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We investigated the flow dynamics of tornado-like vortices, examining the influence of swirl ratio, S, defined as the ratio of tangential to radial momentum at the vortex base, on their structural characteristics. Using a combination of particle image velocimetry (PIV) in a custom-built simulator and large-eddy simulations (LES), we analyzed vortex flows at swirl ratios of S=4.66, 1.25, and 0.33. The results demonstrate that vortex flow characteristics strongly depend on S, with improved agreement between experimental and numerical data when employing flow-based swirl ratio definitions. Vortex wandering was quantified in experiments, and corrections were applied to refine tangential and radial velocity profiles. At S=0.33 and 1.25 in experiments and S=1.25 and 4.66 in simulations, the vortex transitioned from a single-celled to a double-celled structure, with further evolution into multi-celled vortices at the highest swirl ratio, substantially modifying circulation patterns. Proper orthogonal decomposition (POD) characterized the coherent structures governing vortex dynamics and their dependence on swirl ratio, revealing distinct physical features associated with each vortex regime.
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Effects of Aspect Ratio on Laboratory Simulation of Tornado-Like Vortices
Experiments were conducted in a large-scale Ward-type tornado simulator to study tornado-like vortices. Both flow velocities and the pressures at the surface beneath the vortices were measured. An interpretation of these measurements enabled an assessment of the mean flow field as well as the mean and fluctuating characteristics of the surface pressure deficit, which is a manifestation of the flow fluctuation aloft. An emphasis was placed on the effect of the aspect ratio of the tornado simulator on the characteristics of the simulated flow and the corresponding surface pressure deficit, especially the evolution of these characteristics due to the transition of the flow from a single-celled vortex to a two-celled vortex with increasing swirl ratio.
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- Award ID(s):
- 1663363
- PAR ID:
- 10089489
- Date Published:
- Journal Name:
- Wind and Structures
- Volume:
- 27
- Issue:
- 2
- ISSN:
- 1226-6116
- Page Range / eLocation ID:
- 111-121
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.12989/was.2018.27.2.111
