The Effect of Gradient and Shape on the Formation Process of Climbing Dunes in a Wind‐Tunnel Experiment

Abstract

AbstractClimbing dunes are typical aeolian landforms. The study of their formation and development mechanisms is necessary for the prevention and control of dune migration. The gradient and shape are important geomorphic factors affecting the formation of climbing dunes, but their influencing mechanism is not clear at present. In this work, wind speed and sand deposition on a sloping surface were monitored at a constant wind speed of 8 m s−1 in wind‐tunnel experiments, under six gradients (8°, 15°, 25°, 35°, 45°, and 55°) and five shapes (planar, concave, convex, concave‐convex, and stepped). The results show that (a) The flow field structure was affected by gradient and shape of the surface. The influences of flow field expanded both horizontally and vertically as the gradient increased; while at the 25° gradient, the horizontal range of influence was similar, but the vertical influence varied with different shapes. (b) The development of the sand deposition on a sloping surface could be divided into two stages. First, sand deposition occurred rapidly and climbing height, deposition area and deposition amount increased. After the surface was filled, the deposition on the surface slowed down and stabilized. (c) When the surface shape is flat, 25°–35° is the easiest gradient to form climbing dunes. Concave and stepped surfaces were more prone to form climbing dunes than were surfaces of other shapes. Those preliminary findings may enhance our understanding the formation of climbing dunes as well as provide useful references for reducing their influences upon the arid environment.