Bulletin of the American Physical Society
75th Annual Meeting of the Division of Fluid Dynamics
Volume 67, Number 19
Sunday–Tuesday, November 20–22, 2022; Indiana Convention Center, Indianapolis, Indiana.
Session L20: Interface Modeling I |
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Chair: Fabien Evrard, Otto-von-Guericke-University; Marcus Herrmann, Arizona State University Room: 206 |
Monday, November 21, 2022 8:00AM - 8:13AM |
L20.00001: Geometric volume-of-fluid advection with parabolic interface reconstruction Fabien Evrard, Robert Chiodi, Berend van Wachem, Olivier Desjardins When simulating interfacial two-phase flows with the volume-of-fluid (VOF) method, the geometric advection of the volume fraction field requires the reconstruction of cellwise volume-preserving approximations of the interface. So far, the discretely conservative VOF advection schemes that have been proposed in the literature are limited to planar interface reconstructions, since these already present the challenge of intersecting non-trivial, non-convex polyhedra with a half-space. In this work, we present the first discretely conservative VOF advection scheme that uses parabolic interface reconstructions instead of planar ones. This is achieved by deriving the exact moments of the intersection between an arbitrary polyhedron and the space bounded by a paraboloid surface. In turn, this enables the solution of local constrained optimization problems for finding the optimal paraboloid surfaces matching the volume fractions around interfacial computational cells. We introduce and test several variants of this optimization problem. The resulting semi-Lagrangian advection scheme is validated with several classical three-dimensional test-cases, from which its order of accuracy and computational cost are assessed.
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Monday, November 21, 2022 8:13AM - 8:26AM |
L20.00002: A variational volume-of-fluid (VOF) approach to curvature-driven flows Ali Fakhreddine, Karim Alame, Krishnan Mahesh We introduce a variational volume-of-fluid methodology for evolving interfaces by curvature driven flow. The approach makes use of the traditional directionally split scheme to advect the fluid interface. Canonical two and three-dimensional geometries are tested with the formulation and the results are shown to match the physical behavior predicted by level-set methods with the additional advantage of interface sharpness and the lack of the need for interface “surgery”. The advecting velocities are also modified with a minimum curvature constraint for the same initial geometries and mass is shown to be conserved after minimum curvature is reached. |
Monday, November 21, 2022 8:26AM - 8:39AM |
L20.00003: A Dual Scale Approach to Predicting Sub-Filter Shear Driven Velocities on a Phase Interface with Vortex Sheet Method Austin C Goodrich, Marcus Herrmann A method to predict sub-filter velocities in the presence of shear on a liquid-gas phase interface for use in a dual scale LES-DNS model is presented. The method reconstructs the sub-filter velocity field on a Refined Local Surface Grid (RLSG) coaligned with the flow solver grid in a narrow band near the interface. A vortex sheet is employed at the interface location and evolves in time along with the interface by an unsplit geometric Volume-of-Fluid scheme using PLIC reconstruction and ELVIRA estimated normals. The shear-induced velocities due to the vortex sheet are evaluated in a vortex-in-cell type approach where a vorticity field is extrapolated to the underlying grid with a numerically smooth delta function. A stream function equation can then be constructed with the continuous vorticity distribution and solved to evaluate the self-induced vortex sheet velocities. The method is tested against results from prior literature and a comparison between the inviscid vortex sheet method and a viscous Navier-Stokes solution is presented. |
Monday, November 21, 2022 8:39AM - 8:52AM |
L20.00004: Modeling thin-film dynamics in multiscale volume-of-fluid simulations Austin Han, Olivier Desjardins In two-phase flow simulations utilizing the volume-of-fluid (VOF) method for interface capturing, the mesh size limits the characteristic length of the smallest resolvable features, which hinders the prediction of breakup. We present a computational framework to couple the VOF method to a thin-film model in underresolved fluid regions to accurately predict the thickness evolution of the film. A two-plane interface reconstruction in each cell and a connected-component labeling method for film identification facilitate a seamless transition between the VOF representation and the thin-film model. We demonstrate our method on a liquid sheet that thins down to subgrid scale due to flow kinematics and discuss implications for bag breakup modeling. |
Monday, November 21, 2022 8:52AM - 9:05AM |
L20.00005: A Dual Scale Approach to Large Eddy Simulations of Interfaces with Phase Change Marcus Herrmann, Austin C Goodrich, Dominic Kedelty A method to predict the sub-filter interfacial velocity of a liquid-gas phase interface with phase change for use in a dual scale Large Eddy Simulation (LES) model is presented. The method reconstructs the sub-filter velocity field on a Refined Local Surface Grid (RLSG) coaligned with the LES flow solver grid in a narrow band near the interface. Due to the mass transfer through the interface, the proposed model advects the phase interface normal to itself using the fully resolved interface normal vector available on the dual scale. The interface is transported with an unsplit geometric Volume-of-Fluid scheme using PLIC reconstruction and ELVIRA estimated normals to represent the interface. The dual scale method is tested and compared against DNS of a triply periodic box of decaying Homogeneous Isotropic Turbulence with an initially planar interface centered in the box. |
