Bulletin of the American Physical Society
2005 58th Annual Meeting of the Division of Fluid Dynamics
Sunday–Tuesday, November 20–22, 2005; Chicago, IL
Session EA: Bio-Fluid Dynamics: Pumps, Pumping, and Transport |
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Chair: Kenneth Christensen, University of Illinois, Urbana-Champaign Room: Hilton Chicago International Ballroom South |
Sunday, November 20, 2005 4:10PM - 4:23PM |
EA.00001: Wave Model for Valveless Pumping based on Impedance and Resonance Anna Hickerson, Morteza Gharib Valveless pumping can be achieved through the periodic compression of a pliant tube asymmetrically from its interfaces to different tubing or reservoirs. Flow and pressure measurements revealed resonant properties of the pump mechanics that suggest a mechanism of how the pump functions based on wave propagation and reflections. For each compression, a pair of pressure waves is created. These waves will travel, reflect, dissipate, distort and interact. The sum of these behaviors is responsible for the net pressures and flows observed. A simple mathematical model of wave interactions in conjunction with the geometric properties of the experiments showed remarkable agreement with the experimental results. [Preview Abstract] |
Sunday, November 20, 2005 4:23PM - 4:36PM |
EA.00002: Experimental Assessment of Flow Within a Pediatric Ventricular Assist Device K.T. Christensen, E. Ferrara, M. Muramatsu, I.A. Cestari Particle-image velocimetry is used to study the flow within a pediatric ventricular assist device (PVAD) operating in the range of 60--100~beats per minute, with particular interest in identifying flow patterns that may promote detrimental processes like hemolysis and/or thrombosis. To this end, phase-locked PIV measurements are made in planes parallel to a pneumatically-driven membrane that controls the flow into and out of the PVAD's blood chamber. Preliminary results show that velocities exceeding 1~m/s can exist in these relatively small devices and that the instantaneous flow patterns can be quite vigorous. In particular, while phase-averaged fields appear to represent the bulk, large-scale features of the flow within the blood chamber of the PVAD, small-scale cycle-to-cycle variability is also quite apparent, most notably during the diastole phase when the membrane is retracting from the blood chamber. This cycle-to-cycle variability is found to increase with beating frequency. [Preview Abstract] |
Sunday, November 20, 2005 4:36PM - 4:49PM |
EA.00003: WITHDRAWN: Valveless Pumping: Theory and Experimental Validation Thomas Bringley, Stephen Childress, Nicholas Vandenberghe, Jun Zhang An elastic tube connected in a ring to a rigid tube, filled with water, and squeezed periodically off-center produces a net flow around the tubes. This phenomenon, known as valveless pumping, is thought to have applications to the biology of blood circulation as well as to the design of practical pumps, particularly at the micro-scale. At the 2004 DFD meeting, we described an experimental study and a simple model of such a system. The experimental system successfully pumped fluid, and we also observed flow reversals and resonances. Since, we have made improvements to our (still simple) model, and its results now better match those of the experiment. We have also made significant advances in our mathematical understanding of the model, including deriving an asymptotic expression for the average flux in the pump that reveals the effects of changing any of the physical parameters. We find several surprising results about the roles of wave propagation, nonlinear advection, and the stiffness of the elastic tube in valveless pumping. Also, we are able to explain the flow reversals observed in the experiment. Our conclusions from the model are confirmed by experimental results. [Preview Abstract] |
Sunday, November 20, 2005 4:49PM - 5:02PM |
EA.00004: How Does the Stomach Pump?---A Fluid Dynamics Discovery Anupam Pal, James Brasseur, Bertil Abrahamsson The stomach is a pump that empties viscous liquid from a flexible bag (fundus) through a valve (pylorus) by slow squeeze of fundic muscle. In addition, peristaltic contraction waves (CW) travel periodically towards the pylorus in the lower stomach to grind/mix content. As each CW approaches the pylorus, it deepens and the pylorus momentarily closes. Since liquid empties from the pyloric region, one expects content at the farthest reaches of the stomach to empty last. To study the patterns of gastric emptying we applied the lattice Boltzmann method with moving boundary conditions coupled with a stomach geometry model parameterized using MRI. By marking fluid particles leaving the stomach over a 10 min period, we discovered that the CWs create a \textit{narrow} \textit{path of emptying}, or ``Magenstrasse'' (stomach road) that directs content from the farthest reaches of the stomach to the pylorus with relatively little mixing. Thus, while drug released off the Magenstrasse (MS) can take an hour or more to empty at low concentration, when released on the MS the drug empties within 10 minutes at high concentration---a discovery with potential implications to other pumping systems. [Preview Abstract] |
