Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session S12: Transitional Flows and Non-linear Dynamics IIRecordings Available
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Sponsoring Units: DFD Chair: Mengying Wang, Northwestern University Room: McCormick Place W-181C |
Thursday, March 17, 2022 8:00AM - 8:12AM |
S12.00001: Rotations of Large Non-spherical Particles in Turbulence Greg A Voth Many different approaches are used to define scale-local structures which can be used to quantify the multi-scale dynamics of the turbulent cascade. One very concrete option is to use the rotational motion of rigid bodies. For example, the tumbling rate of slender fibers has been shown to display inertial range scaling with the mean square tumbling rate scaling as d-4/3 where d is the fiber length. A measured particle history provides a sampling of the dynamic evolution of the flow structure at the scale of the particle. Particle shape plays a central role due to preferential alignment of non-spherical particles by the strain produced by the flow structure. This talk will discuss what we have learned from measuring rotations of large particles in turbulence and the picture that is emerging from recent numerical and experimental work. |
Thursday, March 17, 2022 8:12AM - 8:24AM |
S12.00002: Wall modeled LES for variable viscosity turbulence Kazuhiko Suga, Haruki Sugimoto, Yusuke Kuwata Modification of turbulence by temperature-dependent fluid properties is not ignorable when a relatively large temperature difference is imposed on the flow fields. It is true particularly for high Prandtl number flows heated/cooled from the wall boundaries. Since most of the algebraic wall models simply assume constant fluid properties, it is required to provide an alternative model to simulate such a flow field. Indeed, models based on the equilibrium logarithmic law cannot describe the effects of variable viscosity. This study hence proposes a wall-modelled LES method by introducing a temperature-dependent near-wall layer for the viscosity. With a simple model function for the viscosity, the steep near-wall variation of the temperature-dependent viscosity is described. We then integrate the Favre averaged thin boundary layer equations for the momentum and the temperature to construct an algebraic non-equilibrium wall model. The present LES shows that the proposed model successfully reproduces the skewed mean velocity and temperature profiles owing to the temperature-dependent variable viscosity. |
Thursday, March 17, 2022 8:24AM - 8:36AM |
S12.00003: The inverse problem in fingered growth – inferring growth rules from the final pattern. Piotr Szymczak, Stanisław Zukowski, Hansjörg Seybold Many physical processes involving moving boundaries produce fingering patterns. Well-known examples include viscous fingering, electrochemical deposition or crystallization in supercooled liquids. They all involve a field (pressure, concentration or temperature depending on a problem) which is driving the growth, with the growth velocity dependent on the field gradient. The growing interface is often unstable to perturbations that evolve into fingers. The fingers split as they grow, with the daughter branches competing with each other for the available flux. This results in a formation of a ramified, network-like pattern. |
Thursday, March 17, 2022 8:36AM - 8:48AM |
S12.00004: Momentum gap states in transverse spectra in liquids Jaeyun Moon, Takeshi Egami Transverse excitations in liquids have been a focus of intense research interests in recent years as they are closely related to macroscopic properties including heat capacity, thermal conductivity, and viscosity. Prior works have shown that rather than the transverse dispersion extending to k = 0, there exists a wavevector gap (kgap) in liquids, now well-described by generalized hydrodynamics. However, finite widths at zero frequency in the momentum gap are still observed and the nature of these momentum gap states remains unexplored. In this work, we perform molecular dynamics on prototypical metallic liquids, Cu56Zr44 and Fe over a wide range of temperatures and find intimate relations between the widths of the momentum gap states and the diffusion coefficients over all temperatures studied. Our results, therefore, open novel prospects for understanding microscopic picture of transverse excitations in liquids. |
Thursday, March 17, 2022 8:48AM - 9:00AM |
S12.00005: Charge and mass transfer by inelastic collisions S. Ravichandran, John S Wettlaufer Charge-separation in cirrus clouds, a precursor for lightning in the atmosphere, occurs through the inelastic collisions and consequent transfer of mass between ice particles of different sizes. The amount of mass, and thus charge, transferred directly depends on the kinetic energy lost during the collision. We study, using particle-resolving direct numerical simulation (DNS) in two dimensions, the collisions of circular bodies settling under gravity in externally imposed flows. We vary the nondimensional Reynolds number Re = U a1 / ν, where U is the settling velocity scale, a1 is the radius of the larger particle and ν is the fluid viscosity; the ratio of particle sizes a2 / a1 ; and the scale of the background shear velocity Uf. In the absence of externally imposed shear, we find that wake capture is effective for small Re and leads to collision, but that the relative velocities at collision are small, while larger Re leads to glancing approach between particles of different sizes. Externally imposed shear enables particle collisions at significantly higher relative velocities, and thus to larger mass and charge transfer. We will quantify the dependence of the magnitude of charge transfer on the strength of externally imposed flow. |
