Variation of bed microtopography with time around an isolated surface-mounted cylindrical roughness element and its influence on wind flow

• Published in: Aeolian research Vol. 50; p. 100688
• Main Authors: Kang, Liqiang, Zhang, Wen, Zou, Xueyong
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.03.2021
• Subjects: air flow; Bed microtopography; dry environmental conditions; mathematical models; microrelief; Numerical simulation; roughness; Roughness element; sand; sediment transport; shear stress; wind erosion; wind speed; Wind tunnel experiment; wind tunnels; Numerical simulation; Bed microtopography; Wind tunnel experiment; Roughness element
• ISSN: 1875-9637; 2212-1684
• DOI: 10.1016/j.aeolia.2021.100688

•Bed microtopography evolution process around an isolated cylinder was analyzed.•Effect of bed topography evolution on wind flow was simulated by CFD method.•Aspect ratio has an important effect on bed topography evolution and wind flow. Bed microtopography around roughness element in the arid environment is often altered by airflow and sediment transport. Understanding the interaction among the roughness element, microtopography and airflow is important to reveal the mechanism of wind erosion around an isolated surface-mounted roughness element. The wind tunnel experiments studied the influence of cylindrical roughness element with larger aspect ratios on bed microtopography evolution, and the influence of microtopography on the wind flow around the isolated cylinder was analyzed by numerical simulation method. A deep well or scour surrounds the cylinder and a symmetrical V-shaped deposition area appears in the lee. Both the erosion and deposition areas of the wider cylinder with aspect ratio of 2 are larger than that of the taller cylinder (aspect ratio of 8). With the increase of blowing time, both the erosion and deposition areas around the wider cylinder increase, while for the taller cylinder, the sand deposition area increases first and then decreases, and the erosion area shows an increasing trend. After the local surface microtopography is adjusted, the streamwise wind velocity in the lee of the cylinder at half of cylinder height is less than the initial wind velocity on the unadjusted flat bed, while the wind speed near the ground in the lee is accelerated obviously. Moreover, the vortex in the recirculation zone behind the cylinder moves upward, leading to the increase of surface shear stress in the lee and surface erosion enhancement.