, it was furthermore decided to hold the conference every three years successively in Asia including Australia, Europe including Africa, Russia and the Near East and America. Hence, ICMF 1998 was held in Lyon, France, ICMF 2001 in New Orleans, USA, ICMF 2004 in Yokohama, Japan, and ICMF 2007 in Leipzig, Germany. ICMF-2010 is devoted to all aspects of Multiphase Flow. Researchers from all over the world gathered in order to introduce their recent advances in the field and thereby promote the exchange of new ideas, results and techniques. The conference is a key event in Multiphase Flow and supports the advancement of science in this very important field. The major research topics relevant for the conference are as follows: Bio-Fluid Dynamics; Boiling; Bubbly Flows; Cavitation; Colloidal and Suspension Dynamics; Collision, Agglomeration and Breakup; Computational Techniques for Multiphase Flows; Droplet Flows; Environmental and Geophysical Flows; Experimental Methods for Multiphase Flows; Fluidized and Circulating Fluidized Beds; Fluid Structure Interactions; Granular Media; Industrial Applications; Instabilities; Interfacial Flows; Micro and Nano-Scale Multiphase Flows; Microgravity in Two-Phase Flow; Multiphase Flows with Heat and Mass Transfer; Non-Newtonian Multiphase Flows; Particle-Laden Flows; Particle, Bubble and Drop Dynamics; Reactive Multiphase Flows
 Record Information
Bibliographic ID: UF00102023
Volume ID: VID00488
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: P234-Magdeleine-ICMF2010.pdf

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