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 L18: Biofluids: General V |
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Chair: Jiarong Hong, University of Minnesota Room: 306/307 |
Monday, November 25, 2013 3:35PM - 3:48PM |
L18.00001: The Hydrodynamics and Odorant Transport Phenomena of Olfaction in the Hammerhead Shark Alex Rygg, Brent Craven The hammerhead shark possesses a unique head morphology that is thought to facilitate enhanced olfactory performance. The olfactory organs, located at the distal ends of the cephalofoil, contain numerous lamellae that increase the surface area for olfaction. Functionally, for the shark to detect chemical stimuli, water-borne odors must reach the olfactory sensory epithelium that lines these lamellae. Thus, odorant transport from the aquatic environment to the sensory epithelium is the first critical step in olfaction. Here we investigate the hydrodynamics and odorant transport phenomena of olfaction in the hammerhead shark based on an anatomically-accurate reconstruction of the head and olfactory chamber from high-resolution micro-CT and MRI scans of a cadaver specimen. Computational fluid dynamics (CFD) simulations of water flow in the reconstructed model reveal the external and internal hydrodynamics of olfaction during swimming. Odorant transport in the olfactory organ is investigated using a multi-scale approach, whereby molecular dynamics (MD) simulations are used to calculate odorant partition coefficients that are subsequently utilized in macro-scale CFD simulations of odorant deposition. The hydrodynamic and odorant transport results are used to elucidate several important features of olfactory function in the hammerhead shark. [Preview Abstract] |
Monday, November 25, 2013 3:48PM - 4:01PM |
L18.00002: An Experimental Study of Flow Separation Control by Shortfin Mako Shark Skin Farhana Afroz, Amy Lang, Philip Motta, Maria Habegger The shortfin mako shark (Isurus oxyrinchus) is a fast swimmer and has incredible turning agility. Shark skin is covered with flexible scales and this bristling capability may result in a unique Boundary Layer Control (BLC) method to reduce drag. It is hypothesized that scales bristle when the flow above it is reversed, and between the bristled scales embedded micro-vortices form in the cavities which induce boundary layer mixing and aid in delaying flow separation. To testify this hypothesis, samples of mako shark skin have been tested in a water tunnel under various strengths of adverse pressure gradient (APG). Laminar and turbulent separation over shark skin was studied experimentally using Time-Resolved Digital Particle Image Velocimetry (TR-DPIV) system, where the APG was generated and varied using a rotating cylinder. Then shark skin results were compared with that of a flat plate data for a given amount of APG. The study reveals that shark skin is capable of controlling both laminar and turbulent flow separation. [Preview Abstract] |
Monday, November 25, 2013 4:01PM - 4:14PM |
L18.00003: 3D flow investigation near the denticles of biomimetic shark skin model using Digital In-line Holographic Microscopy Mostafa Toloui, Jiarong Hong It has been hypothesised that the complex microscopic denticles on a shark skin reduce the total drag for a swimming shark. However, the fundamental mechanism of this hydrodynamic function is not fully understood due to the inability to reproduce the complex shark surface and resolve the detailed flow around the skin denticles. Here we report a preliminary experiment using a 3D printed transparent rough surface replicating the morphological features of real shark skin. The model skin consists of closely-packed denticles of 2 mm in scale, i.e. $\sim$ 10 times of the real size. Particle image velocimetry based on digital in-line holography is employed to measure 3D flow structures. To reduce optical abberration and enable imaging around the denticles, we use a fluid medium that has the same optical refractive index as that of the skin model. The experiment is conducted in 2''x2'' square channel at a moderate Re number matching the general flow around a cruising shark. Several samples of the 3D velocity field amid and above the denticles are obtained. The follow-up research envisions a large dataset of these samples over the rigid/deformable model operated in stationary/undulating mode to ellucidate the dominant flow structures generated by the denticals. [Preview Abstract] |
Monday, November 25, 2013 4:14PM - 4:27PM |
