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 HD: CFD II: Immersed Boundary Methods and Fluid-Structure Interaction |
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Chair: Jianming Yang, University of Iowa Room: Long Beach Convention Center 102B |
Monday, November 22, 2010 10:30AM - 10:43AM |
HD.00001: ABSTRACT WITHDRAWN |
Monday, November 22, 2010 10:43AM - 10:56AM |
HD.00002: Curvilinear Immersed Boundary Method for Simulating Sediment Transport and Scour in Open Channel Flows Ali Khosronejad, Seokkoo Kang, Iman Borazjani, Fotis Sotiropoulos The fluid-structure interaction curvilinear immersed boundary numerical method of Borazjani et al. (J. Comp. Physics 2008) is extended to simulate coupled flow and sediment transport phenomena. The method is inherently suited for carrying out coupled flow/morphodynamics simulations in natural waterways with arbitrarily complex bed bathymetry and embedded hydraulic structures as it eliminates the need for the mesh to conform to the continuously evolving bed forms. The URANS equation with the k-w turbulence model with wall functions is used for turbulence closure. The Exner equation is discretized using an unstructured finite-volume formulation to determine the dynamic deformation of the bed. The physical phenomenon of sand-slide at places with steep bed slope is accounted for by implementing a mass-balance based algorithm. The flow field and bed morphodynamics equations are coupled using a partitioned loose- coupling approach. The predictive capabilities of the method are demonstrated by simulating the bed deformation in curved open channels with embedded hydraulic structures. [Preview Abstract] |
Monday, November 22, 2010 10:56AM - 11:09AM |
HD.00003: A Simple and Efficient Sharp Interface Immersed Boundary Method for Fluid-Structure Interaction with Complex Rigid Bodies Jianming Yang, Frederick Stern A sharp interface immersed boundary method is presented for the simple and efficient simulation of fluid-structure interaction with complex three-dimensional rigid bodies. The previous formulation by Yang and Balaras (An Embedded-Boundary Formulation for Large-Eddy Simulation of Turbulent Flows Interacting with Moving Boundaries, J. Comput. Phys. 215 (2006) 12-40) is greatly simplified without sacrificing the overall accuracy. In addition, a novel, highly efficient non-iterative coupling scheme is developed for the simulation of a viscous flow interacting with multiple bodies. Several cases are examined to demonstrate the accuracy, simplicity and efficiency of the new method. [Preview Abstract] |
Monday, November 22, 2010 11:09AM - 11:22AM |
HD.00004: Three-dimensional simulation of a valveless pump Soo Jai Shin, Hyung Jin Sung An immersed boundary (IB) method for simulating a three-dimensional valveless pump is described. The valveless pump is treated as an elastic tube connected at its ends to a rigid tube. The governing equation for the motion of the elastic tube is derived by using the variational derivative of the deformation energy. Our method is based on an efficient Navier-Stokes solver that uses the fractional step method and a staggered Cartesian grid system. The fluid motion defined on an Eulerian grid and the structure motion defined on a moving Lagrangian grid are independently solved, and their interaction is formulated by using momentum forcing. A net flow is generated inside the valveless pump through the periodic pinching of the elastic tube at a position that is asymmetric with respect to its ends. Two valveless pumps are chosen, a single valveless pump and a double valveless pump. The effects on the average flow rate of varying the pinching frequency and the pinching position were investigated. The interaction between the wave dynamics and the inertia of the returning flow was examined for a closed loop system. [Preview Abstract] |
Monday, November 22, 2010 11:22AM - 11:35AM |
HD.00005: Simulations of the Motion of Arbitrarily Shaped Fibers in a Linear Shear Flow Andriy Roshchenko, Warren Finlay, Peter Minev Fibrous airborne particles cause severe adverse health effects when inhaled and deposited in human lungs. For this reason, fiber deposition in the lungs has been studied by numerous authors. However, a complete mechanistic model of fiber dynamics in the lungs has not yet been presented. One of the problems yet to be addressed involves the dynamics of arbitrarily shaped fibers in the lungs. Here, a two-grid fictitious domain method was used for direct simulations of arbitrarily shaped high aspect ratio fibers in linear shear flow, including an improved microscale grid resolution scheme and a Lagrangian-Eulerian approach whereby we transform the equations from a laboratory coordinate system to one fixed with the microgrid. Our simulations show the expected Jeffery orbits for straight, symmetric fibers. However, for asymmetric fiber shapes we observe a surprising secondary rotation that is out of the shear plane. Our findings suggest that studies of deposition efficiencies of fibrous aerosols should account for possible increases in deposition due to asymmetrical aerosol particles or their aggregations. [Preview Abstract] |
