Print Email Facebook Twitter Tomographic particle image velocimetry and its application to turbulent boundary layers Title Tomographic particle image velocimetry and its application to turbulent boundary layers Author Elsinga, G.E. Contributor Bakker, P.G. (promotor) Scarano, F. (promotor) Faculty Aerospace Engineering Date 2008-06-03 Abstract Tomographic Particle Image Velocimetry is a new experimental method developed to study three-dimensional motion in turbulent flows. The technique is an extension of standard PIV and makes use of several simultaneous views of illuminated tracer particles and their three-dimensional reconstruction as a light intensity distribution by means of tomography. The reconstructed tomogram pair is then analyzed by means of 3D cross-correlation returning the three-component velocity vector distribution over the measurement volume. The principles and details of the tomographic algorithm are discussed and a parametric study is carried out by to identify the most important parameters governing the experimental setup and to show their effect on the reconstruction accuracy. The capability of the technique in real experimental conditions is assessed with the measurement of the turbulent flow in the near wake of a circular cylinder. Next, this new technique has been applied to study the three-dimensional coherent structures in turbulent boundary layers. Quantitative visualizations of the individual (hairpin) vortices as well as the large-scale structures in both a low speed turbulent boundary layer and a high Reynolds number supersonic boundary layer have been obtained. The high Reynolds number data also suggests a very-large-scale flow organization exists not only in streamwise direction but also in spanwise direction. These very-large scale motions appear to consist of large-scale hairpins, which display a preferential alignment in streamwise direction and in the spanwise direction along the 45 degrees diagonal with the respect to the streamwise direction. Moreover, the time evolution of the flow structures is visualized in an experiment, in which the Tomographic-PIV technique is applied to nearly time-resolved image sequences recorded at 1.5 kHz. Subject pivaerodynamicsmeasurement techniqueturbulenceturbulent boundary layercoherent structures To reference this document use: http://resolver.tudelft.nl/uuid:b5aa165b-e896-42de-b31b-80fb1e72ac24 ISBN 978-90-9023158 Part of collection Institutional Repository Document type doctoral thesis Rights (c) 2008 G.E. Elsinga Files PDF elsinga_20080603.pdf 8 MB Close viewer /islandora/object/uuid:b5aa165b-e896-42de-b31b-80fb1e72ac24/datastream/OBJ/view