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

Scarano, Fulvio and Ghaemi, S. and Caridi, G. and Bosbach, Johannes and Dierksheide, Uwe and Sciacchitano, Andrea (2014) On the use of helium-filled soap bubbles for large-scale Tomographic PIV wind tunnel experiments. 17th International Symposia on Applications of Laser Techniques to Fluid Mechanics Lisbon 2014, 07. - 10. July 2014, Lisbon, Portugal.

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Official URL: http://ltces.dem.ist.utl.pt/lxlaser/lxlaser2014/program.asp

Abstract

Experiments are conducted with helium-filled soap bubbles (HFSB) in the sub-millimetre diameter range in the low speed flow regime to ascertain the aerodynamic behaviour of these tracers for PIV measurements in wind tunnels. The flow-tracing fidelity of HFSB relies on their neutral buoyancy and partly on their relative size to the flow time and length scales. This study follows closely the methodology proposed in an early work by Kerho and Bragg (1994) who investigated the capabilities of HFSB within a steady potential flow close to a stagnation point. The conclusions of the present investigation differ from those drawn in the latter work as it is concluded that 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 speed varying from 5 to 30 m/s. The HFSB are injected at the end of the wind tunnel nozzle contraction. Planar high-speed PIV and PTV techniques are used to obtain the velocity field distribution, velocity streamlines and to map the fluid flow acceleration along the trajectories. PIV experiments conducted in the same conditions with micron size fog droplets are taken as a term of comparison. The parameters governing the HFSB production are also varied: helium relative to soap and relative to air flow rates. The variation of the latter parameters affects the bubble size, characterized with the shadow technique, as well as the HFSB tracing fidelity. The latter is quantified by the velocity slip and with an estimate of the time response in analogy to the case of small heavy tracers.

Item URL in elib:https://elib.dlr.de/89375/
Document Type:Conference or Workshop Item (Speech)
Additional Information:Paper-Nr.: 03.9_2_337
Title:On the use of helium-filled soap bubbles for large-scale Tomographic PIV wind tunnel experiments
Authors:
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
Scarano, FulvioDelft University of Technology, NLUNSPECIFIED
Ghaemi, S.Mechanical Engineering Department, University of Alberta, CanadaUNSPECIFIED
Caridi, G.Aerospace Engineering Department, Delft University of Technology, Delft, The NetherlandsUNSPECIFIED
Bosbach, Johannesjohannes.bosbach (at) dlr.deUNSPECIFIED
Dierksheide, UweLaVision, GöttingenUNSPECIFIED
Sciacchitano, AndreaTU-Delft (NL)UNSPECIFIED
Date:2014
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In SCOPUS:No
In ISI Web of Science:No
Page Range:pp. 1-13
Series Name:Conference proceedings online
Status:Published
Keywords:Tomographic PIV, helium-filled soap bubbles
Event Title:17th International Symposia on Applications of Laser Techniques to Fluid Mechanics Lisbon 2014
Event Location:Lisbon, Portugal
Event Type:international Conference
Event Dates:07. - 10. July 2014
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 Jul 2014 17:13
Last Modified:21 Oct 2014 13:48

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