Monday, November 22, 2010 11:35AM - 11:48AM |
HD.00006: Fluid-Solid Interactive Methodology for Prognosis of Passenger Jet Structural Damage in Water Crash Landing Javid Bayandor Today, crashworthiness studies constitute a major part of modern aerospace design and certification processes. Of important consideration is the assessment of structural damage tolerance in terms of the extent of progressive damage and failure caused by aircraft emergency ditching on soft terrain or on water. Although a certification requirement, full scale crash landings are rarely tested using fully functional prototypes due to their high associated costs. This constraint makes it difficult for all crashworthy features of the design to be identified and fine-tuned before the commencement of the manufacturing phase. The current study presents aspects of a numerical methodology that can drastically subside the dependency of the certification assessments to full scale field trials. Interactive, fully nonlinear, solid-structure and fluid- structure analyses have been proposed using coupled Lagrangian- Eulerian and independent meshless Lagrangian approaches that run on a combined finite element-computational fluid dynamics platform. Detailed analysis of a key landing scenario pertaining to a large passenger jet will be provided to determine the relevance and accuracy of the proposed method. The work further identifies state-of-the-art computational approaches for modeling fluid-solid interactive systems that can help improve aircraft structural responses to soft impact and water ditching. [Preview Abstract] |
Monday, November 22, 2010 11:48AM - 12:01PM |
HD.00007: A discrete-forcing immersed boundary method for the fluid-structure interaction of an elastic slender body Injae Lee, Haecheon Choi In the present study, an immersed boundary method for the simulation of flow around an elastic slender body is developed. The present method is based on the discrete forcing method by Kim et al. (J. Comput. Phys., 2001) and is fully coupled with the elastic slender body motion. The incompressible Navier- Stokes equations are solved in an Eulerian coordinate and the elastic slender body motion is described in a Lagrangian coordinate, respectively. The elastic slender body is assumed as a thin flexible beam and is segmented by finite blocks. Each block is then moved by the external and internal forces such as the hydrodynamic, tension, bending, and buoyancy forces. We simulate several flow problems and the results agree very well with those from previous studies. Moreover, the present method does not impose any severe limitation on the size of computational time step due to the numerical stability. [Preview Abstract] |
Monday, November 22, 2010 12:01PM - 12:14PM |
HD.00008: Effects of mass ratio to flexible flapping-wing propulsion Min Xu, Mingjun Wei, Tao Yang, Thomas Burton In our previous work, we used a strong-coupling approach to simulate highly flexible wings interacting with surrounding fluid flows. However, there was a strong assumption: the wing structure has the same density as the surrounding fluid. Though this assumption has greatly simplified the formulation and worked well in most of our previous studies, it made impossible to consider the effects of mass ratio between the structure and fluid. In this study, we introduced another body force term to represent the density difference and also modified the formulation so that almost no extra cost was added in order to consider the mass ratio effects. Using the new algorithm, we found an interesting nonlinear response of the trailing-edge frequency to the active plunging frequency at the leading edge when certain flapping frequency and mass ratio were chosen. [Preview Abstract] |
Monday, November 22, 2010 12:14PM - 12:27PM |
HD.00009: A fully-coupled approach to simulate three-dimensional flexible flapping wings Tao Yang, Mingjun Wei The algorithm in this study is based on a combined Eulerian description of both fluid flow and solid structure which then can be solved in a monolithic manner. Thus, the algorithm is especially suitable to solve fluid-structure interaction problems involving large and nonlinear deformation. In fact, we have successfully applied the same approach to our previous study of two-dimensional pitching-and-plunging problems and found many unique features from the passive pitching introduced by wing flexibility. With the current non-trivial extension of the algorithm to three-dimensional configuration, we can eventually reveal the complex vortex and structural dynamics behind the amazing performance of nature's fliers such as hummingbirds. [Preview Abstract] |
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