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On the use of helium-filled soap bubbles for large-scale tomographic PIV in wind tunnel experiments

Scarano, Fulvio and Ghaemi, Sina and Caridi, Giuseppe and Bosbach, Johannes and Dierksheide, Uwe and Sciacchitano, Andrea (2015) On the use of helium-filled soap bubbles for large-scale tomographic PIV in wind tunnel experiments. Experiments in Fluids, 56 (2), pp. 1-12. Springer. DOI: 10.1007/s00348-015-1909-7 ISSN 0723-4864

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Official URL: http://download-v2.springer.com/static/pdf/284/art%253A10.1007%252Fs00348-015-1909-7.pdf?token2=exp=1432132189~acl=%2Fstatic%2Fpdf%2F284%2Fart%25253A10.1007%25252Fs00348-015-1909-7.pdf*~hmac=b03d9a757fba7799acc19a0e24a507778bfdc9193fd827a1a3eb9c50dc676af2

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 behavior closely follows the method proposed in the early work of Kerho and Bragg (1994) who evaluated the tracers 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 20x20x12 cm³ at a rate of 2 kHz. The achieved seeding density of less than 0.01 ppp enables resolving the Kármán vortices, whereas turbulent sub-structures cannot be captured.

Item URL in elib:https://elib.dlr.de/95052/
Document Type:Article
Additional Information:Published online: 11 February 2015, Article: 56:42
Title:On the use of helium-filled soap bubbles for large-scale tomographic PIV in wind tunnel experiments
Authors:
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
Scarano, FulvioTU-Delft, NLUNSPECIFIED
Ghaemi, Sina2Mechanical Engineering Department, University of Alberta, CanadaUNSPECIFIED
Caridi, GiuseppeTU-Delft, NL; g.caridi (at) tudelft.nlUNSPECIFIED
Bosbach, Johannesjohannes.bosbach (at) dlr.deUNSPECIFIED
Dierksheide, UweLaVision, GöttingenUNSPECIFIED
Sciacchitano, AndreaTU-Delft, NLUNSPECIFIED
Date:2015
Journal or Publication Title:Experiments in Fluids
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In SCOPUS:Yes
In ISI Web of Science:Yes
Volume:56
DOI :10.1007/s00348-015-1909-7
Page Range:pp. 1-12
Publisher:Springer
ISSN:0723-4864
Status:Published
Keywords:tomographic PIV, wind tunnel testing, helium filled soap bubbles, large scale PIV
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Transport
HGF - Program Themes:Terrestrial Vehicles (old)
DLR - Research area:Transport
DLR - Program:V BF - Bodengebundene Fahrzeuge
DLR - Research theme (Project):V - Next Generation Train III (old)
Location: Göttingen
Institutes and Institutions:Institute of Aerodynamics and Flow Technology > Fluid Systems
Deposited By: Micknaus, Ilka
Deposited On:21 May 2015 10:40
Last Modified:06 Sep 2019 15:25

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