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 M27: CFD: Immersed Boundary Methods |
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Chair: Amneet Pal Singh Bhalla, University of North Carolina, Chapel Hill Room: E147-148 |
Tuesday, November 22, 2016 8:00AM - 8:13AM |
M27.00001: Immersed boundary peridynamics (IB/PD) method to simulate aortic dissection Amneet Pal Singh Bhalla, Boyce Griffith Aortic dissection occurs when an intimal tear in the aortic wall propagates into the media to form a false lumen within the vessel wall. Rupture of the false lumen and collapse of the true lumen both carry a high risk of morbidity and mortality. Surgical treatment consists of either replacement of a portion of the aorta, or stent implantation to cover the affected segment. Both approaches carry significant risks: open surgical intervention is highly invasive, whereas stents can be challenging to implant and offer unclear long-term patient outcomes. It is also difficult to time optimally the intervention to ensure that the benefits of treatment outweigh its risks. In this work we develop innovative fluid-structure interaction (FSI) model combining elements from immersed boundary (IB) and peridynamics (PD) methods to simulate tears in membranes. The new approach is termed as IB/PD method. We use non-ordinary state based PD to represent material hyperelasticity. Several test problems are taken to validate peridynamics approach to model structural dynamics, with and without accounting for failure in the structures. FSI simulations using IB/PD method are compared with immersed finite element method (IB/FE) to validate the new hybrid approach. [Preview Abstract] |
Tuesday, November 22, 2016 8:13AM - 8:26AM |
M27.00002: A stencil penalty method for improving accuracy of constraint immersed boundary method Rahul Bale, Niclas Jansson, Keiji Onishi, Makoto Tsubokura, Neelesh Patankar The constraint based immersed boundary (cIB) method is known to be accurate for low and moderate Reynolds number (Re) flows. At high Re, we found that cIB is not able produce accurate results. High Re flows typically result in large pressure gradient across fluid-IB interface. This is especially pronounced when the IB is an interface with "zero-thickness." There is also a jump in pressure which leads to incorrect evaluation of pressure gradients near the fluid-IB interface. This error leads to inaccuracies in the boundary layer around the IB and can also lead to leakage of flow across the interface. We propose a novel IB formulation with a modified pressure gradient operator that calculates one-sided gradients on either side of the interface. This removes spurious gradients in pressure across the interface. The pressure gradient operator is modified using a WENO based stencil penalization scheme. [Preview Abstract] |
Tuesday, November 22, 2016 8:26AM - 8:39AM |
M27.00003: A high-order Immersed Boundary method for the simulation of polymeric flow. David Stein, Becca Thomases, Robert Guy We present a robust, flexible, and high-order Immersed Boundary method for simulating fluid flow, including the Incompressible Navier-Stokes equations and certain models of viscoelastic flow, e.g. the Stokes-Oldroyd-B equations. The solution to the PDE is coupled with an equation for a smooth extension of the unknown solution; high-order accuracy is a natural consequence of this additional global regularity. Low and zero Reynolds number problems are handled efficiently and accurately. We demonstrate pointwise convergence of the polymeric stress for flows in complex domains, in contrast to the standard Immersed Boundary method, which generates large errors in the polymeric stress near to the boundaries. [Preview Abstract] |
Tuesday, November 22, 2016 8:39AM - 8:52AM |
M27.00004: An efficient strongly coupled immersed boundary method for deforming bodies Andres Goza, Tim Colonius Immersed boundary methods treat the fluid and immersed solid with separate domains. As a result, a nonlinear interface constraint must be satisfied when these methods are applied to flow-structure interaction problems. This typically results in a large nonlinear system of equations that is difficult to solve efficiently. Often, this system is solved with a block Gauss-Seidel procedure, which is easy to implement but can require many iterations to converge for small solid-to-fluid mass ratios. Alternatively, a Newton-Raphson procedure can be used to solve the nonlinear system. This typically leads to convergence in a small number of iterations for arbitrary mass ratios, but involves the use of large Jacobian matrices. We present an immersed boundary formulation that, like the Newton-Raphson approach, uses a linearization of the system to perform iterations. It therefore inherits the same favorable convergence behavior. However, we avoid large Jacobian matrices by using a block LU factorization of the linearized system. We derive our method for general deforming surfaces and perform verification on 2D test problems of flow past beams. These test problems involve large amplitude flapping and a wide range of mass ratios. [Preview Abstract] |
Tuesday, November 22, 2016 8:52AM - 9:05AM |
