X. Wang1*, G.H.P. Campmans1, T. Weinhart1, A.R. Thornton1, S. Luding1, K.M. Wijnberg1
1 University of Twente, the Netherlands
* Corresponding author: x.wang-8@utwente.nl
Introduction
Moisture plays a critical role in the dynamics of aeolian sediment transport over coastal sandy beaches. It was found from field observations that the transport over wet beach surfaces is fundamentally different from that over dry surfaces (Swann, 2021). Despite many empirical findings about the moisture effect on the threshold and transport flux, the small-scale mechanics that inter-particle moisture affects the development of transport from initiation towards equilibrium remains poorly understood (Cornelis & Gabriels, 2003).
Objective and Methods
To gain some insights into the influence of moisture on aeolian sediment transport, we introduce a discrete particle model integrated with a liquid migration model, enabling the simulation of moisture’s dynamic behavior. The model is coupled with a one-dimensional air flow model in two directions, facilitating the momentum exchange between the solid phase and the air phase. We conducted transport simulations across various wind strengths and moisture contents to systematically demonstrate the impact of moisture.
Results
Our results show that the existence of liquid bridges enhances the bed resistance against erosion, and the mechanism of introducing wet particles into saltation is by particle impact that stimulates the rupture of those liquid bridges. We further identify the liquid redistribution in the vertical direction, which is accompanied with intensive saltation. This leads to dry-particle-like transport behavior in the equilibrium state, suggesting that the moisture effect can vary with the phase of transport. The findings provide implications for bed form development at coastal sandy beaches.
Model snapshots: left) Particles connected by liquid bridges; Right) Particles transported by wind (The arrows show the velocity of particles and airflow).
References
Cornelis, W. M., & Gabriels, D. (2003). The effect of surface moisture on the entrainment of dune sand by wind: an evaluation of selected models. Sedimentology, 50(4), 771-790.
Swann, C., Lee, D., Trimble, S., & Key, C. (2021). Aeolian sand transport over a wet, sandy beach. Aeolian Research, 51, 100712.
