Bulletin of the American Physical Society
74th Annual Meeting of the APS Division of Fluid Dynamics
Volume 66, Number 17
Sunday–Tuesday, November 21–23, 2021; Phoenix Convention Center, Phoenix, Arizona
Session P01: Minisymposia: Symmetry in Fluid Dynamics |
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Chair: Andrzej Herczynski, Boston College; Roberto Zenit, Brown Room: North 120 AB |
Monday, November 22, 2021 4:05PM - 4:31PM |
P01.00001: Symmetry-breaking instabilities in the bouncing droplet system Invited Speaker: John W Bush We consider the dynamics of bouncing millimetric droplets, levitating on the surface of a vibrating liquid bath. We review recent work that characterizes and rationalizes theoretically a number of symmetry-breaking instabilities that arise as the driving parameter, the vibrational acceleration, is increased progressively. Instabilities of individual droplets, droplet pairs and lattices of various geometries are considered in turn. The relation between this bouncing-droplet system and a number of microscopic systems is briefly discussed. |
Monday, November 22, 2021 4:31PM - 4:57PM |
P01.00002: Symmetry breaking due to surface tension and geometry Invited Speaker: Howard A Stone Multiphase flows occur in an enormous variety of fluid mechanics situations. The influence of surface tension at the fluid-fluid interface can be the driver for symmetry breaking, as has been demonstrated in many cases in the literature. In this talk I give recent examples of our studies of free surface flows where the concepts of symmetry, symmetry breaking, and self-similarity occur and possibly intersect. In particular, I will discuss (1) the manner in which the geometry of an ordinary pressure-driven channel flow can influence, and control, viscous fingering instabilities, (2) the case of a ``lifted” Hele-Shaw cell, where time-dependent strategies can either suppress the viscous fingering instability or maintain a series of non-splitting viscous fingers during the displacement process, and (3) a three-dimensional film drainage flow where an underlying structure of the partial differential equation for the film shape allows a transformation from three independent variables to a single variable, and the solution of the corresponding ordinary differential equation is in excellent agreement with experimental measurements. |
Monday, November 22, 2021 4:57PM - 5:23PM |
P01.00003: Time flies and memory lingers: altering the stability of synchronized states in hydrodynamically coupled oscillators. Invited Speaker: Lisa Fauci Minimal models of coupled oscillators have been used to shed light on the emergence of synchronized beating of nearby flagella or metachronal waves of arrays of cilia. Here we focus on oscillators whose motion is driven by two alternating traps, one active and one not. The activation state of the trap is governed by a geometric switch that depends upon the oscillator's distance to it. In Stokes flow, it has been shown both analytically and experimentally that two in-tandem spherical colloids, each with their its own pair of traps (all co linear), will tend towards anti-phase oscillations, with in-phase oscillations unstable. Here we show that adding some memory to the system can stabilize the in-phase oscillation. This memory may come from fluid inertia (unsteady Stokes or Navier-Stokes), weak elastic coupling of oscillators, or an altered switch that checks for a stall-velocity in addition to geometric information. This stabilization of in-phase synchrony is robust – we have considered rigid spherical oscillators in 3D Stokes and 3D unsteady Stokes, elastic filament oscillators in 3D Stokes, and flexible droplets in 2D Stokes and 2D Navier Stokes – and all demonstrate this phenomenon |
Monday, November 22, 2021 5:23PM - 5:49PM |
P01.00004: Symmetric Fluid Flows and Similarity Variables Invited Speaker: Patrick D Weidman The role of similarity variables in symmetric flows is investigated in fluid dynamics. The most important type of symmetry is the dilation symmetry which is |
Monday, November 22, 2021 5:49PM - 6:15PM |
P01.00005: Symmetry, spatio-temporal self-similarity and scaling in wall turbulence Invited Speaker: Beverley J McKeon Self-similarity of the statistics of wall turbulence has been well-studied. The properties of the mean velocity profile and a description of the inertial (logarithmic) region are well-documented, while work in the last two decades has unraveled some of the complexities of the scaling of the Reynolds stresses and spectral representations of the fluctuations. An incomplete list of recent models for the scaling behavior for these flows include the Lie group symmetry analysis of Oberlack (1999), the work of She et al. (2017), and the mean momentum balance (MMB) approach of Klewicki et al. (2007). The attached eddy hypothesis (AEH), e.g. Perry & Chong (1982), and recent extensions (Marusic & Monty, 2019) provide a static structural analog replicating much of the observed behavior. Recently explored equation- and data-driven analysis techniques such as resolvent analysis (McKeon & Sharma, 2010; Hwang & Cossu, 2010; McKeon, 2017; Jovanovic, 2021) and spectral proper orthogonal decomposition (Towne et al, 2018) permit the investigation of instantaneous coherent structure. |
Monday, November 22, 2021 6:15PM - 6:41PM |
P01.00006: Chiral symmetry avoidance through a cascade of wrinkles Invited Speaker: Emmanuel Villermaux We describe how a line initially dividing the plane spontaneously breaks its chiral symmetry by actively sustaining a cascade of successive wrinkles of ever smaller sizes. The line is an oil thread deposited at the surface of a still water bath, interacting with its environment by Marangoni stresses. |
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