Bulletin of the American Physical Society
63rd Annual Meeting of the APS Division of Fluid Dynamics
Volume 55, Number 16
Sunday–Tuesday, November 21–23, 2010; Long Beach, California
Session GD: CFD I: Immersed Boundary and Interface Methods |
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Chair: Eric Serre, Aix-Marseille Universite Room: Long Beach Convention Center 102B |
Monday, November 22, 2010 8:00AM - 8:13AM |
GD.00001: Effect of Rough Moving Boundaries on Plane Poiseuille Flow David Cotrell, B.J. Alder We report computations of unsteady solutions of the Navier-Stokes equations for flow between two rough plates driven by a stream-wise pressure gradient and time-periodic motion of the boundaries. We consider the flow as a function of the stream-wise pressure gradient for several values of the wall amplitude and computational aspect ratio, and investigate a large range of boundary modulation frequencies. Base flow calculations show that, as expected, for a constant stream-wise pressure gradient and no motion of the boundaries, the flow rate decreases with increasing wall roughness amplitude. On the other hand, if the wall modulation frequency is high enough the flow rate can ultimately surpass the smooth walled case for. This work was performed under the auspices of the Lawrence Livermore National Security, LLC, (LLNS) under Contract No. DE-AC52-07NA27344. [Preview Abstract] |
Monday, November 22, 2010 8:13AM - 8:26AM |
GD.00002: High-Order Finite-Difference Solution of the Poisson Equation with Interface Jump Conditions II Alexandre Marques, Jean-Christophe Nave, Rodolfo Rosales The Poisson equation with jump discontinuities across an interface is of central importance in Computational Fluid Dynamics. In prior work, Marques, Nave, and Rosales have introduced a method to obtain fourth-order accurate solutions for the constant coefficient Poisson problem. Here we present an extension of this method to solve the variable coefficient Poisson problem to fourth-order of accuracy. The extended method is based on local smooth extrapolations of the solution field across the interface. The extrapolation procedure uses a combination of cubic Hermite interpolants and a high-order representation of the interface using the Gradient-Augmented Level-Set technique. This procedure is compatible with the use of standard discretizations for the Laplace operator, and leads to modified linear systems which have the same sparsity pattern as the standard discretizations. As a result, standard Poisson solvers can be used with only minimal modifications. Details of the method and applications will be presented. [Preview Abstract] |
Monday, November 22, 2010 8:26AM - 8:39AM |
GD.00003: A New Method for the Level Set Equation Using a Hierarchical-Gradient Truncation and Remapping Technique Haruhiko Kohno, Jean-Christophe Nave We present a novel numerical method for solving the advection equation for a level set function. The new method uses Hierarchical-Gradient Truncation and Remapping (H-GTaR) of the original PDE. Our strategy reduces the original PDE to a set of decoupled linear ODEs with constant coefficients. Additionally, we introduce a remapping strategy used to periodically guarantee solution accuracy. The resulting scheme is unconditionally stable, and the solution accuracy is nearly independent of the time step. We will evaluate our method in 2D and present results to several classical benchmark problems. [Preview Abstract] |
Monday, November 22, 2010 8:39AM - 8:52AM |
GD.00004: A new compressible and incompressible immersed interface method based on analytic continuation, level sets and smooth extension techniques Hasib Uddin, Richard Kramer, Carlos Pantano We present a new immersed interface methodology for embedded complex geometries in Cartesian fluid solvers. The object boundaries are represented using a standard level set. The flow fields are then extended smoothly inside the fictitious domain, using an improved version of the approach pioneered by Osher and co workers, and the boundary conditions are enforced by a technique inspired by analytic continuation. In the compressible version of the method, each fluid field is extended independently with the only constraints being the boundary conditions associated with that field. In the incompressible version of this method, the divergence-free condition of the velocity field is enforced throughout the fictitious domain in addition to the no-slip boundary condition. Applications to shock reflections, shock-ramp interactions and both supersonic and zero-Mach number flows over several simple, e.g., a sphere, and complex three-dimensional objects will be demonstrated. [Preview Abstract] |
Monday, November 22, 2010 8:52AM - 9:05AM |
GD.00005: Level-set immersed boundary method for simulating 3D turbulent free surface flows in arbitrarily complex open channels Seokkoo Kang, Fotis Sotiropoulos A numerical method is developed for simulating three-dimensional free surface flows in open channels of arbitrarily complex bathymetry. The complex geometry is handled using the curvilinear immersed boundary (CURVIB) method of Ge and Sotiropoulos (J. of Computational Physics, 2007) and free surface deformation is modeled by employing a two-phase flow level-set approach. A new method is developed for solving the level-set equations and the reinitialization equation in the context of the CURVIB framework. The method is validated for various free-surface model problems and its capabilities are demonstrated by applying to simulate turbulent free-surface flow in an open channel with embedded complex hydraulic structures. [Preview Abstract] |
