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- Title
Research on Statistical Roughness Characteristics of Bed Surface.
- Authors
LIN Xing-yu; CAI Tun; YANG Ke-jun
- Abstract
Riverbed roughness is an important aspect of river dynamics research, and its quantitative measurement has always been challenging. In this experiment, regardless of the macroscopic undulation of the riverbed, we laid the initial bed surface in a straight channel with non-uniform natural sand and thickened it by gradually increasing the flow rate of water. Laser scanning technology was used to obtain high-resolution bed elevation data after each bed roughening. Statistical theory and variogram function were used to investigate the surface roughness characteristics of riverbeds with varying degrees of coarseness, and to deepen the understanding of their statistical characteristics. The study's main finding is that artificially laid non-uniform sand presents an elevation frequency distribution that approximates a normal distribution. On the contrary, the frequency distribution of the stable rough bed surface formed by the continuous cumulative erosion of different flow intensities shows a slight positive deviation trend. The study found evidence that the increase of flow intensity leads strictly to an associated elevation standard deviation increase. This finding indicates that elevation standard deviation can be used as a reliable indicator to measure the characteristics of riverbed roughness in future studies. The study revealed that the kurtosis of the bed elevation data precisely de creased monotonically with the flow intensity, and that skewness and kurtosis showed a monotonic trend, indicating that they can be used to measure bed roughness. Additionally, the study found that the flow forming the bed surface is anisotropic, and as flow intensity increases, the rough layer breaks and becomes rougher again. This leads to an increase in the base value of the two-dimensional bed elevation variogram. Therefore, the study suggests that the base value of the two-dimensional variogram could serve as another reliable index for evaluating bed surface roughness. In addition, due to the influence of water flow, although the change trend of the characteristic parameters of the average variogram along the flow direction, vertical flow direction and radial profile elevation is consistent, the average variogram base value and golden point value of the transverse section are slightly larger than those of the transverse and longitudinal sections. Conversely, in the radial section, the abutment value and nugget value are considerably smaller than the values in transverse and longitudinal sections. In conclusion, this study enhances our understanding of the characteristics of bed roughness and provides crucial insights into statistical expressions for quantifying it.
- Subjects
VARIOGRAMS; DISTRIBUTION (Probability theory); GAUSSIAN distribution; SURFACE roughness; RADIAL flow; ROUGH surfaces; RIVER channels
- Publication
China Rural Water & Hydropower, 2023, Issue 10, p1
- ISSN
1007-2284
- Publication type
Article
- DOI
10.12396/znsd.230512