Wake‐excited raindrop oscillations
作者:
Kenneth V. Beard,
H. T. Ochs,
期刊:
AIP Conference Proceedings
(AIP Available online 1990)
卷期:
Volume 197,
issue 1
页码: 433-435
ISSN:0094-243X
年代: 1990
DOI:10.1063/1.38941
出版商: AIP
数据来源: AIP
摘要:
Interpretation of microwave scattering in rain depends on the shape of raindrops, normally considered to have an ‘‘equilibrium’’ axis ratio from a force balance at each point on the surface between surface tension, hydrostatic and aerodynamic pressure. Data from the Illinois State Water Survey raindrop cameras and also observations using a high resolution, dual‐polarization radar suggest a pronounced shift from equilibrium axis ratios for small raindrops. New laboratory measurements have been made for small water drops falling at terminal velocity. The experimental findings agree well with equilibrium axis ratios from perturbation theory ford≤1 mm, but scatter significantly above the theoretical curve ford≳1 mm. The scatter is in the same direction as the shifted axis ratios in the field observations. The one‐sided scatter is consistent with wake‐excited oscillations, but only for modes having a single nodal meridian through the poles (corresponding to spherical harmonics of degeneracy,m=1). These identified modes also best match the forcing pattern associated with eddy sheding.
点击下载:
PDF
(204KB)
返 回