Abstract
Velocity measurements have been done in order to clarify the flow reattachment locations over a 3D backward-facing step in a duct by PIV for low Reynolds numbers 400. The aspect ratio and the expansion ratio of the stepped duct were 16 and 2, respectively. It was found that the reattachment location changes periodically at the center of a duct, and this periodicity becomes weak as it goes from the center to the side wall. At the center of a duct, since both of the clockwise and the counterclockwise vortex generate equally and move toward downstream, the reattachment location appears between them. On the other hand, at the location having a little bit distance from the center of the duct, counterclockwise vortex becomes large compared to that of the center of the duct.
