The falling motions of loaded cylinders and discs simulating snow crystals

Abstract

AbstractThe clustering, by wake capture, of thin cylinders and discs as they fall through a viscous liquid has been studied, and the relevance of the observations to the aggregation of snow crystals is discussed. The influence of captured cloud droplets on the orientation and falling motion of columnar and plate‐like snow crystals is inferred from the behaviour, in a viscous liquid, of solid cylinders and discs loaded with small spheres and from the motion in air of loaded discs of thin tissue paper. The orientation in the atmosphere of composite ice crystals in the form of columns with end plates may be inferred from the behaviour of cylinders capped by thin discs in a viscous liquid. These observations on the falling speed, orientation and aerodynamic stability of snow crystals are pertinent to their aggregation into snowflakes, their accretion of cloud droplets and dust particles, and to the optical effects they produce in the atmosphere.