An experimental study of turbulent vortex rings using particle image velocimetry

In the present study, two-dimensional and stereoscopic Particle Image Velocimetry techniques provide spatial and temporal resolved measurements of the full field of the cross-section of turbulent vortex rings, from which a more rigorous investigation of the similarity theory is possible. Since the region over which the similarity theory appears to hold starts at about 2.5 orifice diameters downstream, this study focuses on the early development region from this point to ten diameters downstream. Finally, the ensemble-averaged turbulent ring velocity contours, vorticity contours, pressure field contours, as well as Reynolds stresses and turbulence production contours, are presented. The effects of the turbulent vortex ring position dispersion and tilting angle variation on the measurement results are also studied and quantified. An effort is also made to reconstruct a three-dimensional turbulent vortex ring velocity field by adopting Taylor’s hypothesis. Some important features are successfully captured. An azimuthal-averaging method is also developed in an attempt to estimate the turbulence quantities in cylindrical coordinates. However, because of various limitations, the three-dimensional reconstruction method is not perfect, and room for future improvement is discussed.EThOS - Electronic Theses Online ServiceGBUnited Kingdo