About
31
Publications
1,493
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
544
Citations
Publications
Publications (31)
Using an improved numerical code we investigate the creation and evolution of quantum knots and links as defects of the Gross–Pitaevskii equation. The particular constraints put on quantum hydrodynamics make this an ideal context for application of geometric and topological methods to investigate dynamical properties. Evolutionary processes are cla...
We compute simultaneously the translational speed, the magnitude and the phase of a quantum vortex ring for a wide range of radii, within the Gross–Pitaevskii model, by imposing its self preservation in a co-moving reference frame. By providing such a solution as the initial condition for the time-dependent Gross–Pitaevskii equation, we verify a po...
Here we show how to apply a recently introduced method based on the geometric interpretation of linear momentum of vortex lines to determine dynamical properties of a network of knots and links. To show how the method works and to prove its feasibility, we consider the evolution of quantum vortices governed by the Gross-Pitaevskii equation. Accurat...
We propose a quasi-Newton minimization approach for the solution of the p(x)-Laplacian elliptic problem, x∈Ω⊂Rm. This method outperforms those existing for the p(x)-variable case, which are based on general purpose minimizers such as BFGS. Moreover, when compared to ad hoc techniques available in literature for the p-constant case, and usually refe...
Although Fourier series approximation is ubiquitous in computational physics owing to the Fast Fourier Transform (FFT) algorithm, efficient techniques for the fast evaluation of a three-dimensional truncated Fourier series at a set of \emph{arbitrary} points are quite rare, especially in MATLAB language. Here we employ the Nonequispaced Fast Fourie...
Although Fourier series approximation is ubiquitous in computational physics owing to the Fast Fourier Transform (FFT) algorithm, efficient techniques for the fast evaluation of a three-dimensional truncated Fourier series at a set of \emph{arbitrary} points are quite rare, especially in MATLAB language. Here we employ the Nonequispaced Fast Fourie...
We extensively study the numerical accuracy of the well-known time splitting Fourier spectral method for the approximation of singular solutions of the Gross-Pitaevskii equation. In particular, we explore its capability of preserving a steady-state vortex solution, whose density profile is approximated by a very accurate diagonal Pad\'e expansion o...
We extensively study the numerical accuracy of the well-known time splitting Fourier spectral method for the approximation of singular solutions of the Gross-Pitaevskii equation. In particular, we explore its capability of preserving a steady-state vortex solution, whose density profile is approximated by a very accurate diagonal Pad\'e expansion o...
Here we show that under quantum reconnection, simulated by using the three-dimensional Gross- Pitaevskii equation, self-helicity of a system of two interacting vortex rings remains conserved. By resolving the fine structure of the vortex cores, we demonstrate that total length of the vortex system reaches a maximum at the reconnection time, while b...
We present an inverse power method for the computation of the first homogeneous eigenpair of the \(p(x)\)-Laplacian problem. The operators are discretized by the finite element method. The inner minimization problems are solved by a globally convergent inexact Newton method. Numerical comparisons are made, in one- and two-dimensional domains, with...
At finite temperatures, the motion of topological defects (such as solitons or vortices) in trapped atomic Bose-Einstein condensates is affected by the presence of an inhomogeneous cloud of thermal atoms. Recent interest in quantum turbulence leads us to investigate the temperature dependence of vortex
reconnections - events which are essential ing...
We study reconnections of quantum vortices by numerically solving the
governing Gross-Pitaevskii equation. We find that the minimum distance between
vortices scales differently with time before and after the vortex reconnection.
We also compute vortex reconnections using the Biot-Savart law for vortex
filaments of infinitesimal thickness, and find...
The liquid film remaining on a wire withdrawn from a liquid bath and forced through an annular jet is experimentally investigated
on a dedicated facility. An optical laser-based technique recently introduced to study liquid-film instabilities on small-radius
cylinders allows the measurement of the mean final thickness and wave characteristics. Expe...
The liquid film remaining on a wire withdrawn from a liquid bath and forced through an annular die is experimentally investigated on a dedicated facility. An optical laser-based technique recently introduced to study liquid-film instabilities on small-radius cylinders allows the measurement of the mean final thickness and wave characteristics. Expe...
In this paper, we introduce a new class of nonlinear Schrödinger equations (NLSEs), with an electromagnetic potential , both depending on the wavefunction Ψ. The scalar potential Φ depends on |Ψ|², whereas the vector potential satisfies the equation of magnetohydrodynamics with coefficient depending on Ψ.
