Flow Forces on a Cylinder Near a Wall or Near Another Cylinder.

摘要

Lift, drag and pressure distributions have been measured on cylinders (of various cross-section shapes) near a wall. It is found that as the cylinder approaches the wall its drag decreases and a lift (away from the wall) develops. A similar development occurs for two cylinders approaching each other (in a plane perpendicular to the flow) but in this case there is a range of gap sizes for which the flow is asymmetrical and the forces on the two cylinders are different. The asymmetry is associated with an instability in the near-wake flow, and it can be flipped (switched) by small disturbances. The results are of interest for the effects of wind on cylindrical structures parallel to the ground, for pairs of structures, like stacks, near each other, etc. (Author)