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Article

A Wind Tunnel Investigation into the Aerodynamics of Lobed Hailstones

1
Institute for Atmospheric Physics, Johannes Gutenberg University, 55122 Mainz, Germany
2
Max Planck Institute for Chemistry, 55128 Mainz, Germany
3
National Center for Atmospheric Research, Boulder, CO 80305, USA
*
Author to whom correspondence should be addressed.
Atmosphere 2020, 11(5), 494; https://doi.org/10.3390/atmos11050494
Received: 17 April 2020 / Revised: 5 May 2020 / Accepted: 7 May 2020 / Published: 12 May 2020
(This article belongs to the Special Issue Microphysics of Precipitation Particles: Raindrops, Hail, and Snow)
The complex surface geometries of hailstones affect their fall behavior, fall speeds, and growth. Systematic experimental investigations on the influence of the number and length of lobes on the fall velocity and the drag coefficient of hailstones were performed in the Mainz vertical wind tunnel to provide relationships for use in numerical models. For this purpose, 3D prints of four artificial lobed hailstone models as well as spheres were used. The derived drag coefficients show no dependency in the Reynolds number in the range between 25,000 and 85,000. Further, the drag coefficients were found to increase with increasing length of lobes. All lobed hailstones show higher or similar drag coefficients than spheres. The terminal velocities of the the hailstones with short lobes are very close to each other and only reduced by about 6% from those of a sphere. The terminal velocities from the long lobed hailstones deviate up to 21% from a sphere. The results indicate that lobes on the surface of hailstones reduce their kinetic energy by a factor of up to 3 compared to a sphere. This has important consequences for the estimation of the destructive potential of hailstones. View Full-Text
Keywords: lobed hailstones; wind tunnel experiments; precipitation; drag coefficient; surface roughness lobed hailstones; wind tunnel experiments; precipitation; drag coefficient; surface roughness
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MDPI and ACS Style

Theis, A.; Borrmann, S.; Mitra, S.K.; Heymsfield, A.J.; Szakáll, M. A Wind Tunnel Investigation into the Aerodynamics of Lobed Hailstones. Atmosphere 2020, 11, 494. https://doi.org/10.3390/atmos11050494

AMA Style

Theis A, Borrmann S, Mitra SK, Heymsfield AJ, Szakáll M. A Wind Tunnel Investigation into the Aerodynamics of Lobed Hailstones. Atmosphere. 2020; 11(5):494. https://doi.org/10.3390/atmos11050494

Chicago/Turabian Style

Theis, Alexander, Stephan Borrmann, Subir K. Mitra, Andrew J. Heymsfield, and Miklós Szakáll. 2020. "A Wind Tunnel Investigation into the Aerodynamics of Lobed Hailstones" Atmosphere 11, no. 5: 494. https://doi.org/10.3390/atmos11050494

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