Bulletin of the American Physical Society
68th Annual Meeting of the APS Division of Fluid Dynamics
Volume 60, Number 21
Sunday–Tuesday, November 22–24, 2015; Boston, Massachusetts
Session L41: Russell Donnelly Minisymposium |
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Chair: K.R. Sreenivasan, New York University Room: Sheraton Constitution A |
Monday, November 23, 2015 4:05PM - 4:18PM |
L41.00001: Russell Donnelly at Chicago Invited Speaker: Leo Kadanoff The period (1956-1965) in which Russ served as a faculty member at Chicago was one in which he set the main topics that occupied his subsequent professional life. These included the few-degree Helium work that formed the low temperature physics of that period. This work included studies of motion of vortex lines and ions in Helium. During that period, he had seven doctoral students mostly devoted in work in these areas. In addition he served as a good citizen of both his department and his field of science, by publishing a book on ``Experimental Superfluidity'' based on course lecture notes and also serving as an editor of a conference volume on ``Non-equilibrium Thermodynamics.'' Because of the University of Chicago's nepotism rules, Russ's wife could not follow her academic interests here. They both left for the University of Oregon. [Preview Abstract] |
Monday, November 23, 2015 4:18PM - 4:31PM |
L41.00002: An Instability in Stratified Taylor-Couette Flow Invited Speaker: Harry Swinney In the late 1950s Russell Donnelly began conducting experiments at the University of Chicago on flow between concentric rotating cylinders, and his experiments together with complementary theory by his collaborator S. Chandrasekhar ({\it Hydrodynamic and Hydromagnetic Stability}, Clarendon Press, 1961) did much to rekindle interest in the flow instability discovered and studied by G.I. Taylor (1923). The present study concerns an instability in a concentric cylinder system containing a fluid with an axial density gradient. In 2005 Dubrulle et al. suggested that a `stratorotational instability' (SRI) in this system could provide insight into instability and angular momentum transport in astrophysical accretion disks ({\it Astron. Astrophys.} {\bf 429}, 429). In 2007 the stratorotational instability was observed in experiments by Le Bars and Le Gal ({\it Phys. Rev. Lett.} {\bf 99}, 064502). We have conducted an experiment on the SRI in a concentric cylinder system (radius ratio $\eta =0.876$) with buoyancy frequency $N/2\pi=$ 0.25, 0.50, or 0.75 Hz. For $N$ = 0.75 Hz we observe the SRI onset to occur for $\Omega_{outer}/\Omega_{inner} > \eta$, contrary to the prediction of Shalybkov and R\"udiger ({\it Astron. Astrophys.} {\bf 438}, 411, 2005). [Preview Abstract] |
Monday, November 23, 2015 4:31PM - 4:44PM |
L41.00003: Expanding Participation in Fluid Dynamics Research Invited Speaker: Randall Tagg Two legacies provided by great scientists are scientific discoveries and more scientists. Is there a way that these impacts can be magnified? Examples using the Taylor-Couette experiment and other fluid dynamics problems will demonstrate that indeed more people can fruitfully engage in open and even bold investigation. Participants include high school students, teachers, undergraduates, artists, business developers and interested laypersons. With imagination, good training, and a suitable lab space, a special tribute can be given to those who mentor us by scaling up the breadth of their influence. [Preview Abstract] |
Monday, November 23, 2015 4:44PM - 4:57PM |
L41.00004: Russ Donnelly's research at the University of Oregon Invited Speaker: Joseph Niemela Coming to the University of Oregon in 1966, Russ Donnelly built up a strong research activity having two threads within hydrodynamics: the flow of ordinary fluids and that of superfluids. Vortices—quantized and classical—were at the heart of his research. His 1991 book “Quantized Vortices in Helium II,” by now a standard reference for researchers and students, elucidated some of it. To produce vortices Russ brought from Chicago two enormous rotating tables, based on 1-m diameter industrial lathe chucks obtained from General Motors. They were also used for classical systems such as Taylor-Couette flow (to generate strong Coriolis forces) and thermal convection, where the properties of rotation—including early experimental investigations of the Kuppers-Lortz instability—were studied. Another common thread in his research was the modulation of control parameters leading to Stokes layer effects, both thermal and viscous. In the early ‘90s, Russ and his group turned their attention to cryogenic turbulence in normal and superfluid systems, creating what has now become a small industry and a well-established sub-field within low temperature physics. [Preview Abstract] |
Monday, November 23, 2015 4:57PM - 5:10PM |
