Determination of Ice Crystal Growth Parameters in a Supercooled Cloud Tunnel.
In order to completely understand the behavior of a dynamically changing ice crystal as it falls through a supercooled cloud, the simultaneous determination of the crystal size, mass, apparent density, and fall velocity is desirable. Based on the experience obtained in our two previous ice crystal g...
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| Format: | Text |
| Language: | English |
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1981
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| Online Access: | http://www.dtic.mil/docs/citations/ADA107263 http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA107263 |
| Summary: | In order to completely understand the behavior of a dynamically changing ice crystal as it falls through a supercooled cloud, the simultaneous determination of the crystal size, mass, apparent density, and fall velocity is desirable. Based on the experience obtained in our two previous ice crystal growth studies, a new supercooled cloud tunnel has been developed. It has successfully demonstrated the capability of accurately simulating the crystal growth under free-fall conditions in a natural supercooled cloud. The new vertically converging design for the working/observation section of the tunnel permits ice crystals to be stably suspended in a supercooled cloud airstream for indefinite lengths of time. A new fog chamber is used to make the supercooled fog homogeneous with respect to droplet number and concentration, and temperature, before entering the working/observation section. A method has been developed by which the moisture content in the supercooled fog can be controlled and held constant. The flow rate through the working/observation section is controlled by a specially designed valve which also maintains the total flow into the chamber at a constant level. This configuration keeps the supercooled fog condition constant throughout an experimental run. A special method is devised to preserve the collected ice crystals so they can be photographed from both the top and side. This method also allows for accurate crystal mass determination by melting. The flow velocity, and therefore crystal fall velocity, is continually measured by an electronic manometer while a thermocouple continually records the supercooled fog temperature. |
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