3‐D laser images of splash‐form tektites and their use in aerodynamic numerical simulations of tektite formation |
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| Authors: | C Samson S Butler C Fry P J A McCausland R K Herd O Sharomi R J Spiteri M Ralchenko |
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| Institution: | 1. Department of Earth Sciences, Carleton University, , Ottawa, Ontario, Canada, K1S 5B6;2. Department of Geological Sciences, University of Saskatchewan, , Saskatoon, Saskatchewan, Canada, S7N 5E2;3. Department of Earth Sciences, Western University, , London, Ontario, Canada, N6A 5B7;4. Earth Sciences Sector, Natural Resources Canada, , Ottawa, Ontario, Canada, K1A 0E8;5. Department of Computer Science, University of Saskatchewan, , Saskatoon, Saskatchewan, Canada, S7N 5C9 |
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| Abstract: | Ten splash‐form tektites from the Australasian strewn field, with masses ranging from 21.20 to 175.00 g and exhibiting a variety of shapes (teardrop, ellipsoid, dumbbell, disk), have been imaged using a high‐resolution laser digitizer. Despite challenges due to the samples’ rounded shapes and pitted surfaces, the images were combined to create 3‐D tektite models, which captured surface features with a high fidelity (≈30 voxel mm?2) and from which volume could be measured noninvasively. The laser‐derived density for the tektites averaged 2.41 ± 0.11 g cm?3. Corresponding densities obtained via the Archimedean bead method averaged 2.36 ± 0.05 g cm?3. In addition to their curational value, the 3‐D models can be used to calculate the tektites’ moments of inertia and rotation periods while in flight, as a probe of their formation environment. Typical tektite rotation periods are estimated to be on the order of 1 s. Numerical simulations of air flow around the models at Reynolds numbers ranging from 1 to 106 suggest that the relative velocity of the tektites with respect to the air must have been <10 m s?1 during viscous deformation. This low relative velocity is consistent with tektite material being carried along by expanding gases in the early time following the impact. |
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