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 D31: CFD: Immersed Boundary Methods |
Hide Abstracts |
Chair: Aleksander Donev, New York University Room: 2018 |
Sunday, November 23, 2014 2:15PM - 2:28PM |
D31.00001: Imposing scalar fluxes with the immersed boundary method in WRF Jingyi Bao, Katherine Lundquist, Fotini Chow The Weather Research and Forecasting model (WRF) is being used over increasingly complex terrain at higher grid resolutions. However, when it comes to the situation of complex terrain, resolved terrain slopes can become large, causing numerical errors from grid stretching of the terrain-following coordinates. An immersed boundary method (IBM), a non-conforming grid technique was recently implemented into WRF (Lundquist et al. 2010, 2012), to alleviate numerical errors associated with the extreme distortion of the grid cells. The IBM uses a Cartesian grid with the terrain boundary ``immersed'' within the grid. The force of the boundaries on the fluid is represented with the addition of a body force term in the momentum equation. In this work, we extend the existing WRF-IBM model to represent the Neumann boundary condition at the surface for potential temperature and moisture in order to simulate realistic atmospheric flows. The Neumann boundary condition for potential temperature and moisture is designed to accommodate different closures, such as the most common Smagorinsky closure. Validation test cases include thermally induced slope flows in an idealized valley with both coupled and uncoupled heat fluxes. In the uncoupled cases, the surface heating is specified as a function of time, and there are no surface or land attributes such as vegetation or soil type. In the coupled cases, the surface fluxes are prescribed by atmospheric parameterizations, which have been modified to recognize the immersed boundary as the terrain surface. These test cases will provide a proof of concept and verify the implementation of the new temperature and moisture boundary conditions. [Preview Abstract] |
Sunday, November 23, 2014 2:28PM - 2:41PM |
D31.00002: Immersed boundary methods for particles in viscoelastic drilling muds Sreenath Krishnan, Eric Shaqfeh, Gianluca Iaccarino In fracture stimulation of oil and gas wells, polymeric solution with suspended solids (proppants) are pumped to prop open the fracture. The primary aim of our work is to understand the dynamics of such proppants under various flow conditions through numerical computations. The study is concerned with fully resolved simulations, wherein all scales associated with the particle motion and the flow are resolved. The present effort is based on the algorithm proposed by Patankar (CTR Annual Research Briefs 2001:185-196), i.e. the Immersed Boundary (IB) methods, in which the domain grids do not conform to particle geometry and for simplicity are chosen to be Cartesian. Since Cartesian grids cannot efficiently represent a fracture geometry, our focus is on the development of an IB method for viscoelastic flows in unstructured domain grids. This method is implemented in a massively parallel, unstructured finite-volume-based fluid solver developed at Stanford University. The main theme of the presentation will be the description of the algorithm, measures taken to enable efficient parallelization and transfer of information between the underlying fluid grid and the particle mesh. A number of flow simulations will be presented, which validates the accuracy and correctness of the algorithm. [Preview Abstract] |
Sunday, November 23, 2014 2:41PM - 2:54PM |
D31.00003: Characteristic-based Volume Penalization Method for Arbitrary Mach Flows Around Solid Obstacles Nurlybek Kasimov, Eric Brown-Dymkoski, Oleg Vasilyev A new volume penalization method to enforce immersed boundary conditions in Navier-Stokes and Euler equations is presented. Previously, Brinkman penalization has been used to introduce solid obstacles modeled as porous media. This approach is limited to Dirichlet-type conditions on velocity and temperature, and in inviscid supersonic flows led to wrong shock reflection. It builds upon Brinkman penalization by allowing Neumann and Robin conditions to be applied in a general fashion. Correct boundary conditions are achieved through characteristic propagation into the thin layer inside of the obstacle. Inward pointing characteristics ensure that nonphysical solution inside the obstacle does not propagate out to the fluid region. Dirichlet boundary conditions are enforced similarly to Brinkman method. Penalization parameters are chosen so they act on a much faster timescale than the characteristic timescale of the flow. Main advantage of this method is the systematic means of controlling the error. This approach is general and applicable to a wide variety of flow regimes. The extensions of the methodology to moving obstacles and three dimensional flows are discussed. [Preview Abstract] |
Sunday, November 23, 2014 2:54PM - 3:07PM |
D31.00004: Effect of gravity on the finite-size particle within spectral resolution Yongnam Park, Changhoon Lee This study aims at the finest simulation of~settling~particles by using the immersed boundary method and direct numerical simulation with pseudo-spectral scheme. In many particle-laden simulations with the point-particle approach, due to the heavy particle approximation only Stokes drag force and gravity force are taken into account. On the other hand, most published works using an immersed boundary method considered particles as large as the Talyor micro scale. However, the Stokes number of particle of the Taylor micro scale size is over hundreds such that particles are not directly affected by turbulent flows. Due to the large Stokes number of finite-size particles, the density ratio of finite-size particles is limited to small range. In this study, the size of particles is comparable with the Kolmogorov length scale, and density ratio is larger than 10 in order to compare the results by the point particle simulations. In this simulation range, settling particles attenuate the turbulence because the particles can easily penetrate the vortex core and disturb the evolution of turbulence. Detailed statistics of particle motion will be discussed in the presentation. [Preview Abstract] |
