Bulletin of the American Physical Society
65th Annual Meeting of the APS Division of Fluid Dynamics
Volume 57, Number 17
Sunday–Tuesday, November 18–20, 2012; San Diego, California
Session A5: Computational Fluid Dynamics I |
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Chair: Gianluca Iaccarino, Stanford University Room: 24A |
Sunday, November 18, 2012 8:00AM - 8:13AM |
A5.00001: An Improved Advection Scheme for Implicit Interfaces on Cartesian Grids Zhipeng Qin, Keegan Delaney, Amir Riaz, Elias Balaras Existing methods for the advection of implicit interfaces on Cartesian grids employ a reconfiguration of the contours of the phase function in the neighborhood of the interface to facilitate the implementation of interfacial jump conditions. This is achieved with either the classical redistance techniques, within the context of the level set approach, or the more recent interface recompression methods that attempt to maintain interface width during advection. While the latter approach performs much better with respect to mass conservation we show that the associated interface topology suffers as a result. A new approach is presented to recreate interface topology in the neighborhood of the interface based on local curvature smoothing. With the help of canonical examples the approach is shown to both conserve mass and maintain topology during advection. [Preview Abstract] |
Sunday, November 18, 2012 8:13AM - 8:26AM |
A5.00002: The immersed interface method for simulating two-fluid flows Sheng Xu, Miguel Uh In this talk, we present a second-order accurate implementation of the immersed interface method for computing a two-fluid flow. In the method, jump conditions in the flow fields caused by the effect of the two-fluid interface and the discontinuous fluid properties are incorporated into a numerical scheme on a Cartesian grid. We discuss how to derive and use these jump conditions to achieve second-order accuracy. We test the accuracy, efficiency and stability of our implementation on some canonical two-fluid flows. [Preview Abstract] |
Sunday, November 18, 2012 8:26AM - 8:39AM |
A5.00003: Interface-tracking using a compressive advection method and a compositional modelling approach Dimitrios Pavlidis, Jefferson Gomes, Christopher Pain, Omar Matar We describe progress on a consistent approach for interface- tracking in which each component, representing a different phase/fluid, has a sum of unity. Our aim is to develop a general multiphase modelling approach based on fully-unstructured meshes that can exploit the latest mesh adaptivity methods, and in which each fluid phase may have a number of components that are assumed to be immiscible in this work although not a requirement of the approach. The method is based on a new mixed finite element pair, the P1DG-P2 element, in which pressure has a quadratic variation and velocity a discontinuous linear variation with the discontinuity between elements. This element allows us to represent key balances such as hydrostatic balance exactly assuming a linear variation in buoyancy. This means that on unstructured meshes we do not have problems representing these key balances that can result in large pressure gradients which, in turn, generate large spurious velocities that can dominate the solution. We apply the method to a series of benchmark problems that demonstrate the approach and show that the method works for at least three different fluids, and that it avoids putting a priority on resolving any of these fields or components. [Preview Abstract] |
Sunday, November 18, 2012 8:39AM - 8:52AM |
A5.00004: Interface-tracking electro-hydrodynamic model for droplet coalescence Lindsay Crowl Erickson, David Noble Many fluid-based technologies rely on electrical fields to control the motion of droplets, e.g. micro-fluidic devices for high-speed droplet sorting, solution separation for chemical detectors, and purification of biodiesel fuel. Precise control over droplets is crucial to these applications. However, electric fields can induce complex and unpredictable fluid dynamics. Recent experiments (Ristenpart et al. 2009) have demonstrated that oppositely charged droplets bounce rather than coalesce in the presence of strong electric fields. Analytic hydrodynamic approximations for interfaces become invalid near coalescence, and therefore detailed numerical simulations are necessary. We present a conformal decomposition finite element (CDFEM) interface-tracking method for two-phase flow to demonstrate electro-coalescence. CDFEM is a sharp interface method that decomposes elements along fluid-fluid boundaries and uses a level set function to represent the interface. The electro-hydrodynamic equations solved allow for convection of charge and charge accumulation at the interface, both of which may be important factors for the pinch-off dynamics in this parameter regime. [Preview Abstract] |
Sunday, November 18, 2012 8:52AM - 9:05AM |
A5.00005: Numerical simulation in 3D of atomizing coaxial gas-liquid jets Gilou Agbaglah, Daniel Fuster, Geordie McBain, Stephane Popinet, Stephane Zaleski We investigate three-dimensional multiphase flows using the Volume of Fluid method. We are in particular focusing on the problem of jet atomizaton. We use a Volume of Fluid method with oct-tree adaptive finite volume discretization, mostly using the Gerris free code. Surface tension is computed by a balanced-force method. Coaxial, 3D, round and planar air-water jets similar to those investigated experimentally are studied and compared to the equivalent jets in 2D axisymetric and 2D planar setups. A mechanism for large-scale jet disruption is observed. The distribution of droplet sizes is compared to experimental measurements. The effect of grid resolution and of the presence of an explicitly modelled solid separator plate is discussed. [Preview Abstract] |
Sunday, November 18, 2012 9:05AM - 9:18AM |
A5.00006: An Optimization-Based Lagrangian Particle Method for Navier-Stokes Paul Covington, Frank Ham, Parviz Moin Particle methods have recently experienced renewed interest due to their ability to more naturally handle material advection for multiphysics applications as well as complex moving boundaries. Most methods, however, lack a systematic treatment of formal accuracy. This study aims to provide a general framework for constructing Lagrangian methods that obey a bilinear form. Basis functions are defined independent of a traditional computational grid by borrowing concepts from convex optimization. The method is applied to the compressible Navier-Stokes equations and two-phase problems. Results will be presented with emphasis placed on problems with analytical solutions such as a convecting Euler vortex. Accuracy will be compared to an extensively validated Eulerian finite volume code. The applicability to 3D problems of practical interest will also be discussed with respect to algorithmic considerations and computational cost. [Preview Abstract] |
Sunday, November 18, 2012 9:18AM - 9:31AM |
A5.00007: Particle Gradient-Augmented Level Set in Multiphase Flow Problems Olivier Mercier, Jean-Christophe Nave, Rodolfo Ruben Rosales, Benjamin Seibold The goal of this presentation is to present the particle gradient-augmented level set method in the context of multiphase flows. Specifically, we will show how topological changes can be taken into account by a modification of the original method. Finally, we will present applications to multi-phase Navier-Stokes by combining it with the ghost fluid method. [Preview Abstract] |
Sunday, November 18, 2012 9:31AM - 9:44AM |
A5.00008: Langrangian Coherent Structure Visualizations in High-Resolution DNS Daniel Nelson Lagrangian coherent structures have become an important addition to flow visualization and analysis of turbulent flow topology and separated flow. The identification of zero-mass flux material surfaces is shedding new light on flow transport phenomena. We discuss a high-order resolution determination of the Lagrangian coherent structures. In direct numerical simulation based on higher-order discontinuous Galerkin method, finite time Lyapunov exponents are determined on-the-fly in forward and backward-time based on spectral operators. A higher-order time integrator traces fluid particles that are initialized at quadrature points. Lagrangian coherent structures are visualized in a range of flows including a shear layer, convected vortex and bluff body wakes. [Preview Abstract] |
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