L18.00004: Shortfin Mako Skin: A Possible Passive Flow Control Mechanism for Drag Reduction Jennifer Wheelus, Amy Lang, Michael Bradshaw, Phillip Motta, Maria Habegger The shortfin mako is one of the fastest and most agile ocean predators creating the need to minimize its pressure drag by controlling flow separation. One proposed method for flow control is the activation of small teeth-like denticles, on the order of 0.2 mm, that cover the skin of the shark. Biological studies of the shortfin mako skin have shown the passive bristling angle of their denticles to exceed 50 degrees in areas on the flank corresponding to the locations likely to experience separation first. It is proposed that reversing flow, as occurs at the onset of separation in a turbulent boundary layer, would activate denticle bristling and hinder local separation from leading to global separation over the shark. It has been shown on a biomimetic model that bristled denticles create cavities that support the formation of vortices that interact with the boundary layer. This interaction is thought to support momentum exchange and allow the flow to stay attached longer. This experiment focuses on the mechanism that triggers bristling of the real shark skin denticles and further explores the interaction those denticles foster with the boundary layer on a 3D biomimetic model using Digital Particle Image Velocimetry (DPIV). [Preview Abstract] |
Monday, November 25, 2013 4:27PM - 4:40PM |
L18.00005: Optimal lamellar arrangement in fish gills Keunhwan Park, Wonjung Kim, Ho-Young Kim We present the results of a combined theoretical and experimental investigation of the oxygen transport in fish gills. Efficient respiration is crucial to fish because of relatively low oxygen contents in water compared to that in air. Ordered structures of lamellae of fish gills offer extended surfaces for oxygen transport. While the more compact arrangement of the lamellae provides larger surface area for oxygen diffusion, it causes higher viscous resistance to water flow through the interlamellar space. This allows us to expect the optimal lamellar arrangement for maximizing the oxygen transport. By developing a dynamic model for oxygen transport in fish gills, we calculate optimal lamellar arrangement for maximizing oxygen transport. We demonstrate that the interlamellar distance of a broad range of fish species is consistent with the deduced optimal lamellar arrangement. Our results thus provide the first rationale for the relatively uniform interlamellar distance of many fish regardless of their size, appearance, and habitat. [Preview Abstract] |
Monday, November 25, 2013 4:40PM - 4:53PM |
L18.00006: Viscous-elastic interaction as a mechanism to create adhesion in frogs' toe pads Amir Gat, Arie Tulchinsky The toe pads of frogs consist of soft hexagonal structures and a network of channels between and within the soft structures, containing a viscous liquid. It has been hypothesized that this configuration creates adhesion by allowing for long range capillary forces, or alternatively, that the channel network allows for exit of the viscous liquid and thus improve contact of the toe pad. In this work we suggest interaction between viscous flow and elastic forces as a mechanism to create temporary adhesion, even in the absence of capillary or van der Waals forces. We study the dynamics of a solid body covered with an array of protruding elastic cylinders, immersed within a viscous liquid, and pressed against a flat surface. Inertia is neglected and the elastic-viscous dynamics yield the governing differential equation describing the relative motion between the body and the surface. The compressed elastic cylinders apply a force acting to separate the solid body from the surface. The relative motion between the body and the surface creates a viscous flow and pressure field resisting the elastic force and significantly reducing the speed of separation. We show that the viscous-elastic interaction can prevent motion tangential and normal to the surface and can create temporary adhesion. [Preview Abstract] |
Monday, November 25, 2013 4:53PM - 5:06PM |
L18.00007: The Hawaiian bobtail squid as a model system for selective particle capture in microfluidic systems. Janna Nawroth, Margaret McFall-Ngai, John Dabiri Juvenile Hawaiian bobtail squids reliably capture and isolate a single species of bacteria, Vibrio fischeri, from inhaled coastal water containing a huge background of living and non-living particles of comparable size. Biochemical mechanisms orchestrate a chain of specific interactions as soon as V.fischeri attach to the squid's internal light organ. It remains unclear, however, how the bacteria carried by the squid's ventilation currents are initially attracted to the light organ's surface. Here we present preliminary experimental data showing how arrangement and coordination of the cilia covering the light organ create a 3D flow field that facilitates advection, sieving and selective retention of flow-borne particles. These studies may inspire novel microfluidic tools for detection and capture of specific cells and particles. [Preview Abstract] |
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