Denisse Sciamarella

Institut Franco-Argentin d'Études sur le Climat et ses Impacts (IFAECI) · Centre national de la Recherche Scientifique (CNRS)

Discriminating different types of chaos is still a very challenging topic, even for dissipative three-dimensional systems for which the most advanced tool is the template. Nevertheless, getting a template is, by definition, limited to three-dimensional objects based on knot theory. To deal with higher-dimensional chaos, we recently introduced the t...

Topological analysis in phase space is a fundamental chapter of dynamical systems theory. For deterministic systems, the topological structure of a flow is an invariant that provides information on the mechanisms acting in phase space to shape the flow. A topological analysis involves finding a topological representation of the underlying structure...

Random attractors are the time-evolving pullback attractors of deterministically chaotic and stochastically perturbed dynamical systems. These attractors have a structure that changes in time and that has been characterized recently using Branched Manifold Analysis through Homologies cell complexes and their homology groups. This description has be...

The definition of climate itself cannot be given without a proper understanding of the key ideas of long-term behavior of a system, as provided by dynamical systems theory. Hence, it is not surprising that concepts and methods of this theory have percolated into the climate sciences as early as the 1960s. The major increase in public awareness of t...

The definition of climate itself cannot be given without a proper understanding of the key ideas of long-term behavior of a system, as provided by dynamical systems theory. Hence, it is not surprising that concepts and methods of this theory have percolated into the climate sciences as early as the 1960s. The major increase in public awareness of t...

Random attractors are the time-evolving pullback attractors of stochastically perturbed, deterministically chaotic dynamical systems. These attractors have a structure that changes in time, and that has been characterized recently using {\sc BraMAH} cell complexes and their homology groups. This description has been further improved for their deter...

This work considers the two-dimensional flow field of an incompressible viscous fluid in a parallel-sided channel. In our study, one of the walls is fixed whereas the other one is elastically mounted, and sustained oscillations are induced by the fluid motion. The flow that forces the wall movement is produced as a consequence that one of the ends...

The theory of homologies introduces cell complexes to provide an algebraic description of spaces up to topological equivalence. Attractors in state space can be studied using Branched Manifold Analysis through Homologies: this strategy constructs a cell complex from a cloud of points in state space and uses homology groups to characterize its topol...

Noise modifies the behavior of chaotic systems in both quantitative and qualitative ways. To study these modifications, the present work compares the topological structure of the deterministic Lorenz (1963) attractor with its stochastically perturbed version. The deterministic attractor is well known to be “strange” but it is frozen in time. When d...

This work describes the application of a technique that extracts branched manifolds from time series to study numerically generated fluid particle behaviour in the wake past a cylinder performing a rotary oscillation at low Reynolds numbers, and compares it with the results obtained for a paradigmatic analytical model of Lagrangian motion: the driv...

This work proposes a reading of Laclau’s theory on populism using concepts from topology applied to dynamical systems. The analogical correspondences are established between the elements used in the reconstruction of a topological structure from data and categories such as discourse, hegemony, demand, empty and floating signifier, antagonism, and h...

Noise modifies the behavior of chaotic systems. Algebraic topology sheds light on the most fundamental effects involved, as illustrated here by using the Lorenz (1963) model. This model's attractor is "strange" but frozen in time. When driven by multiplicative noise, the Lorenz model's random attractor (LORA) evolves in time. Here, we use Branched...

Branched Manifold Analysis through Homologies (BraMAH) is a technique that computes the state-space topology of a dynamical reconstruction from scalar data. This work introduces the application of this technique to Lagrangian time series. The approach unveils the topological structure underlying the behavior of a fluid particle. When applied to a s...

Identification of dynamical distinguished Lagrangian regions in flows using topological data analysis. This thesis introduces the use of topological time-series analysis through homologies as a diagnostic for Lagrangian dynamical diversity in fluid flows. This technique, developed in the framework provided by topology of chaos, is shown to constitu...

The dynamics of an oscillating shear layer when confined is enriched by retarded actions whose physical modeling is not trivial. We present a nonlinear delayed saturation feedback model, which allows us to correctly reproduce the complex shear layer spectra observed experimentally in open cavity flows in the incompressible limit. The model describe...

Lagrangian transport in the dynamical systems approach has so far been investigated disregarding the connection between the whole state space and the concept of observability. Key issues such as the definitions of Lagrangian and chaotic mixing are revisited under this light, establishing the importance of rewriting nonautonomous flow systems derive...

The flow through two facing, identical cavities (double-cavity) is characterized experimentally, as the inflow velocity and the distance between the cavities is varied. Standard 2D2C particle image velocimetry measurements in the spanwise mid-plane provide information on the instantaneous and mean velocity flow fields. Laser Doppler velocimetry mea...

This paper reports results obtained with two-dimensional numerical simulations of viscous incompressible flow in a symmetric channel with a sudden expansion and contraction, creating two facing cavities; a so-called double cavity. Based on time series recorded at discrete probe points inside the double cavity, different flow regimes are identified...

In this work, we study the near-field of the jet flow exiting a slot-model with aspect ratio 7.5:1. The core of the slender jet separates into two streams which subsequently merge recomposing a single core jet. Axis switching occurs downstream following self-similarity rules. In order to unveil the 3D dynamics of this pre-switching bifurcation, ste...