Monday, November 22, 2010 9:05AM - 9:18AM |
GD.00006: The immersed interface method for 3D rigid objects in a flow Sheng Xu In the immersed interface method, an object moving in a fluid is treated as the fluid enclosed by a singular force, and the singular force enters numerical schemes through jump conditions. In this talk, I will present a boundary condition capturing approach to determine the singular force for a 3D moving rigid object. Unlike many \emph{ad hoc} penalty approaches, this approach is explicit but numerically stable. I will demonstrate its accuracy, stability and efficiency using flow due to an oscillating sphere/torus and flow due to a flapping wing. [Preview Abstract] |
Monday, November 22, 2010 9:18AM - 9:31AM |
GD.00007: Optical Flow-Based Modeling and Velocimetry Seth Dillard, James Buchholz, H.S. Udaykumar One of the challenges involved with modeling organisms and other complex systems using CFD simulations lies in describing their complex geometries and motions with fidelity. We have developed a framework to overcome this difficulty by employing imagery as a basis from which to directly create such models. By combining nonlinear optical flow with image segmentation techniques, we are able to generate a level set field that moves under the influence of optical flow vectors computed on an image sequence, and thereby supply an immersed boundary to our flow solver. All of these operations take place on a fixed Cartesian mesh, obviating the complexities associated with fitted grid methods. These methodologies can also be applied to experimental flow velocimetry, and offer significantly enhanced spatial resolution compared with correlation methods used in particle image velocimetry. Preliminary application of the nonlinear optical flow methodology to planar fluid flow measurements will be demonstrated. [Preview Abstract] |
Monday, November 22, 2010 9:31AM - 9:44AM |
GD.00008: The Immersed Interface Method for Two-Fluid Flows Miguel Uh In the Immersed Interface Method, a two-fluid flow problem is formulated as one set of governing equations and simulated on a fixed Cartesian grid. The effect of the two- fluid interface enters the formulation as a singular force and a numerical scheme as jump conditions. In this talk, we will present principal jump conditions and discuss the difficulties in implementing them. Finally, we will demonstrate the accuracy and efficiency of our immersed interface method for two-fluid flow simulation. [Preview Abstract] |
Monday, November 22, 2010 9:44AM - 9:57AM |
GD.00009: A Direct-Forcing Immersed Boundary Method with Dynamic Velocity Interpolation Randall McDermott In a direct-forcing immersed boundary method, first introduced by Fadlun et al. (2000), the momentum equation is supplemented by a force term which drives the local velocity to a specified value. The method has gained popularity due to its ease of implementation in Cartesian, structured flow solvers and several variants on the basic theme have been proposed (see, e.g., Balaras (2004), Choi and Edwards (2008), Roman et al. (2009)). Generally, the first off-wall velocity point is forced to obey a simple interpolation, usually a linear, power-law, or log-law profile. These methods have been shown to work well for incompressible, statistically stationary flows. In the method proposed here, the velocity is obtained through dynamic evaluation of the boundary layer equations. The advantage of this approach is that, in principle, it is possible to better control the flow divergence (important for variable-density flows like fire--the primary application of our solver) and to account for the effects of local fluctuations in the flow field. The boundary layer equations are discretized with a second-order spatial scheme and time-step restrictions are avoided by formulating the streamwise momentum equation as an ordinary differential equation in time with a simple analytical solution. The method is tested on wavy-channel and cylinder/sphere wake flows across a broad range of Reynolds numbers. [Preview Abstract] |
Monday, November 22, 2010 9:57AM - 10:10AM |
GD.00010: A new immersed interface method applied to hydrodynamics of a fusion chamber Richard Kramer, Carlos Pantano, Gwen Loosmore, Andrew Cook A new immersed interface technique is discussed for a high-order Cartesian fluid solver, with results presented from a range of problems. The new approach is designed to generate smooth fields in the ghost (fictitious) regions of the domain occupied by solid objects. A parallel implementation of this approach and its coupling to very complex geometries is discussed. We discuss some preliminary results for jet cooling inside a chamber containing Xenon at temperatures around 8000 K. The compressible, turbulent and radiative environment is modeled using the LLNL code Miranda with the new immersed interface technique used to represent the chamber walls. [Preview Abstract] |
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