反向沙丘近地层气流变化及其对沙丘形态的影响

反向沙丘形态-动力学过程是风沙地貌的重要研究内容.选择腾格里沙漠东南缘推平沙地发育的反向沙丘为研究对象,采用二维超声风速仪对沙丘表面5个位置0.25 m和0.5 m高度的气流进行野外观测.结果表明:(1)气流方向影响近地层气流特征.以沙丘脊线垂线为轴,0.25 m高度处沙丘脊线的垂线两侧风向变化不完全对称.当丘顶气流方...

The characteristics of inner boundary layer airflow over reversing dunes and its effect on dune morphological evolution

The morphology-dynamic processing of reversing dune is an important issue in Aeolian geomorphology,but a little research have been done for these dunes,which limits our understanding of the dunes formation and development.For this reason,a developing reversing dunes in the southeast edge of Tengger Desert was selected.Ten-dimensional ultrasonic anemometer was used and set up at top,crest leeward stoss,dune toe,and windward stoss at 0.25 m and 0.5 m height over dune surface.The results indicated that:(1)The direction of airflow affects characteristics of airflow.Wind directions were not completely symmetry on the left and right sides of an axis perpendicular to the crest at 0.25 m height.When the flow angle between airflow directions and the direction of perpendicular line to the crest are negative,the wind speed at the windward slope recovers slowly.(2)The airflow characteristics of leeward slope are controlled by the wind direction.The variation of airflow at0.25 m and 0.5 m height are similar,and deflection occurs in the middle of the leeward slope,and reversing deflection occurs within a range of 10°between the airflow direction at the top of the dune and perpendicular to the crest.However,when the wind at the top of the dune is 285°-315°,the deflection at 0.25 m is greater than that0.5 m.The wind speed of 0.25 m and 0.5 m at the leeward slope is inconsistent on both sides of the direction perpendicular line to the crest.(3)Dune surface airflow affects dune morphology.During the observation period,the crest of dune moved significantly with a movement value of 0.33 m.Sediment accumulation occurred on leeward slope with the maximum thickness of 0.44 m,and erosion occurred on windward slope with the maximum depth of 0.43 m.The results of this study are important to clarify the effect of wind in the evolution of dune morphology and provide data for numerical simulation.