Turbulence‐Based Model for Subthreshold Aeolian Saltation
Santosh Rana, William Anderson, Mackenzie Day
Abstract
Abstract Sand transport initiation and cessation occurs when the surface shear velocity exceeds a fluid threshold and falls below an impact threshold, respectively. Even when average shear velocity is below fluid threshold, turbulent fluctuations can initiate saltation, leading to turbulence‐driven transport intermittency. We leveraged the dynamic properties of large‐eddy simulation to recover a shear velocity time series due to atmospheric turbulence and recover a probability density function for saltation based on the frequency of events where wind has previously exceeded fluid threshold but not yet dropped below impact threshold. By conditionally sampling, we can quantitatively predict the frequency of intermediate saltation. Results show that a compensated, subthreshold shear velocity exhibits linear dependence upon the actual shear velocity. This compensated shear velocity compares favorably against field data. Model performance under terrestrial and Mars conditions is also shown.