Large-scale tomographic particle image velocimetry using helium-filled soap bubbles
Kühn, Matthias and Ehrenfried, Klaus and Bosbach, Johannes and Wagner, Claus (2011) Large-scale tomographic particle image velocimetry using helium-filled soap bubbles. Experiments in Fluids, Vol. 50 (4), pp. 929-948. Springer Verlag, Berlin Heidelberg. DOI: 10.1007/s00348-010-0947-4.
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To measure large-scale flow structures in air, a tomographic particle image velocimetry (tomographic PIV) system for measurement volumes of the order of one cubic metre is developed, which employs helium-filled soap bubbles (HFSBs) as tracer particles. The technique has several specific characteristics compared to most conventional tomographic PIV systems, which are usually applied to small measurement volumes. One of them is spot lights on the HFSB tracers, which slightly change their position, when the direction of observation is altered. Further issues are the large particle to voxel ratio and the short focal length of the used camera lenses, which result in a noticeable variation of the magnification factor in volume depth direction. Taking the specific characteristics of the HFSBs into account, the feasibility of our large-scale tomographic PIV system is demonstrated by showing that the calibration errors can be reduced down to 0.1 pixels as required. Further, an accurate and fast implementation of the multiplicative algebraic reconstruction technique, which calculates the weighting coefficients when needed instead of storing them, is discussed. The tomographic PIV system is applied to measure forced convection in a convection cell at a Reynolds number of 530 based on the inlet channel height and the mean inlet velocity. The size of the measurement volume and the interrogation volumes amount to 750 mm × 450 mm × 165 mm and 48 mm × 48 mm × 24 mm, respectively. Validation of the tomographic PIV technique employing HFSBs is further provided by comparing profiles of the mean velocity and of the root mean square velocity fluctuations to respective planar PIV data.
|Additional Information:||Published online: 14 August 2010|
|Title:||Large-scale tomographic particle image velocimetry using helium-filled soap bubbles|
|Journal or Publication Title:||Experiments in Fluids|
|In ISI Web of Science:||Yes|
|Page Range:||pp. 929-948|
|Publisher:||Springer Verlag, Berlin Heidelberg|
|Keywords:||Tomographic PIV, Large-scale PIV, Helium filled soap bubble, Calibration errors, MART implementation, LED light source, Validation, Confined forced convection|
|HGF - Research field:||Aeronautics, Space and Transport|
|HGF - Program:||Aeronautics|
|HGF - Program Themes:||L AR - Aircraft Research|
|DLR - Research area:||Aeronautics|
|DLR - Program:||L AR - Aircraft Research|
|DLR - Research theme (Project):||L - Flight Physics|
|Institutes and Institutions:||Institute of Aerodynamics and Flow Technology > Fluid Systems|
|Deposited By:||Matthias Kühn|
|Deposited On:||22 Sep 2010 08:48|
|Last Modified:||04 Apr 2013 16:18|
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