Abstract
Commercial code CFX was used to examine the performance of a two-fluid model to predict the details of upward isothermal bubbly flow of air and water in a vertical pipe. The model equations are volume-averaged Navier-Stokes equations that require closure models for interfacial forces and bubble-induced turbulence effects. Two-equation SST and k-epsilon RANS turbulence models were also used. A parametric study of closure models included both standard options in CFX and previously published novel closure models that were implemented with user-defined functions. The CFD simulations were compared with two cases from the MTLoop experiments by Lucas et al. at the Helmholtz-Zentrum Dresden Rossendorf: one with wall-peak void fraction profile (MT039), and another with a core-peak void fraction profile (MT118). The effect of changing the drag force closures was not significant for the set examined. Poor predictions were found when the lift force and wall lubrication models were incompatible in magnitude. There was no significant effect of changing the liquid phase turbulence model. Changing the bubble-induced turbulence models, however, had a significant impact on the radial void fraction profile. The novel wall force from Lubchenko et al. at the Massachusetts Institute of Technology significantly improved the prediction of the near wall void fraction in the wall peak profile.
Highlights
Two-phase gas-liquid flows occur in many important industrial processes
The lateral lift and wall lubrication models can be varied independently, it is difficult to isolate the physical accuracy of either closure model. Because both lateral lift and wall lubrication force act normal to the wall and their effective regions overlap, the net effect of the two is what influences the prediction of the radial void profile
Vertical bubbly flow in a vertical pipe was modelled using commercial computational fluid dynamics (CFD) code ANSYS CFX
Summary
Two-phase gas-liquid flows occur in many important industrial processes. It is challenging to gain a strong understanding of such flows because of the complex physical interactions between the phases that often occur. J. Ormiston plex flow structures can be found, depending on the flow geometry, orientation, fluid properties, and the mass flow rates of gas and liquid. The capability to predict the two-phase flow behaviour would be a valuable tool in the design of important industrial equipment, so the development of suitable computational fluid dynamics (CFD) models is an active area of ongoing research
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
