Effect of Aeolian Saltation on Air Flows Using a Sedimentological Richardson Number

In aeolian studies, researchers have made significant efforts to examine the feedback of sediment transport on turbulent air flows. This feedback effect is often attributed to the increase in apparent roughness due to aeolian saltation. However, this theory cannot explain the variability of the von Kármán constant, which is thought to be influenced by either thermal or sedimentological stratification. In this study, a first aeolian version of the integrated Richardson number was introduced to quantify saltation-induced sedimentological stratification, and a series of wind-tunnel experiments was conducted to evaluate its effects on air flow. The results indicated that, similar to thermally stable air flows, stronger sedimentological stratifications, as indicated by higher Richardson numbers, led to decreases in streamwise velocity, velocity profile slope, and the apparent von Kármán parameter. However, unlike under thermal stratification, turbulence intensity and the dimensionless Reynolds stress increased with increasing Richardson number. Compared with the sediment transport rate, the Richardson number accounts not only for sediment loading but also for sediment response effects. Therefore, it can be used to quantify the overall effect of aeolian saltation on air flows. By incorporating the air density term, it also has the potential to evaluate the combined effect of thermal stratification and aeolian saltation.