3.1 Structure of drifting sand flux with no ridges
Under the condition of no ridges, the sand transport rate within the
height of 0~70 cm above the sand bed decreases with the
increase of height and continues to increase with the increase of
friction velocity (Table 1). More than 97% of the sand transport is
concentrated in the height of 0~10 cm, and the sand
transport decreases rapidly in the 10~20 cm layer,
accounting for 1.6% of the total sand transport on average. With the
increase of height, the sand transport decreases gradually, but the
decreasing rate between layers is getting smaller and smaller, and the
sand transport in each layer above 20 cm is no more than 1%. With the
increase of friction velocity, the proportion of sand transported in the
drifting sand flux layer near the bed decreases relatively, and the
proportion of sand transported in the upper layer increases accordingly.
Based on the measurement results of sand transport, the sand transport
rate at each height level (the average values of upper and lower heights
are taken for each height level) is calculated (Fig. 2), and the
correlation between the sand transport rate and height is analyzed. The
results show that the sand transport rate decreases with the increase of
height in a power function, which can be expressed by the functionq =Ah-B , and the correlation coefficients
are all above 0.941.