Bulletin of the American Physical Society
69th Annual Meeting of the APS Division of Fluid Dynamics
Volume 61, Number 20
Sunday–Tuesday, November 20–22, 2016; Portland, Oregon
Session A12: Multiphase Flows: Recent Advances in Numerical Methods |
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Chair: Brian Turnquist, Montana State University Room: C123 |
Sunday, November 20, 2016 8:00AM - 8:13AM |
A12.00001: Intrusive Method for Uncertainty Quantification in a Multiphase Flow Solver Brian Turnquist, Mark Owkes Uncertainty quantification (UQ) is a necessary, interesting, and often neglected aspect of fluid flow simulations. To determine the significance of uncertain initial and boundary conditions, a multiphase flow solver is being created which extends a single phase, intrusive, polynomial chaos scheme into multiphase flows. Reliably estimating the impact of input uncertainty on design criteria can help identify and minimize unwanted variability in critical areas, and has the potential to help advance knowledge in atomizing jets, jet engines, pharmaceuticals, and food processing. Use of an intrusive polynomial chaos method has been shown to significantly reduce computational cost over non-intrusive collocation methods such as Monte-Carlo. This method requires transforming the model equations into a weak form through substitution of stochastic (random) variables. Ultimately, the model deploys a stochastic Navier Stokes equation, a stochastic conservative level set approach including reinitialization, as well as stochastic normals and curvature. By implementing these approaches together in one framework, basic problems may be investigated which shed light on model expansion, uncertainty theory, and fluid flow in general. [Preview Abstract] |
Sunday, November 20, 2016 8:13AM - 8:26AM |
A12.00002: Marker Re-Distancing and Sharp Reconstruction for High-Order Multi-Material Interface Evolution Robert Nourgaliev, Patrick Greene, Sam Schofield A new method for high-order front evolution on arbitrary meshes is introduced. The method is a hybrid of a Lagrangian marker tracking with a Discontinuous Galerkin projection based level set re-distancing. This Marker-Re-Distancing (MRD) method is designed to work accurately and robustly on unstructured, generally highly distorted meshes, necessitated by applications within ALE-based hydro-codes. Since no PDE is solved for re-distancing, the method does not have stability time step restrictions, which is particularly useful in combination with AMR, used here to efficiently resolve fine interface features. A high-order (implemented up to the 6th-order) level set approach is utilized for a new sharp treatment of mix elements, which reconstructs multiple-per-element solution fields (one for each material present in the mix element). Reconstruction incorporates interfacial jump conditions, which are enforced in the least-squares sense at the interfacial marker positions provided by MRD. Since no explicit differentiation across the interface is involved in the assembly of residuals for mass, momentum and energy equations, the method is capable of capturing discontinuous solutions at multi-material interfaces with high order, and without Gibbs oscillations. [Preview Abstract] |
Sunday, November 20, 2016 8:26AM - 8:39AM |
A12.00003: A Finite Element Method for Simulation of Compressible Cavitating Flows Ehsan Shams, Fan Yang, Yu Zhang, Onkar Sahni, Mark Shephard, Assad Oberai This work focuses on a novel approach for finite element simulations of multi-phase flows which involve evolving interface with phase change. Modeling problems, such as cavitation, requires addressing multiple challenges, including compressibility of the vapor phase, interface physics caused by mass, momentum and energy fluxes. We have developed a mathematically consistent and robust computational approach to address these problems. We use stabilized finite element methods on unstructured meshes to solve for the compressible Navier-Stokes equations. Arbitrary Lagrangian-Eulerian formulation is used to handle the interface motions. Our method uses a mesh adaptation strategy to preserve the quality of the volumetric mesh, while the interface mesh moves along with the interface. % The interface jump conditions are accurately represented using a discontinuous Galerkin method on the conservation laws. Condensation and evaporation rates at the interface are thermodynamically modeled to determine the interface velocity. We will present initial results on bubble cavitation the behavior of an attached cavitation zone in a separated boundary layer. % [Preview Abstract] |
Sunday, November 20, 2016 8:39AM - 8:52AM |
A12.00004: Numerical simulation of particle dynamics at a fluid interface Pengtao Yue Particles straddling a fluid interface exhibit rich dynamics due to the coexistence of moving boundaries, fluid interfaces, and moving contact lines. For instance, as a particle falls onto a liquid surface, it may sink, float, or even bounce off depending on a wide range of parameters. To better understand the dynamics of such a multiphase system, we develop a finite-element based arbitrary Lagrangian-Eulerian-phase-field method. The governing equations for particles and fluids are solved in a unified variational framework that satisfies an energy law. We first validate our code by computing three problems found in literature: sinking of a horizontal cylinder through an air-water interface, sinking of a sphere through an air-oil interface at small Reynolds numbers, and bouncing of a sphere after its normal impact onto an air-water interface. Our numerical results show good agreements with experimental data. We then investigate the effect of wetting properties, including static contact angle, slip length, and wall energy relaxation, on particle dynamics at the fluid interface. [Preview Abstract] |
Sunday, November 20, 2016 8:52AM - 9:05AM |