M27.00005: The parallelizationn of the immersed interface method for flow around moving rigid objects Sheng Xu To simulate flow around moving objects, the immersed interface method treats the objects as the fluid and recovers their effect on the surrounding flow by incorporating jump conditions across the surfaces of the objects into numerical schemes. In this talk, I will present some recent enhancement of the method toward its parallelization for flow around a large number of rigid objects of complex geometries in 3d. I will give an overview of the method, derive necessary jump conditions for objects represented by triangular meshes, and then discuss how to parallelize the method. Numerical examples will be shown to test the accuracy, efficiency and robustness of the method. [Preview Abstract] |
Tuesday, November 22, 2016 9:05AM - 9:18AM |
M27.00006: Simulations of Compressible Viscous Flows and Wave Scattering Using the Immersed Boundary Method Walter Arias-Ramirez, Britton J. Olson, William R. Wolf The immersed boundary method (IBM) in combination with a high-order finite difference compact formulation is used to study canonical test cases in fluid mechanics and acoustics, including viscous compressible flows, acoustic wave reflection and diffraction, and shock-wave reflections. In this study, two IB formulations are implemented: the continuous forcing and the discrete forcing approaches. Results obtained for the two methodologies are presented for 1-D problems involving acoustic and shock wave reflection, plane wave acoustic scattering along a cylinder and the viscous flow past a solid cylinder. Additionally, a grid convergence study is carried out for the simulations showing first-order convergence for the current implementation of the continuous forcing approach and second-order convergence for the discrete forcing approach. [Preview Abstract] |
Tuesday, November 22, 2016 9:18AM - 9:31AM |
M27.00007: An immersed boundary method for aeroacoustic flow using a high-order finite difference method Britton Olson An immersed boundary method that achieves second order accuracy in space on acoustic reflection problems is introduced and tested on a number of aero-acoustic related problems. ~The method follows a continuous forcing approach and uses existing solver operators to smoothly extend the flow solution though the immersed boundary. ~Both no-slip and free-slip boundary conditions are demonstrated on complex geometries using a high-order finite difference code on a Cartesian grid. ~High Mach number test problems are also shown, demonstrating the method's robustness in the presence of shock waves. [Preview Abstract] |
Tuesday, November 22, 2016 9:31AM - 9:44AM |
M27.00008: An immersed boundary method for non-uniform Cartesian grids Juwon Jang, Changhoon Lee Many kinds of immersed boundary method have been developed, but most of them have been used in uniform grids with discrete Dirac delta functions. Therefore, the distribution of Lagrangian points over the immersed surface is usually made uniformly. However, when any immersed boundary method is to be applied to non-uniform grids, uniform distribution might not be optimum for good performance. Recently, Akiki and Balachandar (2016) proposed a method to distribute the Lagrangian points nonuniformly over the surface of a sphere near the wall, but it cannot not be extended to more general shape of immersed surface. We propose a method that is capable for properly distributing the Lagrangian points over any kind of surface by considering the size of nearby Eulerian grids. Present method first finds intersection points between immersed surface and nonuniform Cartesian grids. Then, the centroid of the intersection points is projected on the immersed surface to be designated by Lagrangian point. This procedure guarantees one Lagrangian point per the Eulerian grid cell. This method is validated for various problems such as flows around a settling sphere, a moving sphere in the near-wall region and a tilted ellipsoid near the wall. [Preview Abstract] |
Tuesday, November 22, 2016 9:44AM - 9:57AM |
M27.00009: Efficient ghost cell reconstruction for embedded boundary methods Narsimha Rapaka, Mohamad Al-Marouf, Ravi Samtaney A non-iterative linear reconstruction procedure for Cartesian grid embedded boundary methods is introduced. The method exploits the inherent geometrical advantage of the Cartesian grid and employs batch sorting of the ghost cells to eliminate the need for an iterative solution procedure. This reduces the computational cost of the reconstruction procedure significantly, especially for large scale problems in a parallel environment that have significant communication overhead, e.g., patch based adaptive mesh refinement (AMR) methods. In this approach, prior computation and storage of the weightage coefficients for the neighbour cells is not required which is particularly attractive for moving boundary problems and memory intensive stationary boundary problems. The method utilizes a compact and unique interpolation stencil but also provides second order spatial accuracy. It provides a single step/direct reconstruction for the ghost cells that enforces the boundary conditions on the embedded boundary. The method is extendable to higher order interpolations as well. Examples that demonstrate the advantages of the present approach are presented. [Preview Abstract] |
Tuesday, November 22, 2016 9:57AM - 10:10AM |
M27.00010: ABSTRACT WITHDRAWN |
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