Bulletin of the American Physical Society
65th Annual Meeting of the APS Division of Fluid Dynamics
Volume 57, Number 17
Sunday–Tuesday, November 18–20, 2012; San Diego, California
Session D15: Biofluids: Large Swimmers I |
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Chair: Ellen Longmire, University of Minnesota Room: 28A |
Sunday, November 18, 2012 2:15PM - 2:28PM |
D15.00001: Dynamics of a self-propelled undulating swimmer Sophie Ramananarivo, Maxime Dana, Benjamin Thiria, Ramiro Godoy-Diana Undulatory propulsion is a mean of locomotion shared by living organisms over a wide range of scales and in many different media. From eels to spermatozoa or motile bacteria, net forward motion is achieved by propagating backward, actively or passively, elastic waves along a deformable body. Here, we use a simple yet versatile experiment that constitutes a good framework to study the dynamics of undulatory swimmers. The set-up consists in a flexible filament forced to oscillate by imposing a harmonic motion to one of its extremities, and propelling itself at the free surface of a water tank. The present experiments pertain to the inertial regime for which Lighthill's elongated-body theory is the reference theoretical framework. We fully characterize the nature of the wave travelling the filament to understand the changes in the propulsive performance encountered in this inertial regime. We analyze in particular the role of the spatial envelope of the elastic wave, which is crucial in the present experiment where the oscillation of the filament is driven at the head of the swimmer and the deformation of the tail is passive. [Preview Abstract] |
Sunday, November 18, 2012 2:28PM - 2:41PM |
D15.00002: Fluid dynamics of forward swimming and turning for jellyfish Laura Miller Jellyfish propel themselves through the water through periodic contractions of their elastic bells. Some jellyfish, such as the box jellyfish Tripedalia cystophora and the upside down jellyfish Cassiopea xamachana, can perform turns via asymmetric contractions of the bell and by generating asymmetries in the outflow opening of the bell. The fluid dynamics of jellyfish forward propulsion and turning is explored here using the immersed boundary method. The 2D and 3D Navier-Stokes equations are coupled to the motion of a simplified jellyfish represented by an elastic boundary. An adaptive and parallelized version of the immersed boundary method (IBAMR) is used to resolve the detailed structure of the vortex wake. The asymmetric contraction and structure of the jellyfish generates asymmetries in the starting and stopping vortices. This creates a diagonal jet and a net torque acting on the jellyfish. [Preview Abstract] |
Sunday, November 18, 2012 2:41PM - 2:54PM |
D15.00003: Learning from real and tissue-engineered jellyfish: How to design and build a muscle-powered pump at intermediate Reynolds numbers Janna Nawroth, Hyungsuk Lee, Adam Feinberg, Crystal Ripplinger, Megan McCain, Anna Grosberg, John Dabiri, Kit Parker Tissue-engineered devices promise to advance medical implants, aquatic robots and experimental platforms for tissue-fluid interactions. The design, fabrication and systematic improvement of tissue constructs, however, is challenging because of the complex interactions of living cell, synthetic materials and their fluid environments. In a proof of concept study we have tissue-engineered a construct that mimics the swimming of a juvenile jellyfish, a simple model system for muscle-powered pumps at intermediate Reynolds numbers with quantifiable fluid dynamics and morphological properties. Optimally designed constructs achieved jellyfish-like swimming and generated biomimetic propulsion and feeding currents. Focusing on the fluid interactions, we discuss failed and successful designs and the lessons learned in the process. The main challenges were (1) to derive a body shape and deformation suitable for effective fluid transport under physiological fluid conditions, (2) to understand the mechanical properties of muscle and bell matrix and device a design capable of the desired deformation, (3) to establish adequate 3D kinematics of power and recovery stroke, and (4) to evaluate the performance of the design. [Preview Abstract] |
Sunday, November 18, 2012 2:54PM - 3:07PM |
D15.00004: Viscous flow around a rapidly collapsing cylinder as a model of animal locomotion Gabriel Weymouth, Michael Triantafyllou A large body of experimental research indicates that shape change is instrumental in the locomotion of many animals from basilisk lizards to swifts and ducks. As a two dimensional model of such body shape changes, we examine the changes in force, energy, and vorticity induced by two manners of rapidly reduced cylinders; a ``deflating'' cylinder with prescribed kinematics, versus a prescribed ``melting'' cylinder similar to the problem of the vanishing disk considered by Taylor in 1953. Using large-scale viscous flow simulations, we show that the dynamics of the two cases generate fundamentally different flow fields. The deflating cylinder practically erases the memory of the original larger cylinder flow, with the excess kinetic energy being recovered at the body boundary, and opposite-sign vorticity cancels the excess boundary layer vorticity. In contrast, the melting cylinder case shows instantaneous and global shedding of the vorticity, which rapidly form into two strong vortices that contain the excess kinetic energy. Both the shrinking and melting body conditions are then used to demonstrate the effect of shape changing appendages in a set of simple two-dimensional maneuvering problems. [Preview Abstract] |
Sunday, November 18, 2012 3:07PM - 3:20PM |
D15.00005: ABSTRACT WITHDRAWN |
Sunday, November 18, 2012 3:20PM - 3:33PM |
