关键词: 风成沙纹, 波粒二重性, 正弦波共振

Abstract: Aeolian sand ripples are a common landform feature created by the movement of sand grains on sand bed driven by wind. The process of their formation and evolution are complex. Although there are no apparent stages in the evolutionary process, which depend essentially on the changing conditions of the wind, three rough stages are suggested by our wind funnel experiment. The first is the stage of formation, during which sand ripples are formed by sand grains creeping forward on the sand bed. Sand grain creeping requires time and involves the adjustment of position of the grains on the sand bed, i.e., sand grains are sorted out by wind. During this stage, the sand driving wind is a state of nonsaturation in which the air currents fluctuate and the grains creep. Sand ripples do not follow any typical pattern and their distribution is random. The second is the stage of development. Sand ripples develop due of the action of wave grain duality. During two stage, sand driving wind is highly satuated and a state of balance is reached between sand grain creep and the intensity of grain saltation. The wave grain duality of the sand driving wind also reaches maximum, as does the action of grain sorting by wind. Third, during the stage of disappearance, high unsaturated sand driving wind hastens the processes of the sand ripple morphological changes, disintegrate the sand ripples, and reconstitute them. Creeping is rapidly changing into soltation. These processes cause sine wave resonance between air current and sand driving wind until the sand ripples disappear. Fine sand and extremely fine sand of natural sand dunes are the grain sizes for the formation of sand ripples. The major forms of sand ripples include the wave form which is the most basic and recurrent, the abnormal forms and their derivations, all nourecurring; and the crescent form found in the border zone between the coarse and fine sand beds. The velocity of sand ripple movement is slow, raging between 10 ^-1 ～10 ¹ cm/min. The experiment formula is V_R=1.58×（V_L-5.5）^0.67(cm/min). The wave length and wave height of the sand ripples in the experiment are identical to those found in the field.

Key words: aeolian sand ripples, wave grain duality, sine wave resonance