Self-Similarity of Wind Profiles in Blowing Snow Allows Outdoor Modeling

Abstract

Drifts formed by snow fences appear to be scaled in proportion to fence height over a height range of nearly two orders of magnitude. This paper examines natural scaling in terms of commonly accepted similitude criteria. It is suggested that requirements for dynamic similarity of flow fields are satisfied over a period of time because surface roughness heightz₀varies approximately as the square of shear velocityu_⋆²for saltating flows in air. This is demonstrated by intensive measurements of wind profiles over snow and ice surfaces. Satisfaction of similitude requirements for scaling particle motion is less certain, although natural sorting may effectively scale particles over a restricted range of wind speeds. Natural scaling of drifts suggests snow erosion and deposition can be studied with reduced-scale models on smooth surfaces outdoors. The feasibility of this technique is demonstrated by results from 1 : 30 scale models of 1.8 and 3.8 m snow fences on both level lake ice and irregular terrain constructed from compacted snow.