Bulletin of the American Physical Society
77th Annual Meeting of the Division of Fluid Dynamics
Sunday–Tuesday, November 24–26, 2024; Salt Lake City, Utah
Session R11: Nonlinear Dynamics: Turbulence/Chaos |
Hide Abstracts |
Chair: Alexander Yakhot Room: 155 A |
Monday, November 25, 2024 1:50PM - 2:03PM |
R11.00001: Exploring Kirchhoff dynamics with a neutrally buoyant Aref-Jones ellipsoid Oghenetega W Oguns, James Hanna The classical problem of a rigid body in an ideal fluid is a six-dimensional dynamical system with three conserved quantities. Despite its long history, and its importance as a reduced model of many fluid-structure problems, basic questions remain, including the shapes and connectivities of the three-dimensional submanifolds of solutions, and the nature of chaotic motions on these. We explore the problem with a particular ellipsoidal body, beginning with integrable motions--- steady linear translation and rotation and periodic planar tumbling and fluttering. The stability of these states depends on the relative magnitude of linear and angular momentum or energy. Linear stability, including Floquet, analysis of lower-dimensional perturbed systems is consistent with direct integration of the full system. We document instabilities leading to a variety of regular and chaotic motions, including flipping and twirling, whose trajectories appear to follow paths near saddle connections between the integrable states. Such indirect observation of these connections provides insight into the structure underlying the rich dynamics of this simple system. |
Monday, November 25, 2024 2:03PM - 2:16PM |
R11.00002: Exploring the role of long-range coupling on chaotic fluid flows using Lyapunov vectors Aditya Raj, Mark R Paul We study how weak long-range spatial coupling affects the chaotic dynamics of fluid flows. We use the Generalized Swift-Hohenberg (GSH) equation to quantify the role of a weak mean flow, or wind, on high-dimensional chaotic dynamics. The GSH equation is a canonical pattern forming system that has provided important insights into the spiral defect chaos state of Rayleigh-B\'{e}nard convection. It has been shown that spiral defect chaos requires a mean flow, yet the physical mechanisms behind this interesting result are not completely understood. A central feature of the GSH equation is a mean flow whose magnitude can be continuously varied. We investigate how the mean flow magnitude affects the chaotic dynamics by computing Lyapunov vectors and Lyapunov exponents which describe the growth or decay of small perturbations to the dynamics. Our study is motivated, in part, by our recent findings of the significant influence of spatial coupling on the chaotic dynamics of lattices of coupled maps. We are interested in building upon our physical understanding of the dynamical influence of the mean flow using the Lyapunov based diagnostics over a broad range of mean flow magnitudes. |
Monday, November 25, 2024 2:16PM - 2:29PM |
R11.00003: Ruelle--Takens--Newhouse and degenerate period-doubling routes to chaos in a wavy-channel flow under mixed convection Mohammad Hossein Doranehgard, Iman Borazjani, Nader Karimi, Larry K.B. Li We numerically investigate the effects of mixed convection on the nonlinear dynamics and heat transfer of the flow through a two-dimensional wavy channel with varying degrees of symmetry at Reynolds numbers ranging from 100 to 2200. Our findings reveal that the introduction of mixed convection significantly alters the routes to chaos of the system compared to its isothermal counterpart. We demonstrate that (i) a symmetric channel can host both the Ruelle--Takens--Newhouse and degenerate period-doubling routes to chaos, (ii) an asymmetric channel can host only the latter route, and (iii) a semi-wavy channel can host no routes to chaos under the present conditions. Crucially, the Pomeau--Manneville intermittency route to chaos, previously observed in the isothermal system, is absent under mixed convection. Furthermore, our analysis of the heat transfer characteristics reveals quadratic and cubic relationships for the Nusselt number and the thermal performance factor, respectively, as functions of the Reynolds number. This study provides valuable insights for understanding and manipulating chaotic flow in wavy channels under mixed convection, with potential applications for enhancing the performance of thermal management devices. |
Monday, November 25, 2024 2:29PM - 2:42PM |