Sunday, November 20, 2005 5:02PM - 5:15PM |
EA.00005: Analysis of Peristaltic Mixing and Transport Processes in the GI Tract Sreedevi Krishnan, Seth Dillard, H.S. Udaykumar Nutrient absorption, mixing and breakdown takes place in the GI tract in the laminar flow regime by the action of peristaltic contraction waves. Several engineering applications demand effective methods for mixing of fluids of varying consistency. Adopting the physiological system as a model for the design of optimal mechanical systems requires full understanding of the physics involved. An Eulerian Levelset based sharp interface method with Lagrangian particle tracking is used to perform detailed computational analysis of the flow, transport and mixing in a model intestine under the action of peristaltic waves. Mixing is quantified by mixing measures, mixing maps, stretch rates and rotation rates. Results show complex dynamics of mixing by action of moving walls, vortex formation and shedding. Insights are obtained into the fluid mechanics in the gastrointestinal tract over a wide parameter space influencing mixing and transport, including particle size, mass, initial placement of the bolus, frequency and amplitude of the peristaltic wave and wave train effects. [Preview Abstract] |
Sunday, November 20, 2005 5:15PM - 5:28PM |
EA.00006: Performance of mosquito's pump Kenji Kikuchi, Nobuyuki Terada, Osamu Mochizuki The flow of human blood in Mosquito's proboscis on Hagen-Poiseuille flow is investigated by using micro PIV system to apply mosquito's sucking system for micro-TAS devises. We want to know how high the power of Mosquito's pump is and how small the resistance in a proboscis is, a structure of Mosquito's sucking pump, and its characteristics as mechanical pump. We made the mosquito suck blood of our arm to obtain the average value, made many slices of a mosquito with 2$\mu $m thickness after fixed by wax. We anatomized the mosquito's head and picked up the sucking pump under the microscope to know its volume. Mosquito's pump shows high performance compared with the artificial pumps. The surfaces of proboscis were taken by using SEM, AFM because it is important factor for interaction between flow and its wall. Visualization of the blood flows near the tip of and inside proboscis are taken by micro PIV system to know the flow rate. We estimate the power of pump and the friction drag of proboscis by using these data. [Preview Abstract] |
Sunday, November 20, 2005 5:28PM - 5:41PM |
EA.00007: WITHDRAWN: Modeling of Transient Phenomena in an Axial Flow Blood Pump Houston Wood, Alexandrina Untaroiu A fully implantable axial flow Ventricular Assist Device (VAD) has been developed with a magnetically suspended impeller (LEV-VAD). The LEV-VAD's flow path design provides a single pass blood path with minimal turbulence. The pump design included the extensive use of CFD modeling and experimental validation under steady-state flow conditions. This CFD study explores transient flow phenomena in the pump simulating in vivo flow conditions. The LEV-VAD operates under transient conditions due to the pulsatile inlet flow rate induced by the patient's native heart and the spinning of the impeller. This study considered: (1) Time varying boundary conditions (TVBC); (2) Stationary-rotating blades interaction or transient sliding interfaces (TSI). The LEV-VAD performance and pressure-flow correlations were investigated under transient flow conditions. The fluid forces acting on the impeller were calculated to facilitate the suspension system and motor design. The transient simulations illustrate the LEV-VAD's response to dynamic flow conditions and demonstrated the ability to deliver flows from 2 to 10 LPM at rotational speeds varying from 5,000 to 8,000 RPM for physiological pressures corresponding to adult CHF patients. [Preview Abstract] |
Sunday, November 20, 2005 5:41PM - 5:54PM |
