Aeolian creeping mass of different grain sizes over sand beds of varying length

Abstract

Creep is an important mode of aeolian sand transport, but it has received little attention in previous studies due to experimental difficulties and insufficient theory. In this study, we conducted 116 groups of experiments with three repeats for each group in a wind tunnel to measure the creeping mass of four different mean grain sizes (152, 257, 321, and 382 μm) over six bed lengths (2.0, 3.5, 5.0, 6.5, 8.0, and 10.0 m) at six different friction velocities (0.23, 0.35, 0.41, 0.47, 0.55, and 0.61 m/s). We attempted to develop a comprehensive model of the aeolian creeping mass by analyzing the effect of wind velocity, the particle size, and the sand bed length based on the experimental data. The primary conclusions are as follows: (1) the complex relationship among the wind velocity, the grain size, the length of the bed, and the surface shape determines sand creep. There was no unified formula to express the effect of particle sizes and the sand bed length on aeolian creeping masses, and their effects appeared to depend on each other and wind velocity, whereas the creeping mass increases with increasing wind velocity for any particle size with any length of sand bed. (2) This paper presented a predicting model to determine the aeolian creeping mass, whose calculating results can match to experimental data with correlation coefficients (R 2 ) of 0.94 or higher. (3) The effect of grain size on creeping mass can be classified into three categories: the creeping mass increases with increasing grain size, the creeping mass initially decreases and subsequently increases with increasing grain size, and the creeping mass fluctuates with the grain size. (4) The effect of increasing bed length appears to depend on the grain size. For mean grain sizes of 152, 257, and 321 μm, creep initially increases with increasing bed length before decreasing above a certain value, while for a mean grain size of 382 μm, the creeping mass gradually increased with increasing bed length. The results help to elucidate aeolian creep and provide an intense foundation for advanced study.

Aeolian Creep Transport: Theory and Experiment

“…In previous studies, mainly bed traps were used to measure creep transport rates (Bagnold, 1941; Cheng et al, 2015), and only very limited theoretical approaches for creep have been reported up to the present (Wang & Zheng, 2004). All proposed creep transport laws are either empirical or semiempirical, and lack a solid physical basis.…”

Aeolian Ripple Migration and Associated Creep Transport Rates

“…In this paper, we defined creep to be synonymous with reptation, as the terms are often used interchangeably [2][3][4][5][6] and there is no protocol for distinguishing the grain hops of creep from the grain hops of reptation. Compared to saltation, creep still remains an understudied transport phenomenon [7][8][9][10].…”

A process‐based model for aeolian sediment transport and spatiotemporal varying sediment availability

“…In an attempt to explain the poor performance of aeolian sediment transport models in coastal environments, many authors emphasized the importance of bed surface properties. Typical bed surface properties that are found along the coast and assumed to explain at least partially the poor performance of aeolian sediment transport models are high moisture contents [e.g., Wiggs et al , ; Davidson‐Arnott et al , ; Darke and McKenna Neuman , ; McKenna Neuman and Sanderson , ; Udo et al , ; Bauer et al , ; Edwards and Namikas , ; Namikas et al , ; Scheidt et al , ], salt crusts [e.g., Nickling and Ecclestone , ], bed slopes [e.g., Iversen and Rasmussen , ], vegetation [e.g., Arens , ; Lancaster and Baas , ; Okin , ; Li et al , ; Dupont et al , ], shell pavements [e.g., van der Wal , ; McKenna Neuman et al , ], and sorted and armored beach surfaces [e.g., Gillette and Stockton , ; Gillies et al , ; Tan et al , ; Cheng et al , ]. The influence of these bed surface properties on aeolian sediment transport has been investigated and often resulted in modified values for the velocity threshold [e.g., Howard , ; Dyer , ; Belly , ; Johnson , ; Hotta et al , ; Nickling and Ecclestone , ; Arens , ; King et al , ].…”