Bulletin of the American Physical Society
2009 APS March Meeting
Volume 54, Number 1
Monday–Friday, March 16–20, 2009; Pittsburgh, Pennsylvania
Session L15: Pattern Formation and Nonlinear Dynamics |
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Sponsoring Units: DFD Chair: Tom Solomon, Bucknell University Room: 316 |
Tuesday, March 17, 2009 2:30PM - 2:42PM |
L15.00001: Thermal Convection in the Presence of Internal Heating Gabriel Seiden, Stephan Weiss, Eberhard Bodenschatz Thermal convection in the presence of internal heat sources is an important mechanism of heat transfer in geophysics, particularly in planetary mantle convection. Carefully controlled laboratory studies of this mechanism are, however, scarce. We present experimental results on the effect of internal heating on Rayleigh-B\'{e}nard convection, where the heat sources are induced by IR absorption. The results are compared with available theoretical predictions. [Preview Abstract] |
Tuesday, March 17, 2009 2:42PM - 2:54PM |
L15.00002: Chaotic three particle dynamics in a viscous liquid filled rotating drum James E. Davidheiser, Eric R. Weeks, Phil Segre We conduct experiments to study the motions of three heavy spheres moving within a viscous liquid filled rotating cylindrical drum. Numerous works, in other geometries, demonstrated that assemblies of non-Brownian particles in viscous liquids have the potential to exhibit chaotic motion. We find that as the drum rotation rate $\omega$ is varied, there are several distinct periodic states as well as fully chaotic states. We track the motion of the spheres using a digital camera and custom particle tracking software. From our data, we characterize the chaotic trajectories as $\omega$ is varied. [Preview Abstract] |
Tuesday, March 17, 2009 2:54PM - 3:06PM |
L15.00003: Chaotic Dynamics of an Elastically Bouncing Dumbbell Colin Rees, Scott Franklin The dynamics of an elastically bouncing dumbbell is analogous to those of an ball bouncing on a sinusoidally oscillating surface with one important exception: the dumbbell's angular velocity, analogous to the surface's oscillation frequency, changes with each bounce, making the subsequent motion significantly more complicated. We investigate this dynamical system over a range of aspect ratios and initial energy, finding periodic, quasi-periodic and chaotic motions. As the initial energy is increased, the dumbbell can flip over and tumble. We find for large aspect ratios, however, narrow bands of energies well above this minimum where tumbling suddenly ceases. Because energy is conserved, the dynamics of a bounce are uniquely determined by the angle and angular velocity. The Lyapunov exponents of paths in this two dimensional phase space can be calculated, with the hope of identifying periodic islands within the chaotic sea. Finally, for certain parameters, the angle at each collision moves from its initial value in a subdiffusive manner, and we determine the characteristic exponents. [Preview Abstract] |
Tuesday, March 17, 2009 3:06PM - 3:18PM |
L15.00004: ABSTRACT WITHDRAWN |
Tuesday, March 17, 2009 3:18PM - 3:30PM |
L15.00005: Fixed point of a renormalization group approach for oscillator synchronization Tony Lee, Gil Refael, Michael Cross, Oleg Kogan, Jeffrey Rogers We apply a recently developed renormalization group method to a 1-dimensional chain of phase-coupled oscillators in the regime of weak randomness. The RG predicts how oscillators with randomly distributed frequencies and couplings form frequency-synchronized clusters. Although the RG was originally intended for strong randomness (distributions with long tails), we find good agreement with numerical simulations even in the regime of weak randomness. We also show analytically and numerically the existence of a stable fixed point in the functional RG space. At late stages of the RG, there is a universal approach to the fixed point regardless of the initial distributions of frequency and coupling. [Preview Abstract] |
Tuesday, March 17, 2009 3:30PM - 3:42PM |
L15.00006: Cell refinement and growing misorientations from a continuum dislocation density theory Yong Chen, Woosong Choi, Stefanos Papanikolaou, James P. Sethna, Surachate Limkumnerd At low temperatures, climb-free plastic deformation of crystals usually leads to the formation of cellular dislocation structures. Some experiments show fractal distributions of cell sizes; others show a single (non-fractal) characteristic cell size, but a scaling behavior of lengths and misorientations with external strain as the cellular structure refines. By adding an external growing stress field to a refined variant of our recently proposed wall-forming continuum dislocation dynamics theory \footnote{S. Limkumnerd and J. P. Sethna, Phys. Rev. Letters 96, 095503 (2006)}, we explore the formation and evolution of these cellular structures. We shall search both for the emergence of fractal geometries (in suitable experimental geometries) and for the emergence of scaling behaviors of misorientation angles and cell size distributions. [Preview Abstract] |
Tuesday, March 17, 2009 3:42PM - 3:54PM |