D15.00006: A Three-Dimensional Multi-Domain Immersed Boundary Method, with Application to a Pitching Wing Chengjie Wang, Jeff D. Eldredge A three-dimensional multi-domain technique and immersed boundary projection method is implemented for high-fidelity solution of the Navier-Stokes equations based on the approach presented by Colonius and Taira (2008). The principle of the multi-domain approach is to derive the boundary condition on a given domain from the interpolation of the solution on a larger, but coarser, mesh to simulate the unbounded flow. By performing this on a progression of such domains, the resulting flow in the original (finest) domain, which may contain some bodies, is able to account for the effect from the vorticity that is far away from it. On the other hand, the computational requirement is significantly relaxed compared to that of a single monolithic domain due to the compactness of each domain in the hierarchy, and the overall performance of the scheme is improved. The governing equations, and the immersed boundary treatment, are expressed in vorticity-streamfunction form. The resulting scheme is used to explore the physics of a low-aspect-ratio pitching wing in Re=100 flow. A wing of rectangular planform of aspect ratio 2 undergoes a steady pitch-up from 0 to 90 degrees in a uniform flow. Results for different pitching rate are compared and discussed. [Preview Abstract] |
Sunday, November 18, 2012 3:33PM - 3:46PM |
D15.00007: Modeling an elastic swimmer driven at resonance Peter Yeh, Alexander Alexeev Flexibility plays a vital role in the locomotion of aquatic animals. Using three dimensional computer simulations, we examine a flexible swimmer submerged in a viscous fluid with Reynolds number 100. The swimmer is modeled as a thin elastic rectangular plate, actuated at its leading edge to oscillate in a sinusoidal motion vertically at constant frequency and amplitude. The Lattice Boltzmann model is used to simulate an incompressible viscous fluid. The swimmer is free to move horizontally, and we measure the resulting steady state forward velocity, input power, and swimming performance. Our calculations reveal that both steady swimming velocity and performance strongly depend on the actuated frequency. Specifically, the maximum forward velocity is achieved near resonance, but the performance is maximized at a frequency about 1.8 times that at resonance. We visualize the vortex structures emerging in the fluid around swimmer and show how they contribute to the swimmer's forward motion. [Preview Abstract] |
Sunday, November 18, 2012 3:46PM - 3:59PM |
D15.00008: Applying IR Tomo PIV and 3D Organism Tracking to Study Turbulence Effects on Oceanic Predator-Prey Interactions Deepak Adhikari, Michael Hallberg, Brad Gemmell, Ellen Longmire, Edward Buskey The behavorial response of aquatic predators and prey depends strongly on the surrounding fluid motion. We present a facility and non-intrusive instrumentation system designed to quantify the motions associated with interactions between small coral reef fish (blennies) and evasive zooplankton prey (copepod) subject to various flow disturbances. A recirculating water channel facility is driven by a paddlewheel to prevent damaging the zooplankton located throughout the channel. Fluid velocity vectors surrounding both species are determined by time-resolved infrared tomographic PIV, while a circular Hough transform and PTV technique is used to track the fish eye in three-dimensional space. Simultaneously, zooplankton motions are detected and tracked using two additional high-speed cameras with IR filters. For capturing larger scales, a measurement volume of 80 x 40 x 18 mm is used with spatial resolution of 3.5 mm. For capturing smaller scales, particularly for observing flow near the mouth of the fish during feeding, the measurement volume is reduced to 20 x 18 x 18 mm with spatial resolution of 1.5 mm. Results will be presented for both freshwater and seawater species. [Preview Abstract] |
Sunday, November 18, 2012 3:59PM - 4:12PM |
D15.00009: Quantitative analysis of the role of symmetry in biomimetic propulsive wakes Veronica Raspa, Ramiro Godoy-Diana, Benjamin Thiria We address here the understanding of how animal propulsion is related to flow physics in biomimetic locomotion. It is known that the wake pattern observed in a cross-section behind swimming or flying animals is typically characterized by the presence of periodical vortex shedding. However, depending on species, propulsive wakes are distinguished by their spatial ordering: symmetric (squid-like) or asymmetric (fish-like), with respect to the motion axis. We conducted a very precise experiment to analyse the role of the wake topology in propulsion generation. Self-propulsion is achieved by the flapping motion of two identical pitching rigid foils, separated by a distance $d$. By keeping the momentum input unchanged, we compared both symmetric and asymmetric flapping modes. For the entire parameters range, the symmetric squid-like mode proves to be more efficient for thrust generation than the fish-like asymmetrical one. We show that this difference is due to a pressure effect related to the ability of each wake to produce, or not, significant mixing in the near wake region. [Preview Abstract] |
Sunday, November 18, 2012 4:12PM - 4:25PM |
D15.00010: Effect of longitudinal ridges on the aerodynamic performance of a leatherback turtle model Kyeongtae Bang, Jooha Kim, Heesu Kim, Sang-Im Lee, Haecheon Choi Leatherback sea turtles ($Dermochelys$ $coriacea$) are known as the fastest swimmer and the deepest diver in the open ocean among marine turtles. Unlike other marine turtles, leatherback sea turtles have five longitudinal ridges on their carapace. To investigate the effect of these longitudinal ridges on the aerodynamic performance of a leatherback turtle model, the experiment is conducted in a wind tunnel at $Re$ = 1.0 $\times$ $10^5$ -- 1.4 $\times$ $10^6$ (including that of real leatherback turtle in cruising condition) based on the model length. We measure the drag and lift forces on the leatherback turtle model with and without longitudinal ridges. The presence of longitudinal ridges increases both the lift and drag forces on the model, but increases the lift-to-drag ratio by 15 -- 40\%. We also measure the velocity field around the model with and without the ridges using particle image velocimetry. More details will be shown in the presentation. [Preview Abstract] |
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