A method for quantifying fluctuating pressure magnitudes on the surface of a Controlled Diffusion (CD) blade was utilized to identify characteristics of the flow structure of the boundary layer at various streamwise and spanwise locations. This research effort explored the fundamental aspects of an axial fan flow field - a supplement to and a continuation of the work performed by Douglas Neal (2010). The work is driven by the motivation to identify flow structures within the boundary layer of the CD blade and characterize similarities between the results for rotating and stationary blades. These results are expected to be valuable for those working in the areas of aeroacoustics and noise prediction. Streamwise and spanwise surface pressures were measured along the surface of a stationary and a rotating CD blade. Additional trailing edge velocity wake surveys identify boundary layer features of the rotating and stationary blades. Surface pressure statistics, spectral characteristics, and correlations distinguish elements of the boundary layer from the stationary and rotating CD blades. Further results from correlations and spectral analysis on the airfoil trailing edge region identify spatial and temporal decay rates as well as parameters useful for trailing edge aeroacoustic noise prediction. An off-design operating point was evaluated to expand the context of this experiment; significant differences were observed. The fluctuating wall pressure observations are consistent with those made of a flat plate boundary layer (Willmarth and Woolridge 1962) and of the CD geometry by Moreau and Roger (2005).
Read
