Bulletin of the American Physical Society
67th Annual Meeting of the APS Division of Fluid Dynamics
Volume 59, Number 20
Sunday–Tuesday, November 23–25, 2014; San Francisco, California
Session R33: Computational Methods and Modeling of Multiphase Flows II |
Hide Abstracts |
Chair: Olivier Desjardins, Cornell University Room: 2022 |
Tuesday, November 25, 2014 1:05PM - 1:18PM |
R33.00001: Numerical study of Taylor bubbles with adaptive unstructured meshes Zhihua Xie, Dimitrios Pavlidis, James Percival, Chris Pain, Omar Matar, Abbas Hasan, Barry Azzopardi The Taylor bubble is a single long bubble which nearly fills the entire cross section of a liquid-filled circular tube. This type of bubble flow regime often occurs in gas-liquid slug flows in many industrial applications, including oil-and-gas production, chemical and nuclear reactors, and heat exchangers. The objective of this study is to investigate the fluid dynamics of Taylor bubbles rising in a vertical pipe filled with oils of extremely high viscosity (mimicking the ``heavy oils'' found in the oil-and-gas industry). A modelling and simulation framework is presented here which can modify and adapt anisotropic unstructured meshes to better represent the underlying physics of bubble rise and reduce the computational effort without sacrificing accuracy. The numerical framework consists of a mixed control-volume and finite-element formulation, a ``volume of fluid''-type method for the interface capturing based on a compressive control volume advection method, and a force-balanced algorithm for the surface tension implementation. Numerical examples of some benchmark tests and the dynamics of Taylor bubbles are presented to show the capability of this method. [Preview Abstract] |
Tuesday, November 25, 2014 1:18PM - 1:31PM |
R33.00002: Modeling Multi-Phase Flow using Fluctuating Hydrodynamics Anuj Chaudhri, John Bell, Alejandro Garcia, Aleksandar Donev Incorporating thermal fluctuations in continuum Navier-Stokes equations requires the development of numerical methods that solve the complex stochastic partial differential equations of fluctuating hydrodynamics. The situation becomes more complex when more than one fluid phase is involved as in a liquid-vapor system. We describe a stochastic method of lines discretization of the fully compressible Landau-Lifshitz-Navier-Stokes equations with the van der Waals equation of state. The diffuse interface method is used to model the order parameter (density) across the interface with the surface tension effects giving rise to Korteweg type stresses in the momentum and energy equations. The numerical scheme is validated by comparison of measured structure factors and capillary wave spectra with equilibrium theory. We also present several non-equilibrium examples to illustrate the capability of the algorithm to model multi-phase fluid phenomena in a neighborhood of the critical point. These examples include a study of the impact of fluctuations on the spinodal decomposition following a rapid quench, as well as the piston effect in a cavity with supercooled walls. The conclusion in both cases is that thermal fluctuations affect the size and growth of the domains in off-critical quenches. [Preview Abstract] |
Tuesday, November 25, 2014 1:31PM - 1:44PM |
R33.00003: A hierarchy of two-fluid models with specific numerical methods for the simulation of bubbly flows/acoustic interactions Florence Drui, Adam Larat, Vincent Le Chenadec, Samuel Kokh, Marc Massot Simulating the injection, evaporation, and combustion of fuel in energy conversion applications represents a major challenge. The formulation of closed sets of equations able to accurately predict these complex systems by relying solely on averaged information has been a longstanding problem. As a consequence, no simple model is currently available that describes the complete injection process, known to range from the separated phase regime in the early stages of atomization to the dispersed regime that occurs further downstream. The benefits of such a unified formulation would be significant, both in terms of computational cost and algorithmic complexity. In order to identify the challenges in formulating one such approach, a one-pressure, one-velocity isothermal two-fluid model for bubble-acoustic wave interaction is studied and incrementally improved by introducing additional variables that characterize the micro-structure of bubbles. The elastic and dissipative structures of the models are investigated in depth, and their performances compared to reference solutions (Drew \& Passman, 1999). Numerical strategies are devised which can accurately handle the whole hierarchy and related stiffness, and rely on Suliciu's relaxation method as well as an asymptotic-preserving treatmen [Preview Abstract] |
Tuesday, November 25, 2014 1:44PM - 1:57PM |
