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 G33: Mini-Symposium: Complex Fluid Flows in Memory of Daniel D. Joseph I |
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Chair: Howard Hu, University of Pennsylvania Room: 29A |
Monday, November 19, 2012 8:00AM - 8:13AM |
G33.00001: Daniel D. Joseph, a Life in Fluid Dynamics James Feng I will give an overview of the remarkable career of Dan Joseph, and highlight the greatest contributions he has made to our discipline. [Preview Abstract] |
Monday, November 19, 2012 8:13AM - 8:26AM |
G33.00002: Loss of deformability of malaria-infected red blood cells S. Majid Hosseini, James Feng The pathogenesis of malaria is largely due to stiffening of the infected red blood cells (RBCs). Contemporary understanding ascribes the loss of RBC deformability to a 10-fold increase in membrane stiffness caused by extra cross-linking in the spectrin network. Local measurements by micropipette aspiration, however, have reported only an increase of ~3-fold in the shear modulus. We believe the discrepancy stems from the rigid parasite particles inside infected cells, and have carried out numerical simulations to demonstrate this mechanism. The cell membrane is represented by a set of discrete particles connected by linearly elastic springs. The cytosol is modeled as a homogeneous Newtonian fluid, and discretized by particles as in standard smoothed particle hydrodynamics. The malaria parasite is modeled as an aggregate of particles constrained to rigid-body motion. We simulate RBC stretching tests by optical tweezers in three dimensions. The results demonstrate that the presence of a sizeable parasite greatly reduces the ability of RBCs to deform under stretching. With the solid inclusion, the observed loss of deformability can be predicted quantitatively using the local membrane elasticity measured by micropipettes. [Preview Abstract] |
Monday, November 19, 2012 8:26AM - 8:52AM |
G33.00003: Thermal convection, energy stability theory, viscous fingering, and capillary attraction: a 40 year interaction with Dan Joseph G.M. Homsy Dan Joseph made major contributions to all the topics in the title. These topics are also areas of interaction between Dan and the speaker that began in 1969 and continued for 40+ years. This talk will report on our recent work on capillary attraction between floating particles and, as time allows, will include some reminiscences. [Preview Abstract] |
Monday, November 19, 2012 8:52AM - 9:18AM |
G33.00004: Some surprising results on convective transport in the Sun Katepalli Sreenivasan, Shravan Hanasoge, Thomas Duvall, Jr. Convection in the interior of our Sun comprises structures on a wide spectrum of scales. The dynamical parameters relevant to the problem cannot be replicated in laboratory experiments or numerical simulations, so our understanding of these observed features is quite incomplete even at the phenomenological level. We analyze observations of the wavefield in solar photosphere using techniques of time-distance helioseismology to deduce flows in the solar interior. We downsample and synthesize 900 billion wavefield observations to produce 3 billion cross-correlations, which we average and fit, measuring 5 million wave travel times. Using these travel times, we deduce the underlying flow systems and study their statistics to bound convective velocity magnitudes in the solar interior, as a function of depth and spherical-harmonic degree. We find the convection velocities so deduced to be 20-100 times weaker than suggested by current theoretical estimates. This result indicates the prevalence of a different paradigm of turbulence from that predicted by existing models, prompting the question: what mechanism transports the heat flux of a solar luminosity outwards? We cast our results in terms that should be particularly relevant to turbulent transport in convective systems with rotation. [Preview Abstract] |
Monday, November 19, 2012 9:18AM - 9:44AM |
G33.00005: Forming adjustable monolayers via particle assembly at electrified liquid-fluid interfaces Nadine Aubry, Pushpendra Singh, Muhammad Janjua, Sai Nudurupati The application of an external electric field leads to the assembly of particles at a liquid-fluid interface into monolayers which display long-range order and whose spacing between the particles can be adjusted by varying the strength and/or frequency of the electric field. In contrast to capillarity induced self-assembly, the technique permits the assembly of \textit{small }particles, i.e., submicron to nano sized particles. This is possible because (i) the particles experience electric field induced capillary forces and (ii) the associated energy of such forces is greater than kT. The adjustment of the lattice spacing, and therefore the control of the mechanical, thermal, optical properties of the monolayer, is achieved through a judicious combination of attractive capillary forces and repulsive particle-particle interactions which is realized in practice by varying the electric field. [Preview Abstract] |
Monday, November 19, 2012 9:44AM - 10:10AM |
G33.00006: Dan Joseph's contributions to disperse multiphase flow Andrea Prosperetti During his distinguished career, Dan Joseph worked on a vast array of problems. One of these, which occupied him off and on over the last two decades of his life, was that of flows with suspended finite-size particles at finite Reynolds numbers. He realized early on that progress in this field had to rely on the insight gained from numerical simulation, an area in which he was a pioneer. On the basis of the early numerical results he recognized the now famous ``drafting, kissing and tumbling'' mechanism of particle-particle interaction, the possibility of fluidization by lift and many others. With a number of colleagues and a series of gifted students he produced a significant body of work summarized in his on-line book {\em Interrogations of Direct Numerical Simulation of Solid-Liquid Flows} available from {\tt http://www.efluids.com/efluids/books/joseph.htm}. This presentation will describe Joseph's contribution to the understanding of disperse multiphase flow and conclude with some examples from the author's recent work in this area. [Preview Abstract] |
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