EA.00008: Flow Structure Associated with Hemodialysis Catheters Jason Foust, Donald Rockwell Insertion of a hemodialysis catheter into the superior vena cava (SVC) gives rise to complex flow patterns, which arise from the simultaneous injection and extraction of blood through different holes (ports) of the catheter. Techniques of high-image-density particle image velocimetry are employed in a scaled-up water facility. This approach allows characterization of both the instantaneous and time-averaged flow structure due to generic classes of side hole geometries. The trajectory of the injection jet is related to the ratio of the initial jet velocity to the mainstream velocity through the SVC, and to the type of distortion of the jet cross-section. Furthermore, the mean and fluctuating velocity and vorticity fields are determined. Significant turbulent stresses develop rapidly in the injection jet, which can impinge upon the wall of the simulated SVC. Immediately downstream of the injection hole, a recirculation cell of low velocity exists adjacent to the catheter surface. These and other representations of the flow structure are first evaluated for a steady throughflow, then for the case of a pulsatile waveform in the SVC, which matches that of a normal adult. [Preview Abstract] |
Sunday, November 20, 2005 5:54PM - 6:07PM |
EA.00009: Visualization of Transport Phenomena in Regenerated Cartilage Tissue Kenta Haari, Masao Watanabe, Yoshinori Sawae, Toshiyuki Sanada We studied the macroscopic transport phenomena in regenerated articular cartilage tissue. Regenerated cartilage tissue is proposed for the substitution of artificial cartilage as a new medical treatment, to the patient of articular disease such as osteoarthritis. When regenerated cartilage tissue is selected as the therapeutic approach, it should possess not only structural strength as supporting material, but also physiological and biological functions, such as transport of necessary materials to sustain cell activity. Cartilage tissue is significantly different from other tissues for its rich highly sulfated extra cellular matrix (ECM), and is peculiar in its avascularity, hence materials, such as nutrition and oxygen are transported from connected tissue or eriosteum mainly by diffusion. Therefore we focused on this mass diffusion process in cartilage tissue. We engineered regenerated cartilage tissue by seeding chondrocyte into the scaffold of agarose. Diffusion process was visualized by fluorescent tracers saturated in regenerated cartilage tissue. Diffusion measurements were performed during fluorescent tracer desorption from regenerated cartilage tissue to PBS (pH7.4). [Preview Abstract] |
Sunday, November 20, 2005 6:07PM - 6:20PM |
EA.00010: Model for inter-epithelial flow of an anti-HIV microbicidal drug delivery formulation Andrew Szeri, Aaron Weiss, David Katz We consider the spreading characteristics of a Newtonian and a non-Newtonian fluid between compliant surfaces. This is a model for inter-epithelial flow of an anti-HIV microbicidal drug delivery formulation. Squeezing and gravity drive the flow. Owing to the large shear viscosity and narrow flow domain with compliant walls, the problem is an application of elastohydrodynamic lubrication theory. Dimensional analysis and numerical simulation reveal the influence of shear viscosity, wall compliance, longitudinal pressure gradient, formulation volume and channel dimensions on the area coated by the formulation. This area is a function of: (i) a dimensionless parameter which measures the relative importance of gravity-driven and compliance-driven flows, and (ii) time made dimensionless by the compliance and the shear viscosity. The coated area is of central importance in the functioning and evaluation of candidate microbicide delivery systems. [Preview Abstract] |
Sunday, November 20, 2005 6:20PM - 6:33PM |
EA.00011: Hollow-Fiber Cartridges: Model Systems for Virus Removal from Blood Frank Jacobitz, Jeevan Menon, Paul Duffin, Richard Tullis Aethlon Medical is developing a hollow-fiber hemodialysis device designed to remove viruses and toxins from blood. Possible target viruses include HIV and pox-viruses. The filter could reduce virus and viral toxin concentration in the patient’s blood, delaying illness so the patient’s immune system can fight off the virus. In order to optimize the design of such a filter, the fluid mechanics of the device is both modeled analytically and investigated experimentally. The flow configuration of the proposed device is that of Starling flow. Polysulfone hollow-fiber dialysis cartridges were used. The cartridges are charged with water as a model fluid for blood and fluorescent latex beads are used in the experiments as a model for viruses. In the experiments, properties of the flow through the cartridge are determined through pressure and volume flow rate measurements of water. The removal of latex beads, which are captured in the porous walls of the fibers, was measured spectrophotometrically. Experimentally derived coefficients derived from these experiments are used in the analytical model of the flow and removal predictions from the model are compared to those obtained from the experiments. [Preview Abstract] |
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