Abstract
Flow visualization of air flow in a sharp 180-degree turn of a square cross-section duct was conducted using paraffin-mist as a tracer.
In the previous paper, it was shown that there exist a large-scale 3-dimensional flow structure accompanied by a strong reverse flow along the surface of the outer corner, and a strong secondary flow in the entrance of the first turn.
In the present experiments, we observed the cross-sectional views perpendicular to the flow axis using a laser light sheet. It was found through the present study that at the plane of 30-45-degree of the first 90-degree turn a pair of vortex starts to appear. At the outlet region of the second 90-degree turn four vortex pairs are found to be existing.
