 |
|
|
Benoît PIER and Patrick HUERRE
LadHyX, École polytechnique - CNRS, 91128 Palaiseau Cedex, France
Journal of Fluid Mechanics 435, 145–174 (2001)
A family of slowly spatially developing wakes with variable pressure gradient is numerically demonstrated to sustain a synchronized finite-amplitude vortex street tuned at a well defined frequency. This oscillating state is shown to be described by a steep global mode exhibiting a sharp Dee--Langer type front at the streamwise station of marginal absolute instability. The front acts as a wavemaker which sends out nonlinear travelling waves in the downstream direction, the global frequency being imposed by the real absolute frequency prevailing at the front station. The nonlinear travelling waves are determined to be governed by the local nonlinear dispersion relation resulting from a temporal evolution problem on a local wake profile considered as parallel. Although the vortex street is fully nonlinear, its frequency is dictated by a purely linear marginal absolute instability criterion applied to the local linear dispersion relation.
hal-00119721
2001b_pier_jfm.pdf