L41.00005: Turbulent convection at high Rayleigh numbers Invited Speaker: Guenter Ahlers Russ Donnelly had a vision of building a ten-meter tall Rayleigh-B\'enard convection cell for use at helium temperatures at one of the high-energy physics facilities with very large helium liquefaction capacity. It would have reached Rayleigh numbers in the $10^{20}$ range and had the promise of yielding detailed information about the so-called ultimate state of turbulent convection which is highly relevant to many geophysical and astrophysical problems as well as to oceanography and climate physics. Although this was not to happen for reasons beyond his control, a laboratory-sized precursor of this venture yielded data for $Ra$ up to $10^{17}$. $^{3}$ The results were interpreted to yield no definitive indication of a transition to the ultimate state. This talk will review some of these data and compare them with more recent measurements using SF$_6$ at ambient temperatures and high pressure. $^4$ This comparison suggests that the Donnelly group actually entered a transition range to the ultimate state near $Ra_1^* \simeq 6\times 10^{12}$, but re-entered the classical state at larger $Ra$ because with increasing $Ra$ the Prandtl number (which affects $Ra^*_1$) also increased in those experiments. In view of the above, one can estimate that, for the same parameter values, the originally envisioned ten-meter cell could have yielded a range of a couple of decades of $Ra$ in the ultimate state. \newline \vskip 0.05in \noindent 3.) J. J. Niemela, L. Skrbek, K. R. Sreenivasan, and R. J. Donnelly, Nature {\bf 404}, 837 (2000). \newline \noindent 4.) G. Ahlers, X. He, D. Funfschilling, and E. Bodenschatz, New J. Phys. {\bf 14}, 103012 (2012). [Preview Abstract] |
Monday, November 23, 2015 5:10PM - 5:23PM |
L41.00006: Czech cryogenic fluid dynamics inspired by Russ Donnelly Invited Speaker: Ladislav Skrbek Following nearly five years of work along with Russ in Eugene on cryogenic turbulent convection and quantum grid turbulence, two laboratories in Prague and in Brno have been established to continue experimental research in cryogenic fluid dynamics using all three forms of cryogenic 4He - cold helium gas, normal liquid He I and superfluid He - as excellent multi-purpose working fluids. We review some of our investigations of very high Rayleigh number cryogenic thermal convection and classical and quantum turbulence in liquid helium. In particular, we discuss heat transfer efficiency of turbulent Rayleigh-Benard convection and the role of non-Oberbeck-Boussinesq conditions on possible transition to its ultimate regime; our second sound attenuation experiments probing both steady state and decaying coflow, counterflow and pure superflow of He II through channels of square cross-section including the concept of effective kinematic viscosity. We then introduce visualization experiments of classical and quantum flows of liquid helium using micron-size hydogen/deuterium particles and our recent results on transition to quantum turbulence based on the revisited experiments with a torsionally oscillating disc. [Preview Abstract] |
Monday, November 23, 2015 5:23PM - 5:36PM |
L41.00007: Quantised vortices in polariton lattices Invited Speaker: Natalia Berloff The first comprehensive treatment of quantised vorticity in the light of research on vortices in modern fluid mechanics appeared in Russell Donnelly seminal research papers and summarized in his 1991 book ``Quantized Vortices in Helium II''. Recently quantized vortices have been studied in polariton condensates. Polaritons are the mixed light-matter quasi-particles that are formed in the strong exciton-photon coupling regime. Under non-resonant optical excitation rapid relaxation of carriers and bosonic stimulation result in the formation of a non-equilibrium polariton condensate characterized by a single many-body wave-function, therefore, naturally possessing quantized vortices. Polariton condensates can be imprinted into any two-dimensional lattice by spatial modulation of the pumping laser and form vortices via interacting outfows from the pumping sites. Optically pumped polariton condensates can be injected in lattice configurations with arbitrary density profiles offering the possibility to control the kinetics of the condensate and therefore the number and location of vortices. I will present some new developments in theoretical and experimental studies of quantized vortices in polariton condensates and discuss possible practical implementations of polariton lattices. [Preview Abstract] |
Monday, November 23, 2015 5:36PM - 5:49PM |
L41.00008: Visualization in quantum fluids Invited Speaker: Daniel Lathrop The motion of quantized vortices, which are topological phase defects analogous to crystalline dislocations, substantially controls the dynamics of quantum fluids. Quantized vortices have been observed in superfluid 4He and AMO trapped atom systems, and have been inferred in superfluid 3He and neutron stars. Long-range quantum order underlies a number of related physical phenomena, including superfluidity, trapped-atom Bose-Einstein condensates, superconductivity, ferromagnetism, anti-ferromagnetism, lasers, and the Higgs mechanism. While superfluidity in 4He is one of the first discovered of these phenomena, it is one of the least understood, given that the strongly interacting nature of helium makes theory difficult, and that development of local experimental probes is lagging. The advent of flow visualization of particles that trace quantized vortices has led to many advances. That progress was caused by repeated suggestions from Russ Donnelly, Joe Niemela, and Joe Vinen. Those suggestions led the team, including Gregory P. Bewley, K.R. Sreenivasan and myself, to venture into the quantum fluid realm. [Preview Abstract] |
Monday, November 23, 2015 5:49PM - 6:02PM |
