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Tomographic PIV measurement of coherent dissipation scale structures 10.17863/CAM.13993 Worth, Nicholas Further understanding the small scale coherent structures which occur in high Reynolds number turbulence would be of enormous benefit. Therefore, the aim of the current project was to make well resolved three-dimensional flow measurements of the mixing flow between counter rotating impellers, using Tomographic Particle Image Velocimetry (TPIV). TPIV software was developed, with a novel approach permitting a significant reduction in processing time, and a series of numerical accuracy studies contributing to the fundamental understanding of this new technique. Basic flow characterisation determined the local isotropy, homogeneity and expected Reynolds number scaling. A favourable comparison between planar PIV and TPIV increased confidence in the latter, which was used to assess the dynamics and topology of the dissipation scale structures. In support of previous investigations similar topology, strain rate alignment, scale-invariance, and clustering behaviours are demonstrated. Correlated high enstrophy and dissipation regions occur in the periphery of larger structures, resulting in intermittency. Geometry characterisation indicates a predominance of tube-like structures, which are observed to form from larger ribbon-like structures through unsteady breakdown and vortex roll-up. Significant correlation between intermittent fields of dissipation and enstrophy describe the fine scales effects. These relationships should pave the way for more accurate models, capable of relating small scales and large scales during the prediction of dynamically important quantities. University of Cambridge 2010-05-04 Thesis Doctoral Doctor of Philosophy (PhD) eng The author wishes to acknowledge funding from the Engineering and Physical Sciences Research Council through Grant No. GR/S78667/01 and a Cambridge University Doctoral Training Award. http://www.dspace.cam.ac.uk/handle/1810/237242 https://www.repository.cam.ac.uk/handle/1810/237242 https://www.repository.cam.ac.uk/bitstreams/c8da948f-7a2b-4a6a-b149-30b84ebab789/download 9b48b5ab06d23bb84928303635b366ea https://www.repository.cam.ac.uk/bitstreams/879317f6-b310-4728-826a-df042a03c9c3/download 48dcdf38f646da27e5e4bc6c1893d4fc https://www.rioxx.net/licenses/all-rights-reserved/ Tomographic particle image velocimetry Coherent structures Experimental Fluid mechanics