L15.00007: Dynamic self-assembly in far-from-equilibrium magnetic granular ensembles at the liquid/liquid interface Alexey Snezhko, Igor Aranson Magnetic particles suspended over an interface of two immiscible liquids and energized by a vertical alternating magnetic fields give rise to novel dynamic self-assembled structures (``pulsating magnetic stars,'' ``clams'') which are not accessible at the liquid/air interface. These novel structures is attributed to the interplay between surface waves, generated at the liquid/liquid interface by the collective response of magnetic microparticles to the alternating magnetic field, and hydrodynamic fields induced in the boundary layers of both liquids forming the interface. We show that while the onset of the dynamic self-assembly is controlled by the external driving magnetic field parameters the viscosity of the liquids forming the interface plays an essential role. Transition between different self-assembled structures with the parameters of the external excitations is observed. [Preview Abstract] |
Tuesday, March 17, 2009 3:54PM - 4:06PM |
L15.00008: Investigation on dynamics of colloidal particles with optically-controlled electrode patterns Kwan Hyoung Kang, Hyunjin Park, Horim Lee, Jiwoo Hong We investigated the dynamics of colloidal particles under ac electric fields. We used an optoelectronic substrate in which the conductivity of substrate can be changed optically. The shape of electrode pattern thus can be changed freely by controlling the optical pattern which is produced by a conventional projector. Interaction between particles showed a various patterns depending on applied electrical frequency, and rich dynamic characters are captured by dynamically changing the electrode pattern. Particle behaviors are in general governed by the balance between the dielectrophoresis and induced charge electroosmosis. [Preview Abstract] |
Tuesday, March 17, 2009 4:06PM - 4:18PM |
L15.00009: Memories in paste: their applications to control crack patterns Akio Nakahara, Yousuke Matsuo We experimentally find that a paste, i. e., a densely packed colloidal suspension with plasticity, has memories of external mechanical fields it suffered, such as flow and vibration. These memories are sustained as microscopically anisotropic network structures of colloidal particles. By drying these pastes, we find that the memories in pastes can be visualized as macroscopically anisotropic crack patterns. By using the memory effects of paste, we can imprint flow and vibration patterns into pastes to produce various crack patterns , such as lamellar, radial, ring, spiral, and so on [1]. [1] Physics Today 60 (2007), no. 9, p. 116. [Preview Abstract] |
Tuesday, March 17, 2009 4:18PM - 4:30PM |
L15.00010: Controlling chemical oscillations in heterogeneous BZ gels via mechanical strain. Victor Yashin, Krystyn J. Van Vliet, Anna C. Balazs We performed theoretical and computational studies to determine the effect of an applied mechanical strain on the dynamic behavior of heterogeneous polymer gels undergoing the oscillatory Belousov-Zhabotinsky (BZ) reaction. In these gels, the catalyst for the reaction is localized in specific patches within the polymer network and the BZ reaction only occurs within these BZ patches. We focused on a 1D model for the system, and considered two scenarios, in which the BZ reaction did or did not affect the degree of swelling within the gel. For gels having one and two BZ patches, we found that a longitudinal strain could induce transitions between the oscillatory and steady state regimes. For certain values of the BZ stoichiometric parameter $f$, these transitions could exhibit a hysteresis. In systems having two oscillating BZ patches, a strain could switch between the in-phase and out-of-phase synchronization of the oscillations. The ability to alter the dynamic behavior of BZ gels through mechanical deformations opens up the possibility of using these materials in novel chemo-mechanical sensors. [Preview Abstract] |
Tuesday, March 17, 2009 4:30PM - 4:42PM |
L15.00011: Rectification, Gating Voltage and Interchannel Communication of Nanoslot Arrays Due to Asymmetric Entrance Space Charge Polarization Gilad Yossifon, Yu-Chen Chang, Hsueh-Chia Chang A nanochannel array with homogenous surface charge and height (i.e. uniform electro-chemical potential) but with asymmetric channel separation at the entrances is shown to exhibit strong rectification and gating type I-V characteristics at large voltage. Unlike previous low-voltage Ohmic studies of ionic current rectification within nano-pores/channels, which is attributed to intrinsic non-uniformity of the electro-chemical potential along the nanochannel, the high-voltage rectification of asymmetric nanochannel array is due to asymmetric space-charge polarization and inter-channel communication at the entrances. This entrance polarization that controls the current flux at high voltages can overlap across nanochannels to render the array current very distinct from the collective current across isolated channels. [Preview Abstract] |
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