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Le Gal P

Publications and source records attributed to Le Gal P.

7 recordsLinked to original sources
PubMed2000

Experimental study of the multipolar vortex instability

The instability of a vortex subjected to a stationary dipolar or tripolar constraint is studied experimentally by using a rotating deformable cylinder on which two or three rollers are applied. As the Reynolds number and the aspect ratio of the cylinder are varied, different modes of instability are observed and their wavelength and frequency are compared to theoretical predictions. Secondary instability and cyclic breakup are also evidenced in the elliptic geometry.

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PubMed2000

Stability analysis of plane wave solutions of the discrete ginzburg-landau equation

The discrete Ginzburg-Landau model for a family of oscillators linearly coupled with their first neighbors is studied. The full linear stability analysis of the nonlinear plane wave solutions is performed by considering both the wave number (k) of the basic states and the wave number (q) of the perturbations as free parameters. In particular, it is shown that nonlinear plane waves can be destabilized not only by long (q-->0) or short (q=pi) wave perturbations, but also by intermediate wave numbers (0<q<pi). Finite size effects are also considered and discussed in connection with experiments on coupled oscillating wakes.

Journal Article↗
PubMed2000

Visualization of the space-time impulse response of the subcritical wake of a cylinder

The well-known Benard-von Karman cylinder wake is one of the most challenging phenomena of fluid mechanics. As the Reynolds number of the flow around a cylinder passes through a critical value, alternating vortex shedding appears via a Hopf bifurcation. Theoretical studies of the wake have described the appearance of this self-sustained oscillation as the result of a convective to absolute transition resulting in the formation of a global mode. We illustrate here the convective global regime of the subcritical wake by analyzing visualizations of its impulse response.

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