Bulletin of the American Physical Society
66th Annual Meeting of the APS Division of Fluid Dynamics
Volume 58, Number 18
Sunday–Tuesday, November 24–26, 2013; Pittsburgh, Pennsylvania
Session A5: CFD I: Immersed Boundary Methods |
Hide Abstracts |
Chair: Shen Xu, Southern Methodist University Room: 327 |
Sunday, November 24, 2013 8:00AM - 8:13AM |
A5.00001: A sharp, robust, and conservative geometric immersed boundary technique for moving boundaries Peter Brady, Olivier Desjardins, Perrine Pepiot Simulation of solid-fluid systems with complex moving boundaries can be greatly simplified using immersed boundary (IB) methods. IB methods allow for the representation of complex geometries on simple (i.e., Cartesian) meshes, providing an alternative to using a full body-fitted mesh, which often requires an unstructured CFD code and a costly grid-regeneration procedure at every time step. However, using a non body-fitted mesh with IB creates new challenges, including insufficient accuracy in the application of boundary conditions and the potential lack of conservation properties. These challenges are further exacerbated when considering a moving IB. Using a cut-cell IB approach, where the cells that intersect with the solid body are cut such that they become body-fitted, allows for a sharp, discretely conservative IB treatment. With moving geometries, sharp IB methods tend to lack robustness due to the ``fresh-cell/dead-cell'' problem - the addition or removal of fluid control volumes from the mesh. Rather than relying on an interpolation/smoothing operation to address this issue, a novel semi-Lagrangian geometric transport scheme is used. This fully conservative treatment is verified using the method of manufactured solutions and validated with several complex flows. [Preview Abstract] |
Sunday, November 24, 2013 8:13AM - 8:26AM |
A5.00002: Derivation of jump conditions for the immersed interface method with a triangular mesh of an interface Glen Pearson, Sheng Xu The immersed interface method is an accurate and efficient Cartesian grid method for solving interface problems. The key idea of the method is to incorporate necessary interface-induced jump conditions into numerical schemes. In this talk, we present an approach to derive the necessary Cartesian jump conditions for the immersed interface method to solve Poisson equations subject to sharp interfaces in 3D. The approach is based on triangular mesh representation of an interface and can easily handle a non-smooth complex interface. We test this approach on Poisson problems with sharp interfaces shaped as spheres, cubes, cylinders and cones. Our results demonstrate second-order accuracy in the infinity norm. [Preview Abstract] |
Sunday, November 24, 2013 8:26AM - 8:39AM |
A5.00003: The immersed interface method for fluid-solid interaction with boundary condition capturing on triangular meshes Sheng Xu In the immersed interface method, the effect of a rigid solid moving in a fluid is represented as jump conditions incorporated into the discretization of the flow governing equations on a fixed Cartesian grid. In this talk, I present a strategy to numerically compute the required jump conditions toward boundary condition capturing on triangular meshes for solid surfaces. I focus on how to invert a surface gradient operator using a triangular surface mesh to obtain the jump condition of the pressure with desired accuracy. With the boundary condition capturing on triangular surface meshes, the immersed interface method can treat non-smooth solid surfaces. Last, I provide numerical tests to demonstrate the accuracy, efficiency and robustness of the method. [Preview Abstract] |
Sunday, November 24, 2013 8:39AM - 8:52AM |
A5.00004: Model order reduction of embedded boundary models Maciej Balajewicz, Charbel Farhat Embedded boundary methods for Computational Fluid Dynamics (CFD) and fluid-structure interaction problems are gaining popularity because they alleviate computational challenges associated with meshing and large wall boundary motions, deformations, and even topological changes. Developing model order reduction methods for computational frameworks based on the embedded boundary method seems however to be challenging. Indeed, most popular model reduction techniques are projection-based and rely on the computation of fluid basis functions based on simulation snapshots. In a traditional body-fitted computational framework, this computation is straightforward because the fluid always occupies the same computational domain. In the embedded computational framework however, deriving global fluid basis functions is problematic a priori because the Eulerian fluid mesh is traversed by the Lagrangian structural mesh. Hence, snapshots collected at different time-instances lose in this case a sense of coherency or consistency. Nevertheless, we demonstrate that this loss of coherency is not a show-stopper for projection-based model reduction based on snapshots. [Preview Abstract] |
Sunday, November 24, 2013 8:52AM - 9:05AM |
A5.00005: Direct Numerical Simulations of Solid-Fluid Flows Using a Variant of immersed boundary method in Gerris Pei Shui, Prashant Valluri, St\'ephane Popinet A novel 3D Immersed Boundary Method simulating fully coupled fluid-solid interaction with 6 degrees-of-freedom (6DOF) movement has been developed under the aegis of the GERRIS code. Any number of fully immersed solids with complex shapes can be considered. A repulsive force which is the sum of all short-range interactions accounts for collisions and ensures that the solids and the wall do not intersect. The solid-fluid solver has been validated against a series of benchmark cases at a wide range of solid Reynolds numbers (0.1 1000) including that of Jeffrey's orbits. In addition, strong hydrodynamic interaction is seen between multiple solids placed in shear flow. The interaction force is being calibrated as a function of relative distance between the solids, drag and lift forces and will be presented in the conference. In the inertial regime, the problem of migrating dense spheres under Poiseuille flow has been quantitatively validated against simulation results and experiments of Yu et al (2004). There are however some minor divergences in results for migration of neutrally buoyant spheres, but are in full quantitative agreement with experiments of Jeffrey (1989). [Preview Abstract] |
