Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session F48: Fluid Mechanics  General 
Hide Abstracts 
Sponsoring Units: DFD GSNP Chair: Michael Allshouse, Northeastern University Room: BCEC 251 
Tuesday, March 5, 2019 11:15AM  11:27AM 
F48.00001: Strain rate effects on front propagation in advection reaction diffusion systems Thomas Nevins, Douglas H Kelley The growth of a reactive scalar in a flowing fluid is known as an advectionreactiondiffusion (ARD) system. In this talk I will focus on effects of flow strain rate (deformation) within ARD systems  specifically chemical systems  through experiments measuring front propagation. Fronts in this context are the borders of reacted regions. Fronts are often modelled as moving with velocity equal to the sum of flow and chemical front speed in stagnant fluid. We find strain rate to have profound effects in multiple contexts. For example, I will present how reactive mixing in a twodimensional (2D) experimental flow does not behave like a 2D ARD system due to strain rate. We also perform experiments on reactions in the presence of straining flows to demonstrate how chemical front speed is altered, how bulk reaction is changed in turn, and how in special situations stirring can actually inhibit reaction. We identify various processes by which shear strain changes front speed, and make predictions about the size of these changes. These results may explain part of why mixing changes reactions and how flow sometimes creates reaction barriers. 
Tuesday, March 5, 2019 11:27AM  11:39AM 
F48.00002: Front induced feedback in convective flowfields Saikat Mukherjee, Mark Richard Paul We numerically study the feedback between a propagating front and the underlying flowfield for a range of different parameters. The flowfields are generated by a modified form of the Boussinesq equation, which generates counter rotating convection rolls in a long shallow layer of fluid. The strength of the convection rolls is quantified by the Rayleigh number. In many reactionadvectiondiffusion systems, a difference in buoyancy between the products and the reactants creates secondary fluid rolls which interact with the existing convection rolls and affect the velocity and geometry of the propagating front and the underlying flowfield. This roll formed due to the backaction of the front on the flowfield also affects the geometry of the front interface, noticeably making it more tilted and stretched. We quantify the strength of this backaction roll by a quantity called the solutal Rayleigh number, which is related to the ratio of the buoyancy difference between the products and the reactants to the diffusion coefficient of the products. We investigate the interaction of this front induced backaction roll and the convection rolls in two dimensional cellular flow and for three dimensional spatiotemporally chaotic flow. 
Tuesday, March 5, 2019 11:39AM  11:51AM 
F48.00003: Coherent Structure Detection using Topological Tools and a Graph Theoretic Approach Caledonia Wilson, Spencer Smith For general aperiodic fluid flows, coherent structures help organize the dynamics, much as invariant manifolds and periodic orbits do for autonomous or periodic systems. The prevalence of such flows in nature and industry has motivated many successful techniques for defining and detecting coherent structures. However, these approaches often require very fine trajectory data to reconstruct velocity fields. Instead, we use topological techniques to help detect coherent trajectory sets in relatively sparse 2D fluid advection problems. More specifically, we use a homotopybased algorithm, the ensemblebased topological entropy calculation (Etec), which evolves fluid material curves forward in time as minimal length bands stretched about the moving data points. These bands are represented as the weighted edges of a triangulation, which allows us to analyze flows using graph theoretic tools. In this way, highly connected components of appropriately constructed graphs can be used to partition the fluid particles into coherent trajectory sets. 
Tuesday, March 5, 2019 11:51AM  12:03PM 
F48.00004: The Phase Diagram of Leaking Flows Heather Kurtz, Caroline Tally, Katharine Jensen When a pipe springs a leak, the exiting fluid can either jet away cleanly, dribble down along the surface, or not flow out at all. Past investigations of this “teapot effect” have focused on jetting and dribbling liquid flows separately as functions of initial flow velocity, wetting, and viscosity, but there has been little focus on the transition between flow regimes. In this work, we characterize a liquid leaking from a small hole as the flow transitions from jetting to dribbling, and dribbling to no flow. We map the phase diagram of these leaking flow transitions as a function of hydrostatic pressure and pipe tipping angle, and investigate the contributions of fluid viscosity, hole size, and surface wetting to the boundaries on this phase diagram. 
Tuesday, March 5, 2019 12:03PM  12:15PM 
F48.00005: Ensemblebased Topological Entropy Calculation in Three Dimensions Eric Roberts, Suzanne Sindi, Spencer Smith, Kevin Mitchell Topological entropy measures the number of distinguishable orbits in a dynamical system, thereby quantifying the complexity of chaotic dynamics. Such knowledge aids greatly in a wide variety of natural and industrial fluid systems, including the rapidly developing field of microfluidics and the largescale dispersion of pollutants in the Earth's atmosphere and oceans. We introduce a computational geometry framework for estimating a three dimensional flow's topological entropy from the collective motion of an ensemble of system trajectories. This work is analogous to the entropy calculation extracted from the "braiding" of system trajectories in two dimensions and is a first step towards building a triangulationbased method for computing topological entropy from an ensemble of trajectory data in three dimensions and higher. In it, we consider a twodimensional rubber sheet stretched around a collection of points in a threedimensional flow. A 3D triangulation may be used to track pointface or edgeedge collisions and the rubber sheet may be chosen as one of the faces in the initial triangulation. As the points evolve in time, they carry the sheet along with them, stretching and folding it so that its growth reflects the flow complexity. 
