Structure of ice grown from droplet accretion and solidification process
In a previous wind tunnel investigation it was observed that ice crystals grown from accreted droplets are oriented so that the angle φ{symbol}, formed by their c-axis with the growth direction, has a prevailing value. In the present work, the average value of this angle φ{symbol} is studied as a fu...
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| Autores principales: | , , |
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| Formato: | JOUR |
| Acceso en línea: | http://hdl.handle.net/20.500.12110/paper_00220248_v22_n4_p303_Levi |
| Aporte de: |
| Sumario: | In a previous wind tunnel investigation it was observed that ice crystals grown from accreted droplets are oriented so that the angle φ{symbol}, formed by their c-axis with the growth direction, has a prevailing value. In the present work, the average value of this angle φ{symbol} is studied as a function of the ambient and deposit temperatures Ta and Td for -12 ≥ Ta ≥ -27 °C and -5 ≥ Td ≥ -15 °C. It is shown that, as the temperature decreases. the angle φ{symbol} increases gradually from φ{symbol} < 10° to φ{symbol} {reversed tilde} 45°. For a supercooling ΔT = -Td ≤ 9 °C, the curve φ{symbol} = φ{symbol} (Td) coincides with Pruppacher's curve of the angle α (ΔT) formed by ice dendrites with the basal plane. ForΔT >; 9 °C, φ{symbol} = φ{symbol} (Td) differs from this curve, but it agrees with Hallett's result for ΔT = 16 °C. A previous interpretation of the accretion process is considered and the agreement with the experimental results is improved by assuming that the crystal orientation is determined by thin ice sheets formed on the substrate during initial freezing. These would develop, as dendrites, in the crystallographic direction of maximum growth rate. The increase of φ{symbol} = α up to 45° and the solidification mechanism of water at high ΔT are discussed. © 1974. |
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