Postglottal flow in low-order dynamical systems modeling vocal fold motion is customarily considered one-dimensional. A relaxation distance is however mandatory before the flow effectively complies with this approximation. A continuous vocal fold model is used to show that this relaxation distance can impact voice simulation through the coupling st...

We present an alternative perspective on nonharmonic mode coexistence, commonly found in the shear layer spectrum of open-cavity flows. Modes obtained by a local linear stability analysis of perturbations to a two-dimensional, incompressible, and inviscid sheared flow over a cavity of finite length and depth were conditioned by a so-called coincide...

This work discloses similarity properties of a high-aspect-ratio pulsating jet with lateral confinement exhibiting axis switching in a region close to the jet exit. The analysis is conducted separately within the major and minor planes of the jet source. The similarity relations derived from the in-plane flow equations are combined with experimenta...

This work builds upon the efforts to characterize the three-dimensional features of the glottal jet during vocal fold vibration. The study uses a Stereoscopic Particle Image Velocimetry setup on a self-oscillating physical model of the vocal folds with a uniform vocal tract. Time averages are documented and analyzed within the framework given by ob...

An ultrahigh speed camera is used to characterize the dynamics of the cross-sectional areas defined by a self-oscillating vocal-fold latex model in correlation with the synchronically registered acoustic output. The design of the vocal-fold model has been thouroughly tested to study voice production in previous works. The aim of the setup in this s...

Starting jet airflow is investigated in a channel with a pair of consecutive slitted constrictions approximating the true and false vocal folds in the human larynx. The flow is visualized using the Schlieren optical technique and simulated by solving the Navier-Stokes equations for an incompressible two-dimensional viscous flow. Laboratory and nume...

Unsteady airflow is investigated in a channel with a geometry approximating that of the human larynx. The laryngeal flow is simulated by solving the Navier-Stokes equations for an incompressible two-dimensional viscous fluid, and visualized using the Schlieren technique in an experimental setup consisting of a rigid replica of the larynx, with and...

The sudden pressure rise produced by glottal closure in the subglottal tract during vocal fold oscillation causes a flow transient which can be computed as a water hammer effect in engineering. In this article, we present a basic water hammer analysis for the trachea and the supralaryngeal tract under conditions which are analogue to those operatin...

Flow through an in-vitro rigid model of the scaled-up laryngeal channel is measured using pressure sensors and visualized using the Schlieren technique for different geometrical configurations. Three downstream flow-conditions are considered: steady, quasi-impulsive and periodical using an electromechanical device controlling the inflow and produci...

This work builds on previous efforts to characterize the dynamic development of the airflow in the glottis from a fluid mechanical point of view. A multigrid finite-difference method with immersed boundaries is implemented to solve the Navier–Stokes equations in a channel constricted by a vibrating rigid structure with a shape conforming to the hum...

The bilateral simultaneous generation of sound in some oscine songbirds leads to complex sounds that cannot be described in terms of a superposition of the isolated sources alone. In this work, we study the appearance of complex solutions in a model for the acoustic interaction between the two sound sources in birdsong. The origin of these complex...

The solutions of time-dependent PDEs may show a bewildering variety of behaviors. The example of the Kuramoto–Sivashinsky (KS) equation illustrates how simple an equation can be with extremely complex solutions. The equations for incompressible fluids are also notorious for the extremely complex behavior of their solutions. But in the latter case,...

The acoustic properties of a recently proposed two-mass model for vocal-fold oscillations are analysed in terms of a set of acoustic parameters borrowed from phenomenological glottal-flow signal models. The analysed vocal-fold model includes a novel description of flow separation within the glottal channel at a point whose position may vary in time...

Evidence is produced for the correspondence between the oscil- lation regimes of an up-to-date two-mass model and laryngeal mechanisms. Features presented by experimental electroglot- tographic signals during transition between laryngeal mecha- nisms are shown to be reproduced by the model.

We present a study of the acoustic source parameters describing glottal flow waveforms generated by the two-mass model for vo- cal fold oscillations. Numerical measurements of the acoustic pa- rameters as a function of model parameters are presented. Con- clusions are drawn from these results, concerning the correlations between acoustic parameters...

We report the analysis of branched manifolds through homologies, in order to extend the range of applicability of the topological approach to the analysis of chaotic data. Analytic and numerical cases are discussed.

Proposed observation of coherent Bragg scattering by a lattice of vortices in uniformly rotating superfulid Helium is examined. We present the calculations of the cross section for different parameter values, as well as simulations of the detected intensity of the Bragg peaks for triangular arrays with varied degrees of distortion. Within this fram...

We report the analysis of branched manifolds through homologies, in order to extend the range of applicability of the topological approach to the analysis of human speed data. Analytic and experimental cases are discussed. [S0031-9007(99)08424-0].

2. The model The syrinx of oscine birds has two parts, each of which can be controlled, to some degree, independently by the bird. Beyond this independence, the resulting sounds when two sources are active can show evidence of coupling between them. In order to determine whether this kind of vocalization is in fact the result of the physics or the...