Wind tunnel simulation experiment of mountain dunes

Mountain dunes can be categorized as echo dunes, climbing dunes and falling dunes. Their formation, development and movement are relative to sand source, flowfield near the ground, angle of mountain slope and ground subsisted environment. Through field observation and wind tunnel simulation, this paper discusses the physical mechanisms at each stage of development of mountain dunes, and reveals the principal and subordinate actions between main and lateral flow, and important actions of retarded and accelerated flow, secondary flow and separated flow. The main conclusions are: pressure coefficient on the stoss slope increases with the increase in wind velocity u(infinity), angle of attack beta and angle of slope a, while on the lee slope its variation is just the opposite; and the maximum slope for the formation of climbing dunes or the minimum slope for the formation of echo dunes are varied and decrease with increasing beta. (C) 1999 Academic Press.