Gradient slope, aspect slope, profiling and contourlines are important topographic parameters that can be derived from digital elevation data obtained from different sources with exploitation of different interpolatio...Gradient slope, aspect slope, profiling and contourlines are important topographic parameters that can be derived from digital elevation data obtained from different sources with exploitation of different interpolation techniques. Geostatistical interpolation methods such as ordinary kriging models constitute reliable alternatives to deterministic approaches in creation of continuous surface models from discrete elevation data. This research aimed at extraction, analysis, and evaluation of different terrain parameters elevation measurements with the use of different ordinary kriging models including the linear model, the circular model, the spherical model, the exponential models, and the Gaussian model. Different ordinary kriging models under ESRI ArcView 3.3 package along with its 3D analyst and Spatial analysis extensions have been exploited in extraction of gradient slope maps, aspect slope maps, and hillshade maps in addition to contourline maps from a sample of elevation data. Visual analysis of the gradient slope maps shows great similarities between the slope maps from the linear, circular, spherical, and exponential OK models, however, that from OK Gaussian models look very different as different sizes and arrangements of the colour patches, referring to different tones and different textures where smooth tones and smooth textures dominate the gradient slope map from the OK Gaussian model. Thus, gradient slope degradation and smoothing are considerably high in the gradient slope map from Gaussian model compared to the slope maps from the other four OK models. Also, the mean slope in the Gaussian model records the lowest value with the lowest value of the standard deviation of slopes in the same map reflecting less structured and highly smoothed gradient slope map compared to the slope maps from the other OK models. Thus, similar sizes of the colour patches and similar tones and similar texture dominate the different aspect slope maps. This is not the case in Figure 2(e) which depicts the aspect slope map展开更多
Slope variation will significantly affect the characteristics of the wind field around a hill.This paper conducts a large-eddy simulation(LES)on an ideal 3D hill to study the impact of slope on wind field properties.E...Slope variation will significantly affect the characteristics of the wind field around a hill.This paper conducts a large-eddy simulation(LES)on an ideal 3D hill to study the impact of slope on wind field properties.Eight slopes ranging from 10°to 45°at 5°intervals are considered,which covers most conventional hill slopes.The inflow turbulence for the LES is generated by adopting a modified generation method that combines the equilibrium boundary conditions with the Fluent inherent vortex method to improve the simulation accuracy.The time-averaged flow field and the instantaneous vortex structure under the eight slopes are comparatively analyzed.The accuracy of the present method is verified by comparison with experimental data.The slope can affect both the mean and fluctuating wind flow fields around the 3D hill,especially on the hilltop and the leeward side,where a critical slope of 25°can be observed.The fluctuating wind speeds at the tops of steep hills(with slope angles beyond 25°)decrease with increasing slope,while the opposite phenomenon occurs on gentle hills.With increasing slope,the energy of the high-speed descending airflow is enhanced and pushes the separated flow closer to the hill surface,resulting in increased wind speed near the wall boundary on the leeward side and inhibiting the development of turbulence.The vortex shedding trajectory in the wake region becomes wider and longer,suppressing the growth of the mean wind near the wall boundary and enhancing the turbulence intensity.展开更多
文摘Gradient slope, aspect slope, profiling and contourlines are important topographic parameters that can be derived from digital elevation data obtained from different sources with exploitation of different interpolation techniques. Geostatistical interpolation methods such as ordinary kriging models constitute reliable alternatives to deterministic approaches in creation of continuous surface models from discrete elevation data. This research aimed at extraction, analysis, and evaluation of different terrain parameters elevation measurements with the use of different ordinary kriging models including the linear model, the circular model, the spherical model, the exponential models, and the Gaussian model. Different ordinary kriging models under ESRI ArcView 3.3 package along with its 3D analyst and Spatial analysis extensions have been exploited in extraction of gradient slope maps, aspect slope maps, and hillshade maps in addition to contourline maps from a sample of elevation data. Visual analysis of the gradient slope maps shows great similarities between the slope maps from the linear, circular, spherical, and exponential OK models, however, that from OK Gaussian models look very different as different sizes and arrangements of the colour patches, referring to different tones and different textures where smooth tones and smooth textures dominate the gradient slope map from the OK Gaussian model. Thus, gradient slope degradation and smoothing are considerably high in the gradient slope map from Gaussian model compared to the slope maps from the other four OK models. Also, the mean slope in the Gaussian model records the lowest value with the lowest value of the standard deviation of slopes in the same map reflecting less structured and highly smoothed gradient slope map compared to the slope maps from the other OK models. Thus, similar sizes of the colour patches and similar tones and similar texture dominate the different aspect slope maps. This is not the case in Figure 2(e) which depicts the aspect slope map
基金supported by the National Key R&D Plan of China(No.2018YFB1501104)the National Natural Science Foundation of China(Grant No.52278511)+1 种基金the Natural Science Foundation of Hebei Province(No.E2021210053)the Young Backbone Teacher Cultivation Program of Henan University of Technology.
文摘Slope variation will significantly affect the characteristics of the wind field around a hill.This paper conducts a large-eddy simulation(LES)on an ideal 3D hill to study the impact of slope on wind field properties.Eight slopes ranging from 10°to 45°at 5°intervals are considered,which covers most conventional hill slopes.The inflow turbulence for the LES is generated by adopting a modified generation method that combines the equilibrium boundary conditions with the Fluent inherent vortex method to improve the simulation accuracy.The time-averaged flow field and the instantaneous vortex structure under the eight slopes are comparatively analyzed.The accuracy of the present method is verified by comparison with experimental data.The slope can affect both the mean and fluctuating wind flow fields around the 3D hill,especially on the hilltop and the leeward side,where a critical slope of 25°can be observed.The fluctuating wind speeds at the tops of steep hills(with slope angles beyond 25°)decrease with increasing slope,while the opposite phenomenon occurs on gentle hills.With increasing slope,the energy of the high-speed descending airflow is enhanced and pushes the separated flow closer to the hill surface,resulting in increased wind speed near the wall boundary on the leeward side and inhibiting the development of turbulence.The vortex shedding trajectory in the wake region becomes wider and longer,suppressing the growth of the mean wind near the wall boundary and enhancing the turbulence intensity.