Tuesday, March 5, 2019 12:15PM  12:27PM 
F48.00006: Uncertainty quantification in Lagrangian clustering analysis Guilherme Salvador Vieira, Michael Allshouse Partitioning ocean flows into regions that minimally mix with their surroundings can identify materially coherent vortices and assist in search and rescue planning by reducing the search domain. One method for such partitioning is the Lagrangian clustering analysis, which identifies sets of trajectories that move as a compact set. This method has been applied to deterministic, chaotic systems, revealing underlying transport barriers. For ocean models, however, in addition to the complex dynamics, there are several sources of uncertainty, such as model initialization and parameters, limited knowledge of oceanographic processes, and ocean boundary conditions and forcing. Therefore, the Lagrangian clustering analysis, when applied to ocean forecasts, should incorporate uncertain parameters and the resulting coherent structures should be robust to model uncertainty. Through application to a geostrophic flow, we present an investigation of the sensitivity of the spectral clustering method to uncertain parameters and an approach for applying this method to an ensemble of simulations. 
Tuesday, March 5, 2019 12:27PM  12:39PM 
F48.00007: Lubricated motion in an elastic tube Marie Tani, Thomas Cambau, Jose Bico, Etienne Reyssat The motion of objects through elastic constrictions is relevant to various problems in physiology and biology. We describe a model experiment where a rigid sphere is displaced through a narrower elastic tube. Lubricating the contact with a fluid significantly reduces friction on the wall of the tube. The friction force increases as the sliding velocity to the power 1/3 and depends on the fluid viscosity, mechanical properties of the tube and geometric mismatch. We derive a scaling law and a minimal numerical model to account for our experimental data. 
Tuesday, March 5, 2019 12:39PM  12:51PM 
F48.00008: A Random Choice SPH Scheme with Adaptive Viscosity Zhixuan Cao, Abani K Patra, E. Bruce Pitman Classical smoothed particle hydrodynamics (SPH) method employs explicit artificial viscosity, which typically produce more dissipation than need, incorrectly smears contact discontinuities and overwhelms fluid turbulence. Several studies have proposed highly tuned versions of artificial viscosity, turning on and off near shocks or other troublesome wave features. A different scheme adapts Godunov\rq{}s idea of solving local Riemann problems as building blocks for SPH solver. However, these methods still introduce an effective numerical diffusion that can infect the entire numerical solution. 
Tuesday, March 5, 2019 12:51PM  1:03PM 
F48.00009: Dimensionality reduction of convectiondominated flows on an optimally morphing grid Rambod Mojgani, Maciej Balajewicz Foundations and preliminary results of a new projectionbased model order reduction approach are summarized. The method is specifically designed for convection dominated nonlinear fluid flows. In this method, the evolution of the flow is approximated on an optimally morphing grid. The lowrank grid deformation, a solution of an optimization problem, is generated in such a way that the lowdimensional representation of the states on this morphing grid has lower error when compared to traditional POD on an Eulerian grid. Global basis functions are used to approximate the state variables on the lowrank grid. It is demonstrated that in this framework, certain wavelike solutions exhibit lowrank structure and thus, can be efficiently compressed using relatively few global bases. The proposed approach is successfully demonstrated for the reduction of several representative 1D and 2D problems, featuring nonlinearities, and bidirectional waves with different boundary conditions and is compared with the traditional method on the Eulerian grid. 
Tuesday, March 5, 2019 1:03PM  1:15PM 
F48.00010: An Exact Simple Solution of the Compressible NavierStokes Equation Amador Muriel

Tuesday, March 5, 2019 1:15PM  1:27PM 
F48.00011: Bottom up lattice Boltzmann: the path from Molecular Dynamics to lattice Boltzmann methods Alexander Wagner, M. Reza Parsa, Aleksandra Pachalieva We show how lattice Boltzmann simulations can be understood as a coarsegraining and averaging of Molecular Dynamics simulations. Typically lattice Boltzmann methods are verified by analyzing the hydrodynamic limit of the method. It is known that this approach is not sufficient for several kinds of application. In contrast out approach allows to bottom up derivation of lattice Boltzmann methods, and gives guidance for the design of lattice Boltzmann (or lattice gas) methods for fluctuating and/or nonideal systems and gives an alternative path to compare competing collision operators and equilibrium distributions as well as forcing terms currently used and gives a fundamental test of what the correct form of these terms is. 
Follow Us 
Engage
Become an APS Member 
My APS
Renew Membership 
Information for 
About APSThe American Physical Society (APS) is a nonprofit membership organization working to advance the knowledge of physics. 
© 2022 American Physical Society
 All rights reserved  Terms of Use
 Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 207403844
(301) 2093200
Editorial Office
1 Research Road, Ridge, NY 119612701
(631) 5914000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 200452001
(202) 6628700