Sunday, November 23, 2014 3:07PM - 3:20PM |
D31.00005: ABSTRACT WITHDRAWN |
Sunday, November 23, 2014 3:20PM - 3:33PM |
D31.00006: Implementation of Immersed Boundary Method in WENO Scheme to Simulate Blast-Structure Interaction Min Xu, Tao Yang, Mingjun Wei High-order WENO schemes have been widely used in numerical simulation of shock/blast waves; and immersed boundary method has been gradually accepted as a simple and powerful approach to deal with moving boundaries in computational fluid dynamics. The combination of these two techniques becomes a natural choice in our study of blast-structure interaction. To benchmark our combined approach, we applied it first on classical shockwave problems with exact solutions or well-tested numerical solutions. Then, the algorithm is applied to simulate the interaction between an incoming blast wave and a spring-linked cylinder. Finally, a more complex case, where multiple plates linked by springs are interacting with blast waves and each other, has been investigated. [Preview Abstract] |
Sunday, November 23, 2014 3:33PM - 3:46PM |
D31.00007: Improvements to Level Set, Immersed Boundary methods for Interface Tracking Chris Vogl, Randy LeVeque It is not uncommon to find oneself solving a moving boundary problem under flow in the context of some application. Of particular interest is when the moving boundary exerts a curvature-dependent force on the liquid. Such a force arises when observing a boundary that is resistant to bending or has surface tension. Numerically speaking, stable numerical computation of the curvature can be difficult as it is often described in terms of high-order derivatives of either marker particle positions or of a level set function. To address this issue, the level set method is modified to track not only the position of the boundary, but the curvature as well. The definition of the signed-distance function that is used to modify the level set method is also used to develop an interpolation-free, closest-point method. These improvements are used to simulate a bending-resistant, inextensible boundary under shear flow to highlight area and volume conservation, as well as stable curvature calculation. [Preview Abstract] |
Sunday, November 23, 2014 3:46PM - 3:59PM |
D31.00008: A Fluctuating Immersed Boundary Method for Brownian Suspensions of Rigid Particles Aleksandar Donev I will describe how to model Brownian suspensions of passive or active particles and rigid bodies using an immersed boundary (IB) approach. I will first discuss minimally-resolved models in which each suspended spherical particle is represented by a single IB marker [F. Balboa Usabiaga and R. Delgado-Buscalioni and B. E. Griffith and A. Donev, Computer Methods in Applied Mechanics and Engineering, 269:139-172, 2014; and S. Delong, F. Balboa Usabiaga, R. Delgado-Buscalioni, B. E. Griffith and A. Donev, J. Chem. Phys., 140, 134110, 2014]. More complex rigid bodies suspensed in fluid can be represented with different degrees of fidelity by enforcing a rigidity constraint for each partially- or fully-resolved body [B. Kallemov, A. Bhalla, A. Donev, and B. Griffith, in preparation]. Thermal fluctuations and thus Brownian motion can be consistently modeled by including a fluctuating (random) stress in the momentum equation, as dictated by fluctuating hydrodynamics. [Preview Abstract] |
Sunday, November 23, 2014 3:59PM - 4:12PM |
D31.00009: The Immersed Interface Method with Triangular Mesh Representation of an Interface Sheng Xu The immersed interface method can be employed to solve an interface problem on a fixed Cartesian grid by incorporating necessary interface-induced Cartesian jump conditions into numerical schemes. In this talk, we present ideas to compute the necessary Cartesian jump conditions from given principal jump conditions using triangular mesh representation of an interface. The triangular mesh representation is simpler and more robust than interface parametrization for a complex or non-smooth interface. We test our ideas by using the computed Cartesian jump conditions in the immersed interface method to solve a Poisson equation subject to an interface with the shape of a sphere, cube, cylinder or cone. Our results demonstrate expected second-order accuracy in the infinity norm. [Preview Abstract] |
Sunday, November 23, 2014 4:12PM - 4:25PM |
D31.00010: Adaptive wavelet-based framework for aeroelastic simulations Raj Nair, Oleg Vasilyev This study presents the novel adaptive wavelet-based framework for modeling fluid-structure interaction. The approach uses the adaptive wavelet collocation method to solve the linear-elastic structural deformation equations inside the solid obstacle and compressible Navier-Stokes equations in the outer fluid region. The method then combines two mathematical approaches: volume penalization for creating a fluid-structure coupling by specifying traction condition on the solid boundary and enforcing the no-slip velocity conditions consistent with the rate of structural deformation on the obstacle boundary and a level-set-method, which dynamically tracks the solid-fluid interface. The method is applied to a two-dimensional aeroelastic flow and preliminary results are discussed. This work serves as the basis for continuing development of a robust adaptive wavelet based fluid-structure interaction model to accurately model the effects of unsteady aerodynamic loads in aeroelastic 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