L41.00009: Direct and inverse energy transfers in superfluid turbulence Invited Speaker: Carlo Barenghi Three dimensional isotropic homogeneous turbulence is characterized by a direct cascade of energy from large to small length scales. A reversed flux of energy from small to large length scales is observed in two dimensional turbulence, and, in three dimensions, in the presence of strong anisotropy, rotation or stratification. Biferale et al. (2012) demonstrated that the three dimensional inverse cascade arises by artificially restricting the nonlinearity of the Navier-Stokes equation to the interaction of helical modes of the same sign; they concluded that all three dimensional flows contain nonlinearities which may lead to an inverse cascade, but one has to break the mirror symmetry of the interactions. In superfluid helium at very low temperature the nature of turbulence is particularly simple: the flow is inviscid and the vorticity is constrained to thin, quantum vortex filaments of atomic thickness which interact with each according to the classical Euler equation; unlike classic Euler vortices, due to their quantum nature, superfluid vortices undergo reconnection events when they approach each other by a distance of the order of the vortex core thickness. Recent experimental, theoretical, and numerical studies have demonstrated evidence of the direct energy cascade in superfluid turbulence. In this work we show that in superfluid turbulence the more subtle inverse energy transfer described by Biferale et al. can be directly understood in physical space from the geometry of reconnecting vortex filaments, and argue that the effect has been detected in experiments with liquid helium. [Preview Abstract] |
Monday, November 23, 2015 6:02PM - 6:15PM |
L41.00010: Russell Donnelly's last legacy: Pursuing grid turbulence in superfluid $^{4}$He Gary Ihas, Jihee Yang Quantum turbulence, a tangle of quantized vortex lines in a superfluid, may hold significant keys to understanding all types of turbulence. Russell Donnelly pioneered this line of research, beginning with studies of grid turbulence probed by second sound.\footnote{M. R. Smith, R. J. Donnelly, N. Goldenfeld, and W. F. Vinen, Phys. Rev. Lett. 71, 2583 (1993); S. R. Stalp, Ph.D. dissertation, University of Oregon (1998).} The apparatus built by Russell and his students, with significant up-grades, is now being used at the University of Florida to continue his work on decaying grid turbulence in superfluid $^{4}$He. The Oregon work used a 1cm wide square channel, while the Florida work has been in both 1 cm and 5 cm square channels. The larger channel allows detailed study of the increase in eddy size before saturation at the channel walls during the decay process. Power law fits of the turbulence decay in time allow comparison with theory, work intended to be Russell Donnelly's last experiment. [Preview Abstract] |
Monday, November 23, 2015 6:15PM - 6:28PM |
L41.00011: Decaying turbulence at the laminar-turbulence transition in a pipe Nigel Goldenfeld, Tsung-Lin Hsieh, Hong-Yan Shih As a follow-up to Donnelly's pioneering research on the decay of superfluid turbulence in a pipe, we have studied a different regime: transitional turbulence. Near the onset to turbulence in a pipe, turbulent puffs decay either directly or through splitting, with characteristic time-scales that exhibit a super-exponential dependence on Reynolds number. Using direct numerical simulations of transitional pipe flow, we show that a collective mode, a so-called zonal flow emerges at large scales, activated by anisotropic turbulent fluctuations, as measured in terms of Reynolds stress. This zonal flow imposes a shear on the turbulent fluctuations that tends to suppress their anisotropy, leading to stochastic oscillatory dynamics. These results motivate the proposal that the laminar-turbulence non-equilibrium phase transition can be modeled by an effective theory, usefully thought of as predator-prey dynamics, leading to a predicted universality class of directed percolation. [Preview Abstract] |
Monday, November 23, 2015 6:28PM - 6:41PM |
L41.00012: Granular materials and their connection to Russell Donnelly Invited Speaker: Bob Behringer I have known Russell Donnelly for most of my professional career. Our interests in liquid helium, in fluid dynamics and instabilities, the use of helium to study convection, are all points of significant overlap. Trying to decide when I first met Russ is hard, so let me focus on one year, 1996. That year Russ came to Duke to give the Fritz London Memorial Lecture. It was also a year that I remember because the DFD meeting at Syracuse had a large number of talks dealing with granular materials. I first became interested in this field as a system to test for hydrodynamic-like instabilities. Russ had been a strong supporter of including granular flows inDFD meetings, and the field was well on its way in 1996. In fact, the predicted instability was not there, but many striking and novel phenomena were: interest in the physics of granular materials has grow dramatically since then. In this talk, I will explore some of the roots of granular physics and the connections to fluid flows.In particular, flowing grains show surprising fluctuations in forces that are tied to novel structures known as force chains. These structures also play a key role in how granular materials become ``solids,'' i.e. jam. The idea of jamming arose in early work by M. Cates et al. and by A. Liu and S. Nagel. We have recently shown that the nature of jamming is fundamentally changed when the grains have friction or shape, which are general properties of grains that form many everyday materials. In general, understanding how granular materials transition between jammed or unjammed draws substantially on statistical physics--something that would have strongly appealed to Russ. [Preview Abstract] |
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