Numerical simulation of snow saltation and suspension in a turbulent boundary layer

Abstract

A new numerical model was developed to describe the development of drifting snow on a flat surface. The model uses Lagrangian stochastic theory to account for turbulence effects on the suspension of snow grains, and also includes aerodynamic entrainment, the grain‐bed collision process, wind modification by the grains, and a distribution of grain sizes. The calculated wind profile, shear stress, and mass flux near the surface agreed quantitatively with previous wind tunnel experiments. Because of turbulence, snow grains can reach 10 m high, a results that agrees with recent measurements but had not previously been simulated using saltation models. We also found that the steady state fluid shear stress exceeded the threshold stress, meaning that the grains were continually entrained by the fluid. A distinct change in the mass flux profile occurred at 0.1 m high for the following reason. Below 0.1 m, the particle inertia dominated the grain motion and turbulence had only a small effect on the motion; in contrast, above 0.1 m, most particles were less than 100 μm in diameter and their motion was mainly affected by the turbulence and not inertia. That is, the particles above 0.1 m were in suspension mode.