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Nelson Dingle and Yean Lee

Abstract

For the relationship of terminal fallspeed to size in the raindrop-size range 0.1≤d≤5.8 mm, a two-domain regression scheme is presented. The third-degree regression divided at d= reproduces the basic data from Gunn and Kinzer within 0.70% throughout the size range. The need to return to basic physical concepts is indicated, and suggests a path to a more satisfactory understanding and a more complete analytical expression of the relationship.

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A. Nelson Dingle and Yean Lee

Abstract

The fate of airborne contaminants that enter a cloud with an overriding rain, independently generated, is considered by means of three differential equations which express the overall mass conservation of contaminant. The model incorporates the physical processes of diffusive attachment, impact collection avid accretion, and includes consideration of particle and cloud droplet size spectra. The rainout ratio and rainout efficiency are evaluated on the basis of the theoretical results, and the general expressions for different cloud conditions are proposed.

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Yean Lee and Arnold A. Barnes Jr.

Abstract

A simplified analytical model is developed to analyze the removal of A12O3 particles from the TITAN rocket exhaust cloud. The model incorporates the physical processes of deposition and impact collection and includes consideration of particle size spectra. Results of computations are in good agreement with the measurements and show that sedimentation plays the most important role in the removal of the mass of material in the elevated ground cloud within the first hour after launch. The model allows for easy estimates of airborne concentrations and sedimentation when relevant sounding, exhaust mass and estimates of initial particle size distribution data are available.

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