A simple expression for wind erosion threshold friction velocity

TLDR

Threshold friction velocity u*ₜ is the wind speed at which erosion starts and, for idealized soils, depends only on particle size. The study proposes a simple formula for u*ₜ for spherical particles on dry, bare surfaces. The formula derives from balancing aerodynamic drag and lift against cohesion and gravity, assuming cohesion scales with particle size. The resulting expression, u*ₜ = Y₁ d^(1/2) + Y₂, with empirical constants Y₁ and Y₂, is both simple and effective.

Abstract

Threshold friction velocity u *t is the friction velocity at which wind erosion is initiated. While u *t is affected by a range of surface and soil properties, it is a function of particle size only for idealized soils. In this paper we present a simple expression for u *t for spherical particles loosely spread over a dry and bare surface. In this expression we consider the balance between the driving forces (aerodynamic drag and lift) and the retarding forces (cohesion and gravity) and assume that the cohesive force is proportional to particle size. It is found that u *t can be expressed as , with Y 1 and Y 2 being empirical constants. The new expression is both simple and effective.