Flow past a circular cylinder with a permeable wake splitter plate
Abstract
Measurements in the near wake region of a circular cylinder in a uniform flow in the Reynolds number range 2.5 x 10(exp 3) is approximately less than Re is approximately less than 1.8 x 10(exp 4) with permeable splitter plates spanning the wake center plane are presented. Permeability is defined by the pressure drop across the plates, and the relationship between permeability and plate solidity is determined for a set of plates constructed from woven wire mesh permitting unambiguous characterization of the splitter plates by the solidity. The effects of different solidities on the flow in the near wake are investigated using smoke wire flow visualization, hotwire anemometry, and measurements of the mean pressure at the cylinder surface, and the results are related to cylinder flow without a splitter plate. Flow visualization results demonstrate that the introduction of low solidity splitter plates does not change the basic near wake structure, and that sufficiently high solidity uncouples the largescale wake instability from the body, with the primary vortex formation occurring downstream of the separation bubble due to instability of the wake profile. Hotwire and surface pressure measurements confirm and quantify the flow visualization results, showing that the permeable splitter plates reduce the drag and modify the primary wake frequency. When the solidity is high enough that the wake is convectively unstable, the base pressure is independent of the Reynolds number and solidity. For a wide range of solidities, the same asymptotic value of the Strouhal number is reached at high Reynolds numbers. The relationship between the Strouhal number and the base pressure is discussed.
 Publication:

California Instute of Technology Technical Report
 Pub Date:
 August 1993
 Bibcode:
 1993cit..rept.....C
 Keywords:

 Bluff Bodies;
 Boundary Layer Separation;
 Circular Cylinders;
 Cylindrical Bodies;
 Flow Visualization;
 High Reynolds Number;
 Near Wakes;
 Separated Flow;
 Uniform Flow;
 Velocity Measurement;
 Base Pressure;
 Bubbles;
 Drag Reduction;
 Mesh;
 Permeability;
 Pressure Measurement;
 Strouhal Number;
 Turbulent Flow;
 Vortices;
 Fluid Mechanics and Heat Transfer