Assessment of an Interfacial Shear Term for Adiabatic Dispersed Air-Water Two-Phase Flow with the Two-Fluid Model

Abstract

In commercially available Computational Fluid Dynamics (CFD) codes such as ANSYS CFX and Fluent, the interfacial shear term is missing in the field momentum equations. The derivation of the two-fluid model (Ishii and Hibiki, 2011) indicates the presence of this term as a momentum source in the right hand side of the field momentum equation. The inclusion of this term is considered important for proper modeling of the interfacial momentum coupling between phases. For separated flows, such as annular flow, the importance of the shear term is understood in the one-dimensional (1-D) form as the major mechanism by which the wall shear is transferred to the gas phase (Mishima and Ishii, 1984). For dispersed two-phase flow CFD simulations it is important to assess the significance of this term in the prediction of phase distributions. In the first part of this work, the closure of this term in three- dimensional (3-D) form in a CFD code is investigated. For dispersed gas-liquid flow, such as bubbly or churn-turbulent flow, bubbles are dispersed in the shear layer of the continuous phase. The continuous phase shear stress is mainly due to the presence of the wall and the modeling of turbulence through the Boussinesq hypothesis. In a 3-D simulation, the continuous phase shear stress can be calculated from the continuous fluid velocity gradient, so that the interfacial shear term can be closed using the local values of the volume fraction and the total stress of liquid phase. This form also assures that the term acts as an action-reaction force for multiple phases. In the second part of this work, the effect of this term on the volume fraction distribution is investigated. For testing the model two-phase flow data measured at Purdue University is assessed. The interfacial shear term is assembled in ANSYS CFX. Simulation results are presented to assess the effect of the interfacial shear term on the phase distribution.

Meeting Name

International Topical Meeting on Nuclear Reactor Thermal Hydraulics 2015, NURETH-16 (2015, Aug. 30-Sep. 4, Chicago, IL)

Department(s)

Nuclear Engineering and Radiation Science

Keywords and Phrases

Air; Computational fluid dynamics; Fluids; Hydraulics; Liquids; Momentum; Nuclear reactors; One dimensional; Shear flow; Shear stress; Volume fraction; Air-water two phase flows; Computational Fluid Dynamics codes; Dispersed two-phase flows; Gas liquid flows; Interfacial shear; Threedimensional (3-d); Two fluid model; Volume fraction distribution; Two phase flow; CFD; Dispersed gas-liquid flow; Two-fluid model

International Standard Book Number (ISBN)

978-1-5108-1184-3

Document Type

Article - Conference proceedings

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2015 American Nuclear Society (ANS), All rights reserved.

Publication Date

01 Aug 2015

Link to Full Text

Share

 
COinS