Bulletin of the American Physical Society
60th Annual Meeting of the Divison of Fluid Dynamics
Volume 52, Number 12
Sunday–Tuesday, November 18–20, 2007; Salt Lake City, Utah
Session FD: Biofluids V |
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Chair: Fotis Sotiropoulos, University of Minnesota Room: Salt Palace Convention Center 151 A-C |
Monday, November 19, 2007 8:00AM - 8:13AM |
FD.00001: Pulse propagation in the pulmonary arteries Nicholas Hill, Gareth Vaughan, Mette Olufsen, Martin Johnson, Christopher Sainsbury The model of Olufsen [1,2] has been extended to study pulse propagation in the pulmonary circulation. The pulmonary arteries are treated as a bifurcating tree of compliant and tapering vessels. The model is divided into two coupled parts: the larger and smaller arteries. Blood flow and pressure in the larger arteries are predicted from a nonlinear 1D cross-sectional area-averaged model for a Newtonian fluid in an elastic tube. The initial cardiac output is obtained from magnetic resonance measurements. The smaller blood vessels are modelled as an asymmetric structured tree with specified area and asymmetry ratios between the parent and daughter arteries. Womersley's theory gives the wave equation in the frequency domain for the 1D flow in these smaller vessels, resulting in a linear system. The impedances of the smallest vessels are set to a constant and then back-calculation gives the required outflow boundary condition for the Navier-Stokes equations in the larger vessels. The number of generations of blood vessels, and the compliance of the arterial wall are shown to affect both the systolic and diastolic pressures. [1] Olufsen MS et al. Ann Biomed Eng. 2000;28:1281-99. [2] Olufsen MS. Am J Physiol. 1999;276:H257-68. [Preview Abstract] |
Monday, November 19, 2007 8:13AM - 8:26AM |
FD.00002: Pumping Dynamics in The Embryonic Heart Tube Morteza Gharib, Arian Forouhar, Scott Fraser The embryonic vertebrate heart is a compliant dynamic tube that develops into a multi-chambered multi-valve geometry at later stages. Even at these early stages, the tubular embryonic heart pumps blood to sustain the circulatory system. The prevailing understanding of the pumping mechanism at these stages describes the heart tube as a peristaltic pump. Through advanced confocal imaging techniques, we examined the movement of cells in the embryonic heart tube and the flow of blood through the heart and obtained results that contradict peristalsis as a pumping mechanism in the embryonic heart. We propose a more likely explanation of early cardiac dynamics in which the pumping action results from suction due to elastic wave propagation in the heart tube. [Preview Abstract] |
Monday, November 19, 2007 8:26AM - 8:39AM |
FD.00003: Three-dimensional quantitative analysis of cardiovascular flow and heart wall motions in living zebrafish embryos Jian Lu, Scott Fraser, Morteza Gharib Progenitor factors such as blood flow induced mechanical forces play a key role in vertebrate heart development. However, three-dimensional (3-D) characteristics of in vivo cardiovascular flow and heart wall motions are not well understood due to the lack of proper imaging tools with sufficient spatial and temporal resolutions for quantitative analysis. In this study, a real-time high-speed 3-D imaging system based on defocusing digital particle image velocimetry was used to study dynamic cell motions in living zebrafish embryos. 500-nm fluorescent microspheres were injected into the blood stream to label the cardiovascular flow. Cardiac blood flow velocities were measured during a cardiac cycle at various early embryonic stages. The heart wall of a zebrafish embryo was labeled by a few fluorescent microspheres adhered to the wall. 3-D dynamic motions were reconstructed and quantitative analysis such as strain measurement was performed. [Preview Abstract] |
Monday, November 19, 2007 8:39AM - 8:52AM |
FD.00004: Fluid structure interaction (FSI) simulation of bileaflet mechanical heart valve in an anatomic aorta geometry Liang Ge, Iman Borazjani, Lakshmi Dasi, Fotis Sotiropoulos, Ajit Yoganathan FSI simulation of a medical quality BMHV implanted in the aortic position is studied. The valve is implanted in an anatomic non-compliant aorta geometry, which is reconstructed from MRI data acquired from a healthy volunteer. A physiological incoming flow waveform is specified at the inlet with the peak systolic Reynolds number equal to 6000. The flow solver is based on the CURVIB (curvilinear immersed boundary method) of Ge and Sotiropoulos, 2007 (JCP) and the FSI problem is solved with strong coupling partitioned approach. Direct numerical simulation is carried out on a grid system consisting of 10M grid nodes. The impact on hemodynamics by valve implantation is studied by considering different valve implantation angles. The calculated numerical results are analyzed in terms of leaflet kinematics and flow physics, and compared with data from our previous work, where the same valve is implanted in a simplified straight aorta geometry. [Preview Abstract] |
