Abstract
Flow visualization, particle image velocimetry (PIV), and laser Doppler velocimetry (LDV) are among the most useful tools available for experimental aerodynamics studies. Implementation of these techniques, however, requires that seed material be introduced into the flow. The undesirable qualities of the seeding material often prevent the use of flow visualization and velocimetry techniques in many test environments. This is particularly true for large-scale, closed-circuit tunnels where facility operators must weigh the risks of facility contamination, sensor damage, and safety concerns that might result from the introduction of seed particles. Identification of a practical clean seeding material that minimizes or eliminates these concerns would enable flow visualization and velocimetry techniques to be deployed in these facilities. Here, we demonstrate two seeding systems that have the potential to provide such a solution. The first system is a new concept which uses liquid carbon dioxide that can be made to form discrete particles as it expands from a high-pressure tank. PIV measurements are demonstrated in several flows, including supersonic and subsonic tunnels, using these residue-free seed particles. The second system utilizes a combination of steam and liquid nitrogen to produce an aerosol or fog that serves as flow seeding. Water- or steam-based seeding has been previously demonstrated for flow visualization in subsonic tunnels; here however, we utilize this seed material for PIV and LDV measurements as well as for flow visualization in a large supersonic tunnel.
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Abbreviations
- LN2:
-
Liquid nitrogen
- CO2 :
-
Carbon dioxide
- TGF:
-
Trisonic Gasdynamics Facility
- PSP:
-
Pressure-sensitive paint
- FCAD:
-
Flow Control Augmented Diffusion
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Acknowledgments
We would like to thank Dr. Richard Roberts of AEDC for funding a portion of this work as part of a Phase I SBIR, as well as Fred Heltsley and the staff at 16T for assistance with the steam/LN2 seeder development. Further thanks for supporting this project goes to Julie Saladin, Chris McGaha, and Tom Presdorf of AFRL/RBAI. Thanks are also extended to Jay Anderson and John Hixenbaugh for AFIT wind tunnel support. The views expressed in this article are those of the authors and do not reflect the official policy or position of the United States Air Force, Department of Defense, or the US Government.
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Reeder, M.F., Crafton, J.W., Estevadeordal, J. et al. Clean seeding for flow visualization and velocimetry measurements. Exp Fluids 48, 889–900 (2010). https://doi.org/10.1007/s00348-009-0784-5
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DOI: https://doi.org/10.1007/s00348-009-0784-5