Threshold velocity of wind erosion on the surface of comet 67P

ABSTRACT Numerous aeolian landforms related to particle–fluid interactions have been observed on some active small Solar system bodies. The threshold shear velocity for erosion is a critical parameter in the formation and evolution of such features. To derive the expression of the threshold shear velocity, the threshold state of the particle bed is simplified as a balance between the driving force exerted by the fluid and the resisting forces, including cohesion and gravity. It is determined that the interparticle cohesion strength, the particle friction angle, and the particle size are three key parameters influencing the threshold shear velocity. Numerical simulations are then conducted using a self-developed lattice Boltzmann method (LBM)–discrete element method (DEM) coupled simulation platform (dembody for particles and lbmcoupler for fluid), within which a methodology is established to identify the threshold state and compute the corresponding threshold velocity. By fitting the simulation results obtained under various conditions, the coefficients in the theoretical expression are determined, resulting in a semi-analytical formulation for the threshold velocity of comet 67P. The threshold velocity exhibits a square-root dependence (power of 0.5) on both the macroscopic cohesion of the particle bed and the particle size, and a linear dependence on the square root of the tangent of the particle friction angle. The fitted results obtained from the simulation agree well with the relationships predicted by the theoretical expression, further validating the reliability of the theoretical derivation presented in this work. Based on these findings, an expression for the threshold shear velocity on comet 67P is proposed.