Experimental study on the wake of porous plates

This study focus on the wake of rectangular plates with different porosities in the moderate range of Reynolds number. It is well known from the literature that the typical Von Karman vortex street can be altered by interfering with the near wake of a bluff body. Past studies with porous plates have shown that the extra injection of fluid can delay the onset or even suppress the vortex shedding and the suppression is accompanied by a fall in drag. This series of experiments attempt to advance on remaining open questions on the topic. For example, how does the wake dynamics change as the porosity increases; can vortex shedding occur even in the absence of a recirculating bubble; how does the mean structure and geometry of the wake change with porosity; do the wakes display any other type of instability. The present work shows preliminary results on a series of experiments with several plates at Reynolds number between 15,000 and 35,000. All the perforated plates have a fixed width D, and their porosities vary according to the size of the holes, from the solid plate to 30% of open area exposed to the flow. High resolution planar PIV measurements were acquired covering a large field of view of approximately 6Dx20D.