Monday, November 19, 2007 8:52AM - 9:05AM |
FD.00005: Dynamic simulation of chorded mitral valve in a left ventricle using an immersed boundary method Xiaoyu Luo, Min Yin, Chunlei Liang, Tiejun Wang, Paul Watton We use an immersed boundary model to investigate the dynamic behaviour of a chorded mitral prosthesis placed within a left ventricle under physiological flow conditions. \textit{In vivo} magnetic resonance images of the left ventricle are used to create a numerical ventricle model. The motion of the ventricle model is prescribed during a cardiac cycle. Fluid-structure interaction simulations are carried out to test the performance of the mitral valve in a more realistic physiological environment. These simulations enable us to assess the effect of the ventricle motion, especially its flow vortex structure, on the function of the chorded mitral valve. [Preview Abstract] |
Monday, November 19, 2007 9:05AM - 9:18AM |
FD.00006: Flow Dynamics in a Coupled Circulatory-Respiratory System Carolyn Kaplan, Anne Staples, Elaine Oran, K. Kailasanath, Jay Boris We describe simulations of flow in a network of fluid channels that represent a coupled circulatory and respiratory system. Each channel is one-dimensional and can have a variable cross sectional area. The circulatory flow is driven by a sinusoidal pressure pulse triggered by a chemical signal based on the oxygen content in the blood. Space and time scales are calibrated to the properties of an average person. We discuss the effects of branching (increasing the numbers of interconnected channels) and varying the strength and frequency of perturbations from the mean. [Preview Abstract] |
Monday, November 19, 2007 9:18AM - 9:31AM |
FD.00007: ABSTRACT WITHDRAWN |
Monday, November 19, 2007 9:31AM - 9:44AM |
FD.00008: Flow Structure Downstream of a Mechanical Heart Valve during Systole: Investigation Using High-Speed Particle Image Velocimetry Peter Oshkai, Farida Haji-Esmaeili High speed digital particle image velocimetry is employed to study turbulent flow through a bileaflet mechanical heart valve during systolic and diastolic phases of a cardiac cycle. Unsteady vortex shedding from the valve's leaflets displays distinct characteristic frequencies, depending on the opening angle of each leaflet. Small- and large-scale transverse oscillations of the separated shear layers are studied using global quantitative flow imaging approach. Implementation of high-speed digital particle image velocimetry technique yields quantitative information about vortex shedding frequencies and trajectories of the shed vortices downstream of the valve. Turbulent flow structures including jet-like regions and shed vortices are characterized in terms of patterns of instantaneous and time-averaged velocity, vorticity, and streamline topology. [Preview Abstract] |
Monday, November 19, 2007 9:44AM - 9:57AM |
FD.00009: Optimization and surgical design for applications in pediatric cardiology Alison Marsden, Adam Bernstein, Charles Taylor, Jeffrey Feinstein The coupling of shape optimization to cardiovascular blood flow simulations has potential to improve the design of current surgeries and to eventually allow for optimization of surgical designs for individual patients. This is particularly true in pediatric cardiology, where geometries vary dramatically between patients, and unusual geometries can lead to unfavorable hemodynamic conditions. Interfacing shape optimization to three-dimensional, time-dependent fluid mechanics problems is particularly challenging because of the large computational cost and the difficulty in computing objective function gradients. In this work a derivative-free optimization algorithm is coupled to a three-dimensional Navier-Stokes solver that has been tailored for cardiovascular applications. The optimization code employs mesh adaptive direct search in conjunction with a Kriging surrogate. This framework is successfully demonstrated on several geometries representative of cardiovascular surgical applications. We will discuss issues of cost function choice for surgical applications, including energy loss and wall shear stress distribution. In particular, we will discuss the creation of new designs for the Fontan procedure, a surgery done in pediatric cardiology to treat single ventricle heart defects. [Preview Abstract] |
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