Sunday, November 24, 2013 9:05AM - 9:18AM |
A5.00006: An efficient boundary condition enforced-immersed boundary method for thermal flows with heat flux condition Weiwei Ren, Chang Shu, Wenming Yang, Yu Chen An efficient boundary condition enforced-immersed boundary method (IBM) is proposed in this work for thermal flows involving complex geometries. By treating the heated immersed boundary as a series of heat sources/sinks, Peskin's original IBM has been extended to heat transfer problems with Neumann condition (heat flux) for the temperature field. The main feature of the present approach is to accurately satisfy the energy equation and its boundary conditions through a heat flux correction procedure, which is performed by introducing a heat source/sink term into the energy equation. The heat source/sink is evaluated from the offset boundary heat flux, which is generated from the difference between the normal temperature derivative in the given Neumann condition and the calculated derivative when the boundary effect is not considered. The present solver has proven to be of second order accuracy through a numerical analysis. Its capability and efficiency have also been validated by applying it to numerical examples like forced convection over a stationary heated circular cylinder and natural convection in a horizontal concentric and eccentric annulus between two circular cylinders, from which good agreements with the established data have been achieved. [Preview Abstract] |
Sunday, November 24, 2013 9:18AM - 9:31AM |
A5.00007: An Immersed Boundary-Lattice Boltzmann Method for Simulating Particulate Flows Baili Zhang, Ming Cheng, Jing Lou A two-dimensional momentum exchange-based immersed boundary-lattice Boltzmann method developed by X.D. Niu et al (2006) has been extended in three-dimensions for solving fluid-particles interaction problems. This method combines the most desirable features of the lattice Boltzmann method and the immersed boundary method by using a regular Eulerian mesh for the flow domain and a Lagrangian mesh for the moving particles in the flow field. The non-slip boundary conditions for the fluid and the particles are enforced by adding a force density term into the lattice Boltzmann equation, and the forcing term is simply calculated by the momentum exchange of the boundary particle density distribution functions, which are interpolated by the Lagrangian polynomials from the underlying Eulerian mesh. This method preserves the advantages of lattice Boltzmann method in tracking a group of particles and, at the same time, provides an alternative approach to treat solid-fluid boundary conditions. Numerical validations show that the present method is very accurate and efficient. The present method will be further developed to simulate more complex problems with particle deformation, particle-bubble and particle-droplet interactions. [Preview Abstract] |
Sunday, November 24, 2013 9:31AM - 9:44AM |
A5.00008: Algorithmic improvements for accurate force prediction in diffusive-interface direct-forcing immersed boundary method Xing Zhang, Xiaojue Zhu, Guowei He We detail some algorithmic modifications to the diffusive-interface direct-forcing immersed boundary method of Ulhmann (JCP 209(2005) 448-476). The prediction of local hydrodynamic force can be improved by the following two measures taken. First, by using a ``force correction'' strategy, the fluid penetration near the immersed boundary is significantly reduced. However, the ``force correction'' method also leads to large spurious oscillation in the Lagrangian force. This is problematic since the Lagrangian force also represents the local hydrodynamic surface force in some fluid-structure-interaction (FSI) simulations. By perform an additional filtering (smoothing) step to the Lagrangian force, it is found that the oscillation can be largely suppressed. Accurate prediction of local surface force by the proposed method is demonstrated using the case of 2D flow over a circular cylinder. [Preview Abstract] |
Sunday, November 24, 2013 9:44AM - 9:57AM |
A5.00009: An implicit immersed boundary method for moving body problems in curvilinear coordinates Laura Nicolaou, Seo Yoon Jung, Tamer Zaki A robust immersed boundary method for flow in complex geometries is presented. No-slip conditions are enforced via momentum forcing and mass conservation at the immersed boundary is satisfied via a mass source term developed for moving bodies. Stability is shown to depend on the temporal discretization of the momentum forcing, as inconsistencies between the forcing and the intermediate velocity equations introduce errors near the boundary. An iterative method to compute the forcing term implicitly is proposed, which reduces the errors at the boundary and enhances stability. The convergence of the iterative method, second-order accuracy and enhanced stability of the scheme are demonstrated in a number of test cases. In addition, the proposed mass source term accurately accounts for the movement of the boundary, and reduces the spurious force oscillations which arise in IB simulations of moving body problems. The method is developed for use in a generalised curvilinear system, which lends itself to a wide range of complex flow problems. [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