On Improvement of PIV Measurements in the High-Shear Layer of a Wall-Bounded Flow

The particles utilized in particle image velocimetry (PIV) form a biased dispersion near interfaces that, in turn, lead to biased velocity measurements. This lack of seeding in the high shear region of the flow always biases the velocity measurement high as the particles are, on average, towards the far end of an interrogation window (IW) — opposite of the wall. By observing the ensemble-averaged IW particle-dispersion centroid as the corrected measurement location against the industry standard of the geometric center of the IW, this paper puts forth a methodology to correct for the biased error in flow measurements very near the wall. A typical correction to the reported velocity measurement location within a wall layer flow was seen to be approximately 75% from the geometric center to the edge of an IW. This methodology can easily be implemented in any PIV code with the express purpose of removing a source of bias error that forms by reporting measurements at the geometric center of an IW.