Monday, November 21, 2022 9:05AM - 9:18AM |
L20.00006: Implicit time schemes for simulating two-phase flows using diffuse interface methods on adaptive octree grids Makrand A Khanwale, Ali Mani The length scales needed to resolve for correct interfacial dynamics governed by diffuse interface methods and the associated velocity scales (governed by NS) are disparate. Specifically, for applications like contact line dynamics, where a small interface thickness parameter is needed, requiring fine mesh resolution to resolve the diffuse interface. We use fast octree-based adaptive meshes to resolve the diffuse interface to overcome this challenge. However, such a mesh adaption strategy leads to a prohibitively restrictive stability condition for explicit time schemes. Therefore, designing efficient and scalable implicit time schemes for diffuse interface methods becomes critical. Such implicit time schemes achieve stability for much larger time steps than explicit time schemes. This study assesses amenability and strategy constraints for designing implicit time schemes for second-order diffuse interface models compared to the fourth-order Cahn-Hilliard-based models. The time schemes are implemented with continuous Galerkin Finite Elements on adaptive octree meshes (AMR). The resulting framework with AMR and implicit time scheme is massively parallel and fast, potentially providing a leeway into simulating interface resolved two-phase flows. |
Monday, November 21, 2022 9:18AM - 9:31AM |
L20.00007: Iterative linear Solvers for High-Order Discretizations of Multiphase Flows Florian Kummer We are presenting multigrid-multilevel methods for a high-order multiphase flow solver, comparing different approaches for smothers. |
Monday, November 21, 2022 9:31AM - 9:44AM |
L20.00008: A Novel Boundary Layer Modeling Framework for Modeling Interfacial Mass Transport in Multiphase Flows Stephane L Zaleski, Jacob Maarek, Stéphane Popinet We present a new subgrid scale modeling framework for simulating interfacial mass transport in multi-phase flows. In the problem considered, the large Schmidt number leads to the formation of a thin concentration boundary layer at the interface potentially orders of magnitude smaller than the smallest hydrodynamic length scales. As such, fully resolving both hydrodynamic and mass transfer length scales results in prohibitive computational costs. Our framework developed in the Free Software library Basilisk performs a Direct Numerical Simulation of the flow field coupled with a subgrid model to simulate the transport of a concentration field. We use a concentration profile derived from the dominating terms in the transport equation to describe the distribution of mass in interfacial cells, consequently developing correction terms for advective and diffusive fluxes. The framework is profile-agnostic and can be used to model problems with a combination of dynamics present such as chemical reactions or phase change by applying an appropriate profile. Lastly we demonstrate how a shallow neural network can be used to approximate a boundary layer profile given by an equation or a dataset, simplifying the integration of new profiles in the framework. |
Monday, November 21, 2022 9:44AM - 9:57AM |
L20.00009: A contact line boundary condition for the second-order phase-field model Reed L Brown, Makrand A Khanwale, Shahab Mirjalili, Baskar Ganapathysubramanian, Ali Mani The diffuse interface method is a popular tool for simulating multiphase flows, and models that use the conservative 2nd-order phase field equation have many benefits over higher-order models, including bound preservation and faster computation. An ongoing challenge for such simulations is treatment of contact lines where the phase interface meets solid boundaries. A robust treatment requires attention to the details of coupling between the mass and momentum equations while honoring the added physics due to the diffuse nature of the interface. In this work, we present an asymptotically derived boundary treatment consistent with the diffuse nature of the interface and assess its performance over several canonical test cases. |
Monday, November 21, 2022 9:57AM - 10:10AM |
L20.00010: A second-order phase field model for simulation of N-phase flows Shahab Mirjalili, Ali Mani We present an N-phase extension to the second-order conservative phase field method. The proposed phase field model is in conservative form and is symmetric with respect to the phases while satisfying volume conservation. The model is reduction consistent, meaning that in the absence of M phases, the equations reduce to the equations for an N-M phase flow. Additionally, the boundedness properties of the two-phase model are inherited by the N-phase model. We show that this phase field model allows for variable interface thicknesses between different phases. For coupling to momentum transport, we extend the two-phase mass-momentum consistent model to N-phase flows. Using second-order central spatial schemes, the resulting N-phase flow solver is not only mass-momentum consistent, but also inherits the conservation properties of its two-phase version, resulting in the first N-phase flow method that analytically and discretely conserves mass, momentum and kinetic energy (in the absence of capillary and viscous effects). A novel surface tension model is proposed for surface tension forces. Using multiple numerical tests, we show that our fully coupled N-phase flow solver boasts high accuracy in simulating N-phase flows. |
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