Stereoscopic PIV measurements of flow behind an isolated low-speed axial-fan

The flow field behind a forward-swept axial-fan with five blades rotating in a water tank has been measured by a stereoscopic particle image velocimetry (SPIV) system based oil the translation configuration. In this study, a three-dimensional calibration procedure was employed to compensate the distortion and refraction of particle images. Phase-averaged velocity fields show that the flow behind an axial-fan has a periodic flow structure with respect to the blade phase and the characteristic flow structure is shifted downstream in the succeeding phase. The flow speed of fan wake has a local maximum value in the radial distance of about y/R = 0.75. Strong counter-clockwise tip vortices are shed from the utmost trailing edges of the blade, while relatively weak clockwise trailing vortices exist in the hub region. The phase-averaged velocity and turbulence intensity of the out-of-plane velocity component have large values in the region near the tip vortices and they clearly show the evolution and dissipation of tip vortices and trailing vortices moving toward the tangential direction. (C) 2003 Elsevier Inc. All rights reserved.