PIV Measurements and Statistical Analysis of the Turbulent Swirl Flow Field

Abstract

Stereoscopic PIV measurements were made during experiments conducted in order to investigate the vortex core dynamics in a straight pipe. Instantaneous flow velocity field was obtained by the use of cross-correlation of laser exposed double frame records made on frame straddling CCD cameras. Swirl flow was induced by an axial fan, positioned at the straight pipe inlet. The purpose of the PIV measurements was to document the swirl flow field and its vortex core kinematics at different volume flow rates. Measurements were made in a pipe cross-section and a meridian section, having in mind intensities of axial and circumferential velocity components and significant gradient of the radial one. In order to achieve better results, seeding parameters and camera positions have been varied. Obtained qualitative and quantitative visualization and measurement results give closer insight into physics of complex flow processes in the swirl flow. In addition these results have been compared with theoretical-experimental and numerical results. Conducted analysis points out the compatibility of the investigated results. Correlation functions, probability distributions and statistical moments of the higher order, which are determined experimentally by the use of hot-wire anemometry, together with PIV results, point out, very specific phenomena and transport processes in the core region and turbulent shear flow in pipe swirl flow. Performed investigations make possible, not just testing, but also development of the new models for this class of very complex turbulent fluid flows.