In Madelung variables, the velocity field c...
The study of boundary-layer transition in supersonic flows is conducted employing infrared thermography (IRT). Several models
of swept wings are tested in a blow-down facility at Mach number 2.4. The effects of wing sweep and other parameters (angle
of attack, leading-edge contour, presence/absence of surface roughness) are successfully observed. T...
We provide a set of numerical simulations for the spatial segregation limit of two diffusive Lotka-Volterra models in presence of strong competition and inhomogeneous Dirichlet boundary conditions. We consider the classical non-variational quadratic cou-pling as well as a cubic coupling which makes the problem variational. For both cases we perform...
The spin of an airplane occurs for angles of attack beyond stall, where nonlinear aerodynamics dominates and where complex and unpredictable behaviors might induce to question whether or not such a motion is chaotic. To find an answer to this issue, wind-tunnel tests are carried out on a model of a fighter attached by its center of gravity through...
Optimal disturbances for the supersonic flow past a sharp cone are computed to assess the effects due to flow divergence. This geometry is chosen because previously published studies on compressible optimal perturbations for flat plate and sphere could not isolate the influence of divergence alone, as many factors characterized the growth of distur...
We describe the first DNS-based measurement of the complete mean response of
a turbulent channel flow to small external disturbances. Space-time impulsive
perturbations are applied at one channel wall, and the linear response
describes their mean effect on the flow field as a function of spatial and
temporal separations. The turbulent response is s...
Optimal perturbations in compressible, non-parallel boundary layers are considered here. The flows past a flat plate and past a sphere are analysed. The governing equations are derived from the linearized Navier-Stokes equations by employing a scaling that relies on the presence of streamwise vortices, which are well-known for being responsible for...
The three-dimensional, algebraically growing instability of a Blasius boundary layer is studied in the nonlinear regime, employing a nonparallel model based on boundary layer scalings. Adjoint-based optimization is used to determine the “optimal” steady leading-edge excitation that provides the maximum energy growth for a given initial energy. Like...
A new non-intrusive investigation technique developed especially for the study of liquid film instabilities occurring in the wire coating process is presented. A laser-sheet-based probe assures high spatial resolution and high frequency response, along with robustness to wire movements and vibrations. Moreover, the calibration is easy and fast, sin...
In the present work we revise results of transient growth in compressible boundary layers (flat plate and sphere) to consider the complete Mack energy norm at the outlet, without the assumption that the outflow perturbation is comprised solely of streaky structures. Optimal perturbations are still in the form of counter-rotating streamwise vortices...
Optimal and robust control for the three-dimensional algebraically growing instability of a Blasius boundary layer is studied in the nonlinear regime. First, adjoint-based optimization is used to determine an optimal control in the form of a spanwise-uniform wall suction that attenuates the transient growth of a given initial disturbance, chosen to...
In the present work, transition to turbulence in crossflow-dominated, swept-wing boundary layers is experimentally investigated. The motivation for this study is to reduce drag and sonic boom in supersonic flight. Therefore, highly swept wings with subsonic leading edges are used to prevent shock waves from forming. Experiments are performed at Mac...
A new technique for the passive laminar flow control, in the supersonic regime, over highly swept wings beyond the characteristic Mach angle is here studied. A series of previous low-speed experiments at Arizona State University has demonstrated the possibility to control stationary crossflow waves by distributed roughness near the attachment line,...
The aim of the present study is to extend the linear unsteady optimal-perturbation analysis of (Luchini 2000) to the nonlinear regime. In order to account for the nonlinear interactions, a Fourier expansion is applied in the streamwise direction and in time and the solution is decomposed in Fourier modes along both z and t. The optimal unsteady spa...
The three-dimensional, algebraically growing instability of a Blasius
boundary layer is studied in the nonlinear regime. Adjoint-based
optimization is used to determine the "optimal", steady but
spanwise-sinusoidal, leading-edge excitation that provides the maximum
energy growth for a given initial energy. A similar technique is then
used to determ...
Distributed roughness located close to the leading edge of a swept wing can be used to accomplish drag reduction via passive laminar flow control (LFC). Past research at the Unsteady Wind Tunnel (UWT) of Arizona State University (ASU), has shown that laminar-to-turbulent boundary-layer transition in swept-wing flows and in low-disturbance environme...
Abstract This work has been done in the period March–November,2006 as a collabo-