R11.00004: Emergence of order from chaos through a continuous phase transition. Sivakumar Sudarsanan, Amitesh Roy, Induja Pavithran, Shruti Tandon, R. I. Sujith As the Reynolds number is increased, a laminar fluid flow transitions to a turbulent flow, and the range of time and length scales associated with the flow increases. Yet, in a turbulent reactive flow system, as we increase the Reynolds number, we observe the emergence of a single dominant timescale in the acoustic pressure fluctuations, indicated by the loss of multifractality of the acoustic pressure oscillations. We perform experiments in a turbulent reactive flow system consisting of flame, acoustic, and hydrodynamic subsystems interacting in a nonlinear manner. We study the evolution of short-time correlated dynamics between the acoustic field and the flame in the spatiotemporal domain of the system. The order parameter, which is defined as the fraction of the correlated dynamics, increases gradually from zero to one. Our study reveals that the variance of the order parameter, correlation length, and correlation time diverge at a critical point between chaos and order. Our results show that the observed emergence of order from chaos is a continuous phase transition. Moreover, we provide experimental evidence that three of the critical exponents characterizing this transition fall in the universality class of directed percolation. Our paper demonstrates how a real-world complex, nonequilibrium turbulent reactive flow system exhibits universal behavior near a critical point. |
Monday, November 25, 2024 2:42PM - 2:55PM |
R11.00005: On the exponential decay of turbulence in a pipe Alex Yakhot, Basheer A Khan, Shai Arogeti The crisis (critical) Reynolds number, Re=1870, was numerically established as the minimum above which turbulence in turbulent puffs persists for a long time t > 1000 advective time units. We found that turbulent energy decays exponentially at subcritical Reynolds numbers in the range of 1740–1840. The decay rate is the same as that shown by Sreenivasan in 1979, but with the addition of a constant: κ=B(d-Re)3+C. It has been established experimentally and numerically that “long-lived" turbulent puffs at supercritical Re>1870 are not maintained indefinitely. It was claimed that puffs survive for quite a long time before abruptly relaminarizing (Avila et al., Annu. Rev. Fluid Mech. 55, 2023). We used the Openpipeflow Navier-Stokes solver (openpipeflow.org) to perform highly resolved direct numerical simulations in a periodic domain (50D) for Re=1880, 1900 and 1920. For all cases, the lifetimes were very long (6000 advective time units at Re=1920), but the decay was clearly exponential rather than abrupt. |
Monday, November 25, 2024 2:55PM - 3:08PM |
R11.00006: A Predictive Framework for Flow Reversals and Excursions in Turbulence Balachandra Suri We present a dynamical framework for intermittent reversals and excursions (R&Es) of large-scale circulations in turbulence. |
Monday, November 25, 2024 3:08PM - 3:21PM |
R11.00007: Bounds on dissipation in 3-D shear flows: reduction to lower-dimensional flows Farid Rajkotia-Zaheer, David Goluskin Bounds on mean dissipation or transport by turbulent shear flows can be derived from the Navier-Stokes equations by a mathematical approach called the background method. Bounds that are optimal within this method can be computed numerically by solving an optimization problem subject to a so-called spectral constraint, which requires a quadratic integral to be non-negative for all admissible velocity fields. For computational tractability, past authors have assumed that enforcing the spectral constraint only for streamwise-invariant velocity fields gives the same result as enforcing it for fully 3D fields. This talk presents two ways of checking this assumption without performing any 3D computations: by checking the 3D spectral constraint a posteriori, and by applying a theorem of Busse (1972) for the energy stability problem. The first approach is more broadly applicable, but the second gives results that extrapolate more naturally to large Re. This talk will show applications of both approaches, including optimal bounds on dissipation for the wall-bounded Kolmogorov flow known as Waleffe flow, and a confirmation that the the optimal bounds for planar Couette flow reported by Plasting and Kerswell (2003) are indeed valid for fully 3D flows. |
Monday, November 25, 2024 3:21PM - 3:34PM |
R11.00008: Dynamics of Unidirectional Flow and Critical Reflection Speed of Flat-Top Solitons Majed Alotaibi In this presentation, we build on our prior work in which we demonstrated the unidirectional flow of flat-top solitons interacting with two reflectionless potential wells of varying depths [1]. Governed by a nonlinear Schrödinger equation with dual nonlinearity, our current results further extend the understanding of velocity windows in shallow versus deep potential wells. Additionally, we introduce an examination of soliton behavior by calculating the critical speeds necessary for the reflection and transmission of flat-top solitons. This analysis clarifies the conditions under which specific soliton widths lose their unidirectional flow when interacting with double potential wells from different directions. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2025 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700