Thursday, March 17, 2022 9:00AM - 9:12AM |
S12.00006: Nucleus-acoustic solitary waves in thermally degenerate magnetized quantum plasma Jhorna Akter, A A Mamun A thermally degenerate magneto-rotating quantum (TDMRQ) plasma having ultra-relativistic or non-relativistic thermally degenerate inertialess electrons, non-relativistic thermally degenerate inertial light nucleus and stationary heavy nucleus has been considered. A Korteweg de Vries equation has been derived by using reductive perturbation method to analyze the basic features (i.e., height and width) of degenerate pressure driven nucleus-acoustic solitary waves (DPDNASWs) in a TDMRQ plasma. It has been observed that the temperature of electron and magnetic field modify the amplitude and width of the DPDNASWs. The thermally degenerate plasma model under consideration is applicable not only to all cold white dwarfs, but also to many hot white dwarfs, such as DQ white dwarfs, white dwarf H1504+65, white dwarf PG 0948+534, etc. |
Thursday, March 17, 2022 9:12AM - 9:24AM |
S12.00007: An asymptotic interpretation for the maximum growth rate of the Miles instability of wind waves Anthony F Bonfils, Dhrubaditya MITRA, Woosok Moon, John S Wettlaufer In 1925, Jeffreys suggested that wind waves grow because the aerodynamic pressure is in phase with the wave slope; this is known as the sheltering hypothesis. Considering an inviscid parallel flow, $U(z)$, of air over water, Miles uncovered in 1957 an instability of the wind field in presence of surface waves. The origin of this instability was identified by Lighthill in 1962: there is a critical level $z_c$, at which the wind speed matches the phase speed of the surface waves and where the wind transfers energy to the waves. The point $z_c$ is a regular singularity of the Rayleigh equation, which describes the stability of the wind field. Here, we find asymptotic solutions of the Rayleigh equation for long waves, that is for waves whose wavelength is much larger than the length scale of the wind profile. We use those solutions to calculate analytically the growth rate of the Miles instability. In the strong wind limit, we show that the maximum growth rate occurs when the Jeffreys sheltering hypothesis holds. |
Thursday, March 17, 2022 9:24AM - 9:36AM |
S12.00008: A Review of Four Centuries of History of the Properties of Water, from Newton's Mechanics and Infinitesimal Calculus to the Hexagonal Close Packed Periodic Lattice and its Extension to Condensed and Dilute Matters in our Universe and The Universe. Chihtang Sah, Bin B Jie, Cindy Tianhui Jie This talk traces the history of science-based physics-understanding and mathematics-engineering of Earth most abundant, Water Matter and Materials, during the past four centuries, beginning with the continuum or “analog” Newton’s Mechanics and his Infinitesimal Calculus, to our newly discovered “digital” periodic Lattice Model of the three material phases of Water, Solid (ice), Liquid (fluid) and Gas (vapor), which we have characterized by the eigenvalues-normal modes of its 36x36 dynamical matrix. After a review of the new features of our model which were obtained from top-down explanation of several daily observed water properties, we present our water model’s possible extensions to model the other condensed matters and materials, including nuclear, particle and cosmology physics, and our mortal Universe and Einstein’s immortal Universe. We show illustrations from Solid Geometry paper models and Differential Algebraic numerical computations, their computer plotted graphs on 2D flat paper in order for the human eyes to see, its 3-D geometry, and Python blendered particle tracks as well as pathways at thermodynamic equilibrium and arbitrary deviation from equilibrium driven by an applied force, in all three directions, of the ”Make Sense” and “Meet Sensibility” human landscape. |
Thursday, March 17, 2022 9:36AM - 9:48AM |
S12.00009: Creation of an isolated turbulent blob sustained by vortex ring injection Takumi Matsuzawa, Noah P Mitchell, Stephane Perrard, William T. M. Irvine We experimentally study a steady, localized blob of turbulence, sustained by the collision of multiple vortex rings. Through PIV and 3D PTV, our measurements reveal that the blob consists of a turbulent core surrounded by comparatively quiescent fluid. We examine the transport of mass, energy, and enstrophy to elucidate the formation of the confined turbulence. The turbulent intensity and geometry of the blob could be fully tuned by altering the properties of the injected vortex rings. Our work paves the way to sculpt turbulence at a target location with a controlled injection of energy, enstrophy, and helicity. |
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