2.3 Ridge microtopography model and drifting sand flux structure
measurement
The ridge models are constructed by two wood boards joined together,
creating a triangular cross-section. The angle between the boards at the
peak of the ridge was 90°, and the slope angle was 45°, so the
cross-section formed an isosceles triangle. The heights (H) of the ridge
models were 5, 7.5, 10, 12.5 and 15 cm respectively, and the ridge
spacing (L) was 5H, 10H, 15H, 20H, and 25H respectively, totally 25
ridge structures. At the central axis of the wind tunnel floor, there is
a sample trough, 1 m wide, 10 m long, and 3 cm deep . We collected a
sandy soil from the Zhenglan Banner of Inner Mongolia, in northern
China. The grain-size composition of the soil was provided by (Jia et
al., 2019). In wind erosion experiments, soil samples were spread in the
whole sample trough. Soil surface was smoothed and then the ridge models
were laid on it. A sand sampler was arranged at the end of the sample
trough to collect sand at different heights. The sand sampler is a
special sand sampler for wind tunnel developed and produced by the MOE
Engineering Research Center of Desertification and Blown-sand Control of
Beijing Normal University, which is composed by a bracket and seven sand
collecting boxes, with a height of 70 cm, and the cross-sectional area
of each sand inlet is 10 cm × 10 cm. The sand flow within the height
range of 70 cm above the bed surface can be collected. The sand
collecting box is rectangular, sealed at the bottom, wedge-shaped at the
opening end, stainless steel on three sides and mesh one side, which
serves as an exhaust port to discharge the air flow in the sand
collecting box. The inlet end of the sand collection box is designed to
be wedge-shaped, which can effectively relieve the blocking airflow at
the inlet and effectively improve the sand collection efficiency
(Fig.1). After each blowing experiment, the sand collecting box was
taken out one by one, and the sand mass was measured by an electronic
balance to calculate the structure of drifting sand flux and sand
transport rate.
RESULTS AND ANALYSIS