Ultrasound scattering by forced laminar wakes

Rodrigo H. Hernández Pellicer (1) , Christophe Baudet (2)

1 USACH - Universidad de Santiago de Chile [Santiago]
2 LEGI - Laboratoire des Écoulements Géophysiques et Industriels [Grenoble]

Most of flows found in nature belong to the class of spatially developing open flows. In this hydrodynamic class,fluid particles enter and leave the flow boundaries of the observation domain continuously. It is the case of boundary layers [1],jets [3,4] and notably wakes [5]. Actually, concepts of absolute and convective instability have proved to be useful to classify the different types of open flows according to their local dynamic behavior. A flow system like the wake,created by the presence of a thin flat plate,fall into the class of noise amplifiers [6,7]. The system become very sensitive to external noise which it is therefore amplified. It is well known that every portion of the wake is convective (stable or unstable); the system presents an extrinsic dynamics,what means that the spatial evolution of the flow is essentially determined,either by the external noise entering the system or by a coherent particular applied forcing. A wake can also display an intrinsic dynamics either by some adequate hydrodynamic resonance or by the onset of localized regions of absolute instability. Vortical structures that are formed become however very insensitive to the incoming external noise and display a very definite oscillation frequency [9]

Domaines: Mécanique des fluides [physics.class-ph]; Mécanique des fluides [physics.class-ph]

Rodrigo H. Hernández Pellicer, Christophe Baudet. Ultrasound scattering by forced laminar wakes. Vortex Structure and Dynamics, pp.173-189, 2001, 978-3-540-44535-7. ⟨10.1007/3-540-44535-8_10⟩. ⟨hal-00183323⟩