Large-scale tomographic particle image velocimetry using helium-filled soap bubbles |
| |
Authors: | Matthias Kühn Klaus Ehrenfried Johannes Bosbach Claus Wagner |
| |
Institution: | 1.Institute of Aerodynamics and Flow Technology,German Aerospace Center (DLR),G?ttingen,Germany |
| |
Abstract: | 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. |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |
|