Abstract:

Aeolian sand ripple is a wavy microtopography caused by wind on a sandy surface. Its morphological features are mostly governed by wind speed and particle size. However， few studies have investigated the influence of sand particle size distribution. As a result， the understanding of the elements influencing the morphology of sand ripples is incomplete， and the development of numerical simulation and other research methodologies is severely constrained. This research， which is based on wind tunnel experiments， sets up nine groups to observe the morphology of sand ripples at different particle size ratios. It utilizes Matlab software to extract the characteristic parameters of the sand ripples and examines their development process and saturation morphology. It is expected to provide experimental data and a comparative reference， supplementing the previous work. The following are the primary conclusions： （1） More than 30% of relatively fine sand can effectively promote the formation of sand ripples. The presence of relative coarse sand raises the upper limit of the sand ripple wavelength and sand ripple index. （2） The intervention of sand gradation parameters affects the complexity of the development process of sand ripples， so that the time to reach the stable saturation stage does not decrease linearly with the rise of wind speed. （3） The sand ripples created by the two- and three-size mixed sands become more intricate and inhomogeneous as the wind speed increases. The particle size ratio of fine sand to coarse sand is 1∶1， which allows for faster stability and better balance. In the group of equal ratio and double particle size， the particle size ratio of fine sand to medium sand = 1∶1 promotes the formation and growth of sand ripples. The sand ripple under non-equivalent double particle size conditions reveals that the windward slope has a shorter wavelength than the leeward slope. Under high wind speeds， the non-equal ratio double particle size and equal ratio three particle size groups can develop more effectively.

Key words: aeolian sand ripple, particle size distribution, morphology, wind tunnel experiment