R33.00004: High Performance Computing for complex fluids simulation Mourad Ismail, Vincent Chabannes, Vincent Doyeux, St\'ephane Priem, Christophe Prud'homme In order to better understand the behavior of complex fluids in general and blood flow in particular, several models have been proposed by considering blood as a Newtonian fluid (governed by the Stokes equations or Navier-Stokes) in which are immersed deformable entities. These particles contain a second fluid of different viscosity and density from outer fluid. This context, I will present some models based on the same principle and will show its validations using some known benchmarks. I will also talk briefly about High Performance Computing in the framework of complex fluids simulations. [Preview Abstract] |
Tuesday, November 25, 2014 1:57PM - 2:10PM |
R33.00005: Probability Density Function Analysis of Turbulent Condensation Using GPU Hardware Ryan Keedy, James Riley, Alberto Aliseda Growth of liquid droplets by condensation is an important phenomenon in many environmental and industrial applications. In a homogenous, supersaturated environment, condensation will tend to narrow the diameter distribution of a poly-disperse collection of droplets. However, free shear turbulence can broaden the diameter distribution due to intermittency in the mixing and by subjecting droplets to non-Gaussian supersaturation statistics. In order to understand the condensation behavior of water droplets in a turbulent flow, it is necessary to understand the dispersion of the droplets and transported scalars. We describe a hybrid approach for predicting droplet growth and dispersion in a turbulent mixing layer and compare our computational predictions to experimental data. The approach utilizes a finite-volume code to calculate the fluid velocity field and a particle-mesh Monte Carlo method to track the locations and thermodynamics of the large number of stochastic particles throughout the domain required to resolve the Probability Density Function of the water vapor and droplets. The particle tracking algorithm is designed to take advantage of the computational power of a large number of GPU cores, with significant speed-up when compared against a baseline CPU configuration. [Preview Abstract] |
Tuesday, November 25, 2014 2:10PM - 2:23PM |
R33.00006: Simulation of the evolution of a condensing aerosol in homogeneous isotropic turbulence Amjad Alshaarawi, Antonio Attili, Fabrizio Bisetti The nucleation, growth, and coagulation of liquid droplets in three-dimensional homogeneous isotropic turbulence at Re$_{\lambda} \approx 150$ is simulated. Patches of dry and cold gas mix with patches of hot carrier gas saturated with vapor of a condensable species, inducing the homogeneous nucleation of particles due to supersaturation. The simulation consists of a three-dimensional direct numerical simulation of homogeneous isotropic turbulence with a statistically stationary forced velocity field. All length and time scales of fluid motion and scalar mixing are resolved adequately. A model based on the quadrature method of moments and Lagrangian transport of the moments is adopted for the transport and dynamics of the liquid droplets. Our results show that droplets form early in the evolution of the flow field and their concentration peaks on the cold side of the mixing layers separating the patches of hot and cold gas, where droplets nucleate most intensely. Conversely, the droplets grow most rapidly on the hot side of the mixing layers. As turbulent mixing displaces the droplets into regions of hot and moist gas, the droplets' size increases markedly. Conditional statistics of the aerosol phase in the mixture fraction space are employed to investigate this trend. [Preview Abstract] |
Tuesday, November 25, 2014 2:23PM - 2:36PM |
R33.00007: Characteristics-based sectional modeling of aerosol nucleation, condensation and transport Edo Frederix, Arkadiusz Kuczaj, Markus Nordlund, Milos Stanic, Bernard Geurts Aerosols can be generated by physical processes such as nucleation, condensation and coalescence. To predict spatially varying statistical properties of such aerosols, e.g., the size distribution of the droplets, these processes must be captured accurately. We model nucleation using classical nucleation theory, whereas the condensational growth is captured with a molecular diffusivity model. The droplet size distribution is discretized using a sectional approach, in which droplets are characterized in terms of a number of fixed droplet size bins. Often, in such a formulation, the numerical time step restrictions arising from condensation and nucleation are more pronounced than those of the corresponding fluid flow, thereby significantly limiting the global time step size. We propose a moment-conserving method in which this limitation is avoided, by utilizing the analytical solutions of the spatially homogeneous nucleation-condensation subproblem. The method is validated against experimental and numerical data of a laminar flow diffusion chamber, and shows an excellent agreement while being restricted only by a flow-related time step criterion. The research presented in this work was financially supported by Philip Morris Products S.A. [Preview Abstract] |
Tuesday, November 25, 2014 2:36PM - 2:49PM |
