Relationship Between Vortex Structure and Reynolds Shear Stress of Turbulent Drag Reducing Flow With Blowing Polymer Solution From the Wall

Relation between vortex structure and Reynolds shear stress of turbulent drag reducing channel flow with blown polymer solution was investigated by using PIV in an x-y plane. Experiment was carried out at 20000 and 40000 of Reynolds number based on the bulk mean velocity and the channel height. Blowing rate of polymer solution from the channel wall was 2.0 L/min and concentration of the polymer solution was 10, 50 and 100pmm. In the present study, calculation of the vorticity and quadrant analysis were performed to clarify the relationship between the vortex structure and Reynolds shear stress. From the result of vorticty, we found low and high speed packets which have the interaction motion fluid (Q1 and Q3). On the other hand, interaction motion increases by the polymer solution with decreasing ejection and sweep. Therefore, Reynolds shear stress decreases in order to not only decreasing ejection and sweep, but also related to increasing interaction motions. Moreover, interaction motions are amplified various intensity motion against suppression of ejection and sweep are limited to weak intensity motion. But the frequency of the interaction motions stays unchanged with drag reduction rate. The result shows characteristic structure which affects decreasing of Reynolds shear stress exists in the near-wall region.