Experimental Investigation of the Near-Wall Turbulent Structure of Drag Reducing Channel Flow with Blowing Polymer Solution from the Wall

摘要

Turbulent drag reducing flow with blowing polymer solution from the channel wall was investigated experimentally with using Particle Image Velocimetry (PIV). Experiment was carried out with changing the condition of blowing polymer solution (e.g. weight concentration of polymer solution and blowing rate). Reynolds number based on the channel height and mean velocity was chosen 20000 and 40000. As a result, when the polymer solution is blown from the channel wall, u_(rms)~(+) is hardly affected, but v_(rms)~(+), Reynolds shear stress and correlation coefficient decrease significantly only near the blower wall. This behavior seems to correspond to decrease the ejection and sweep in the near-wall region by investigation of instantaneous velocity map and joint probability density plot.