Abstract
This paper presents an enstrophy-resolved simulation of the phase inversion problem using the volume of fluid (VOF) method. This well-known benchmark for modeling multiphase flows features a buoyancy-driven unsteady motion of a light fluid into a heavy one followed by several large- and small-scale interfacial processes such as deformation, ligament formation, interface breakup, and coalescence. A fully resolved description of such flow is advantageous for a priori and a posteriori evaluations when developing new subgrid-scale closure models for large eddy simulation of two-phase flows. However, most of the previous attempts in performing the direct numerical simulation of this problem have been unsuccessful to reach grid-independent high-order flow statistics such as enstrophy. The key contribution of this paper lies in proposing a new converging configuration for this problem by reducing the Reynolds and Weber numbers. The new setup reaches grid convergence for all the flow characteristics on a 512^3 grid. Particularly, the enstrophy which has always revealed a grid-dependent behavior in all the previous studies converges for the proposed setup. Also, we analyze the temporal evolution of interfacial structures including the statistics of the total interfacial area during the process on different grid resolutions. First, no convergence on the interfacial area is observed and the possible reasons for lack of convergence are discussed. The potential remedies are investigated through a comprehensive parameter study. The findings highlight that (i) the enstrophy always converges for these moderate Re and We numbers, and (ii) the convergence of the total interfacial area is sensitive to the choice of initial and wall boundary conditions. Then, a new setup based on this sensitivity analysis is proposed that succeeded in full convergence for enstrophy and a partial convergence for the total interfacial area. The numerical simulations were carried out using the VOF solvers of OpenFOAM with a comparison between the algebraic and geometric schemes. Besides, the convergence of size distribution of dispersed structures is investigated. The present study provides insight into the possible directions toward a DNS of phase inversion problem with all the flow and interfacial structures resolved, which is essential for the future development of multiphase flow models.
Highlights
Modeling and simulation of multiscale two-phase flows in the presence of interfaces has been a prominent research topic in fluid mechanics and heat transfer
The continuous growth of computational capacities brought by massively parallel clusters has nowadays allowed to significantly improve the understanding of highly unsteady and turbulent multiphase flows by performing direct numerical simulation (DNS)
The volume of fluid (VOF) simulation of the phase inversion problem is presented for a configuration that provides the grid convergence in different first- and second-order statistics of the flow
Summary
Modeling and simulation of multiscale two-phase flows in the presence of interfaces has been a prominent research topic in fluid mechanics and heat transfer. A wide spectrum of real-life applications from controlling the fuel injection, engine pollution, and light material design in the aeronautical industry to various engineering processes such as oil transport, steel manufacturing, and nuclear safety benefit from model development for twophase interfacial flows, in particular when the turbulence is involved In all these applications, the physical core phenomenon consists of multiphase flow with interfaces between immiscible fluids which in turn are subject to unsteady or turbulent interactions and impart a wide range of spatial and temporal scales from micron to meter and micro-second to minute. Such reference solutions have to be defined with simple initial and forcing conditions in a way that a DNS becomes practical on a reasonable grid resolution (less than 109 grid points) They have to exhibit unsteady (or turbulent) behavior for both flow and two-phase characteristics, including deformation, rupture, and coalescence of interfacial structures and represent the interactions between flow turbulence and multiphase physics. It does not lie within the scope of the present study
Sign-in/Register to view highlights & summary 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 callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