R33.00008: A Molecular Dynamics Simulation of the Density Fluctuation of Diatomic Fluids around the Critical Point Shohei Ikawa, Takashi Tokumasu, Nobuyuki Tsuboi, Hiroki Nagashima, Shin-ichi Tsuda In this study, we evaluated the density fluctuation of diatomic fluids around the critical point. We simulated the density fluctuation of 2-Center-Lennard-Jones (2CLJ) fluids, which have molecular elongations as one of the parameters, by Molecular Dynamics (MD) method. We focused on the effect of anisotropy of diatomic fluid on fluctuation structure to evaluate the principle of corresponding state of the density fluctuation. As the evaluation methods, we calculated the dispersion of number of molecules at certain domain and also computed static structure factor. We calculated those values of diatomic fluids which have various molecular elongations to compare the difference of fluctuation structure of fluids. As results, the principle of corresponding state is satisfied because there is no significant difference in the fluctuation structure between fluids which have shorter molecular elongation and longer one. Hereafter, we are going to calculate the intermediate scattering function and dynamic structure factor to evaluate the principle of corresponding state of the density fluctuation in detail. [Preview Abstract] |
Tuesday, November 25, 2014 2:49PM - 3:02PM |
R33.00009: Strategies for the analysis of complex interface topologies in turbulent two-phase flows Vincent Le Chenadec, Shahab Mirjalili, Milad Mortazavi, Ali Mani Two-phase flows of immiscible fluids occur in a wide range of phenomena encountered in environmental sciences and engineering; the interest in their prediction is therefore significant. The continuous development of High-Performance Computing technologies, and the level of predictivity reached by the numerical solvers, enable increasingly complex configurations to be tackled. This has therefore spurred the development of numerical algorithms able to carry first principle simulations of complex interfacial flows. Recent developments have highlighted the benefits of first-principle discretizations in providing accurate solutions of the underlying stiff partial differential equations. In particular, the challenge posed by the presence of an interface has been shown to be effectively addressed by a new generation of geometric Volume-of-Fluid methods, with enhanced flexibility over more traditional one-dimensional schemes. The aim of this work is to extend these capabilities to address two aspects: the statistical analysis of surfaces in complex two-phase flows, and the coupling of first-principle solvers with subgrid-scale models. [Preview Abstract] |
Tuesday, November 25, 2014 3:02PM - 3:15PM |
R33.00010: Simulations of flow focused at the interface of free flowing fluid and porous media Mac Panah, Francois Blanchette We present a novel numerical approach to simulate flow in and adjacent to porous media, with applications to geological flows. Rivers, flood water, and turbidity currents all involve water flowing over and within sandy deposits, leading to erosion or deposition of sand grains. This process is simulated using a continuum approach (Navier-Stokes and Brinkman equations) with a sharp interface between porous media and unimpeded flow. Our numerical solver allows this interface to be mobile and therefore can handle the dynamically evolving geometries present in these applications. We validated our numerical method by computing drag coefficients on 2D porous cylinders as a function of Reynolds and Darcy numbers. We then studied the flow generated within a deposit by an external fluid flow, and deduced erosion rates in sand beds. In a broader application, this mixed solver can be used to capture details in erosive regions, and its results may be incorporated into a coarser Navier-Stokes solver applied over larger scales. [Preview Abstract] |
Tuesday, November 25, 2014 3:15PM - 3:28PM |
R33.00011: ABSTRACT WITHDRAWN |
Tuesday, November 25, 2014 3:28PM - 3:41PM |
R33.00012: Significance of chamber pressure to complex multi-phase physics in jet engine fuel injection processes Rainer Dahms, Joseph Oefelein Injection processes in jet engines at chamber pressures in excess of the thermodynamic critical pressure of the liquid fuel are not well understood. Under some conditions, a distinct two-phase interface may not exist anymore which eliminates the presence of classical spray atomization phenomena. A comprehensive model for jet engine fuel injections is derived to quantify the conditions under which the interfacial dynamics transition to diffusion-dominated mixing processes without surface tension. At certain conditions, the model shows two-phase interfaces with substantially increased thicknesses and distinctively reduced mean free paths in comparison to ambient pressure conditions. Then, the underlying assumptions of a distinct two-phase interface do not apply anymore and the interface along with its surface tension is shown to deteriorate as it broadens substantially. As a consequence of this physical complexity, the conceptual view of spray atomization and evaporation as an appropriate model for jet engine injection processes is, contrary to conventional wisdom, questionable at certain operating conditions. Instead, a Large Eddy Simulation using a dense-fluid approximation is applied which takes the complex thermo-physics of real-fluid behavior into account. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700