A12.00005: An inviscid regularization technique for the simulation of compressible multiphase flow Bahman Aboulhasanzadeh, Kamran Mohseni A common feature of flow problems involving shocks, turbulence, and/or two-phase flows is the $k$-infinity irregularity. We present an inviscid regularization technique, dubbed observable regularization, for the simulation of compressible multiphase flows. In this technique, we use the observable divergence theorem to derive the conservation equations considering the observability limit in any computational or physical system. To avoid contamination of the result with numerical diffusion a pseudo-spectral technique is used to discretize the conservation equations. This methodology has been tested successfully for regularizing single-phase problems with shocks and/or turbulence. Using observable Euler equations, shock-bubble and shock-drop interactions are simulated and the results are compared with available experimental data from literature, showing good agreement. Observable equations are capable of simultaneously regularizing problems with shocks, turbulence, and/or sharp interfaces without the need for treating each aspect separately. [Preview Abstract] |
Sunday, November 20, 2016 9:05AM - 9:18AM |
A12.00006: Continuity waves in fully resolved simulations of settling particles Daniel Willen, Adam Sierakowski, Andrea Prosperetti Fully resolved simulations of 500 to 2,000 particles settling in a fluid have been conducted with the Physalis method. A new approach to the reconstruction of pseudo-continuum fields is described and is used to examine the results with the purpose of identifying concentration waves. The velocity of concentration waves is successfully deduced from the simulations. A comparison of the results with continuity wave theory shows good agreement. Several new insights about the particle microstructure conditionally averaged on volume fraction and velocity are also described. [Preview Abstract] |
Sunday, November 20, 2016 9:18AM - 9:31AM |
A12.00007: Physics-Based Preconditioning for the Numerical Solution of the All-Speed Compressible Navier-Stokes Equations with Laser-Induced Phase Change Brian Weston, Robert Nourgaliev, Jean-Pierre Delplanque, Andy Anderson The numerical simulation of flows associated with metal additive manufacturing processes such as selective laser melting and other laser-induced phase change applications present new challenges. Specifically, these flows require a fully compressible formulation since rapid density variations occur due to laser-induced melting and solidification of metal powder. We investigate the preconditioning for a recently developed all-speed compressible Navier-Stokes solver that addresses such challenges. The equations are discretized with a reconstructed Discontinuous Galerkin method and integrated in time with fully implicit discretization schemes. The resulting set of non-linear and linear equations are solved with a robust Newton-Krylov (NK) framework. To enable convergence of the highly ill-conditioned linearized systems, we employ a physics-based operator split preconditioner (PBP), utilizing a robust Schur complement technique. We investigate different options of splitting the physics (field) blocks as well as different block solvers on the reduced preconditioning matrix. We demonstrate that our NK-PBP framework is scalable and converges for high CFL/Fourier numbers on classic problems in fluid dynamics as well as for laser-induced phase change problems. [Preview Abstract] |
Sunday, November 20, 2016 9:31AM - 9:44AM |
A12.00008: Development of multiphase CFD flow solver in OpenFOAM Chad Rollins, Hong Luo, Nam Dinh We are developing a pressure-based multiphase (Eulerian) CFD solver using OpenFOAM with Reynolds-averaged turbulence stress modeling. Our goal is the evaluation and improvement of the current OpenFOAM two-fluid (Eulerian) solver in boiling channels with a motivation to produce a more consistent modeling and numerics treatment. The difficulty lies in the prescense of the many forces and models that are tightly non-linearly coupled in the solver. Therefore, the solver platform will allow not only the modeling, but the tracking as well, of the effects of the individual components (various interfacial forces/heat transfer models) and their interactions. This is essential for the development of a robust and efficient solution method. There has be a lot of work already performed in related areas that generally indicates a lack of robustness of the solution methods. The objective here is therefore to identify and develop remedies for numerical/modeling issues through a systematic approach to verification and validation, taking advantage of the open source nature of OpenFOAM. The presentation will discuss major findings, and suggest strategies for robust and consistent modeling (probably, a more consistent treatment of heat transfer models with two-fluid models in the near-wall cells). [Preview Abstract] |
Sunday, November 20, 2016 9:44AM - 9:57AM |
A12.00009: Numerical Simulation of Compressible Multi-phase flows using HLLC extension of AUSM$+$-up Scheme Gaurav Dhir, Kowsik Bodi Solving Multi-fluid equations has always required an onerous effort from researchers with regards to implementing an appropriate numerical scheme which could capture the various facets of such type of flows along with the interaction between the various phases present. Additionally, multi-phase flows bring with them peculiar mathematical properties such as non-hyperbolicity and non-conservativeness which further increases the complexity involved. Our presentation shall present an insight into the advantages and limitations of several numerical schemes proposed in the past and propose to use the HLLC extension of AUSM$+$-up approach to model such type of flows. We use the single pressure based stratified flow concept and by presenting several test cases, we prove that our method robustly computes multi-phase flow involving discontinuities, such as shock waves and fluid interfaces. Additionally, we present a formulation to incorporate phase transition within multi-fluid equations and establish the validity of this method by presenting several two dimensional test cases such as the Shock-Water Column Interaction problem, the Water-Shock/Air Bubble Interaction problem and the 2D Underwater Explosion problem. [Preview Abstract] |
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