Bulletin of the American Physical Society
66th Annual Meeting of the APS Division of Fluid Dynamics
Volume 58, Number 18
Sunday–Tuesday, November 24–26, 2013; Pittsburgh, Pennsylvania
Session E9: Biofluids: General III - Pumping Phenomena |
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Chair: Anne Staples, Virginia Polytechnic Institute and State University Room: 333 |
Sunday, November 24, 2013 4:45PM - 4:58PM |
E9.00001: A bioinspired pumping model for flow in a microtube with rhythmic wall contractions Yasser Aboelkassem, Anne Staples Inspired by respiratory systems in insects, in particular the rhythmic wall contractions found in insect tracheal tubes, we propose a bioinspired pumping model that can work particularly well in the low Reynolds number flow regime. Incompressible, viscous flow transport in a fluid-filled axisymmetric, inelastic tube with rhythmic wall contractions is modeled using lubrication theory. The wall motions are prescribed via a tube profile with two contraction sites that can move with a time lag with respect to each other. The analytical model is validated using the method of fundamental solutions based on the Stokeslets meshfree computational method. The velocity field, pressure, and time averaged net flow rate induced in a complete contraction cycle are calculated. The results demonstrate that an inelastic tube with at least two contraction regions (collapse sites) can produce unidirectional flow and working as pumping mechanism. We believe that the physical mechanism underlying the pumping observed in this model relies on the cyclical, temporally asymmetric resistance to upstream and downstream flow that the localized contraction sites exert on one another. [Preview Abstract] |
Sunday, November 24, 2013 4:58PM - 5:11PM |
E9.00002: Electro-dynamic suction pumping at small scales Austin Baird, Laura Miller Dynamic suction pumping is characterized by a bidirectional elastic wave and a non-linear frequency flow relationship. This pumping mechanism has been proposed as the driving mechanism for the vertebrate embryonic heart at the tubular stage. In this study, we consider the tubular, valveless heart of a chordate, the Ascidian \textit{Clavelina picta}. These hearts operate at a Womersley number of about 0.3. We investigate traditional dynamic suction pumping on these small scales and show computationally and experimentally that significant flow isn't achieved. We propose a different pumping mechanism that couples traveling waves of depolarization to the contraction of the boundary. Active contractile waves replace passive elastic waves, but the resulting kinematics are similar to dynamic suction pumping. This pumping mechanism can be computationally shown to drive fluid flow at the low Womersley numbers found in Ascidian hearts. [Preview Abstract] |
Sunday, November 24, 2013 5:11PM - 5:24PM |
E9.00003: Urinal Dynamics Randy Hurd, Kip Hacking, Benjamin Haymore, Tadd Truscott In response to harsh and repeated criticisms from our mothers and several failed relationships with women, we present the splash dynamics of a simulated human male urine stream impacting rigid and free surfaces. Our study aims to reduce undesired splashing that may result from lavatory usage. Experiments are performed at a pressure and flow rate that would be expected from healthy male subjects.\footnote{Lapides, J., Fundamentals of Urology, W.B. Saunders, Philadelphia, 1976.} For a rigid surface, the effects of stream breakup and surface impact angle on lateral and vertical droplet ejection distances are measured using high-speed photography and image processing. For free surface impact, the effects of velocity and fluid depth on droplet ejection distances are measured. Guided by our results, techniques for splash reduction are proposed. [Preview Abstract] |
Sunday, November 24, 2013 5:24PM - 5:37PM |
E9.00004: The Hydrodynamics of Urination: to drip or jet Jonathan Pham, Patricia Yang, Jerome Choo, David Hu The release of waste products is fundamental to all life. How are fluids released from the body quickly and efficiently? In a combined experimental and theoretical investigation, we elucidate the hydrodynamics of urination across five orders of magnitude in animal mass. Using high-speed videography and flow-rate measurement at the Atlanta Zoo, we report discrete regimes for urination style. We observe dripping by small mammals such as rats and jetting by large mammals such as elephants. We discover urination duration is independent of animal size among animals that use jetting. We rationalize urination styles, along with the constant-time scaling, by consideration of the relative magnitudes of the driving forces, gravity and bladder pressure, and the corresponding viscous losses within the urethra. This study may give insight into why certain animals are more prone to diseases of the urinary tract, and how the urinary system evolved under the laws of fluid mechanics. [Preview Abstract] |
Sunday, November 24, 2013 5:37PM - 5:50PM |
E9.00005: The role of amniotic fluid in force transfer during human birth Alexa Baumer, Andrea Lehn, Megan Leftwich This study seeks to understand the fundamental fluid dynamic processes involved in human birth. We begin by examining the importance of amniotic fluid. This is done using two experimental techniques that approximate the laboring human uterus to different degrees of anatomical correctness. The first, in which a latex uterus is filled with fluid and a solid fetus is extracted, investigates the importance of both amniotic fluid properties and fetal position in the force required to remove a fetus. The second experiment simplifies the geometry of birth even more. In this case, a solid cylindrical rod is pulled through a highly flexible outer tube. The force to pull the inner cylinder as a function of the gap fluid properties is measured. By carefully controlling the fluid properties of the experiment, the study will provide further insight into the roles of amniotic fluid in human birth. [Preview Abstract] |
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