On the use of helium-filled soap bubbles for large-scale tomographic PIV in wind tunnel experiments
By Fulvio Scarano, S. Ghaemi, G. Caridi, J. Bosbach, U. Dierksheide, A. Sciacchitano. 2015
291 citations recorded by the source corpus.
Abstract The flow-tracing fidelity of sub-millimetre diameter helium-filled soap bubbles (HFSB) for low-speed aerodynamics is studied. The main interest of using HFSB in relation to micron-size droplets is the large amount of scattered light, enabling larger-scale three-dimensional experiments by tomographic PIV. The assessment of aerodynamic behaviour closely follows the method proposed in the early work of Kerho and Bragg (Exp Fluids 50:929–948, 1994) who evaluated the tracer trajectories around the stagnation region at the leading edge of an airfoil. The conclusions of the latter investigation differ from the present work, which concludes sub-millimetre HFSB do represent a valid alternative for quantitative velocimetry in wind tunnel aerodynamic experiments. The flow stagnating ahead of a circular cylinder of 25 mm diameter is considered at speeds up to 30 m/s. The tracers are injected in the free-stream and high-speed PIV, and PTV are used to obtain the velocity field distribution. A qualitative assessment based on streamlines is followed by acceleration and slip velocity measurements using PIV experiments with fog droplets as a term of reference. The tracing fidelity is controlled by the flow rates of helium, liquid soap and air in HFSB production. A characteristic time response, defined as the ratio of slip velocity and the fluid acceleration, is obtained. The feasibility of performing time-resolved tomographic PIV measurements over large volumes in aerodynamic wind tunnels is also studied. The flow past a 5-cm-diameter cylinder is measured over a volume of 20 × 20 × 12 cm3 at a rate of 2 kHz. The achieved seeding density of <0.01 ppp enables resolving the Kármán vortices, whereas turbulent sub-structures cannot be captured.
Subfields: Computational Mechanics, Environmental Engineering, Ocean Engineering
View Paper: https://www.semanticscholar.org/paper/2e9ad376017f88b178ffdd0306df662c5c7ecd7f
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In Computational Mechanics
- J. Schneiders
- Fulvio Scarano
- B. W. van Oudheusden
- Bernhard Wieneke
- A. Sciacchitano
- G. Elsinga
- Andreas Schröder
- D. Schanz
In Environmental Engineering
In Ocean Engineering
Citations in the corpus
- Dense velocity reconstruction from tomographic PTV with material derivatives (2016, background): “Finally, in the case of large-scale PIV experiments in wind-tunnels that make use of helium-filled soap bubbles (HFSB, Bosbach et al. 2009; Scarano et al. 2015), a poor concentration of tracers is reported due to the limited rate of production (Caridi et al. 2015).”