Vortex Development Behind a Finite Porous Obstruction
Abstract
This experimental study describes the turbulent wake behind a two-dimensional porous obstruction, which consists of a circular array of cylinders. The cylinders extend from the channel bed through the water surface, mimicking a patch of emergent vegetation. Because of its porosity, some of the flow can pass through the patch, so that directly downstream of the patch there is a region of steady, streamwise velocity, called the steady wake. The length of the steady wake (L1) increases as the patch porosity increases, and can be predicted from the equation for the growth of a plane shear layer. The formation of a von-Karman vortex street is delayed until the end of the steady wake region. There are two regions of peak vrms behind the patch. The first peak is directly behind the patch, associated with the wake turbulence of individual cylinders. The second peak occurs further downstream, with the formation of large scale wake oscillation.
Funded by NSF-EAR.- Publication:
-
APS Division of Fluid Dynamics Meeting Abstracts
- Pub Date:
- November 2011
- Bibcode:
- 2011APS..DFDR21009N