The study of bed-load transport is of great significance both in theory and in practice.This paper discusses the saltation of bed-load solid grains in flowing water.Experiments and theoretic analysis have been made by...The study of bed-load transport is of great significance both in theory and in practice.This paper discusses the saltation of bed-load solid grains in flowing water.Experiments and theoretic analysis have been made by means of high-speed photographing and advanced data processing technique with a combined method based on mechanical and statistical theories.It indicates that the saltation is the main form of the bed-load transport under ordinary flowing conditions.In the meantime,taking suecessive saltation as the mod- el of bed-load transport,systematic analysis has been made with regard to the kinematic properties and mechanism of saltation.The statistical analysis shows that the probability density functions of the relative height and length of saltation are in conformity with Γ-type distribution,while the probability density func- tions of the relative velocities of saltation are in conformity with the Gaussian distribution.展开更多
Due to the very fine space resolution and high noise-reduction capability of the improved laboratory-made laser Doppler anemometer, the temporal mean velocity and velocity fluctuation in uniform, rough bed open channe...Due to the very fine space resolution and high noise-reduction capability of the improved laboratory-made laser Doppler anemometer, the temporal mean velocity and velocity fluctuation in uniform, rough bed open channel turbulent flows were measured in full detail nd a large amount of information about the wall region was obtained. The influence of boundary roughness on flow characteristics was examined by changing the relative smoothness scale, H/k_s, of the flow. It is proposed that there are three sorts of bed roughness, namely, the large scale roughness, the medium one and the small one. The small scale roughness is of more universal significance to engineering practice, and much attention is devoted to the characteristics of the flow over boundaries of such a sort of roughness.展开更多
基金The project supported by National Natural Science Foundation of China
文摘The study of bed-load transport is of great significance both in theory and in practice.This paper discusses the saltation of bed-load solid grains in flowing water.Experiments and theoretic analysis have been made by means of high-speed photographing and advanced data processing technique with a combined method based on mechanical and statistical theories.It indicates that the saltation is the main form of the bed-load transport under ordinary flowing conditions.In the meantime,taking suecessive saltation as the mod- el of bed-load transport,systematic analysis has been made with regard to the kinematic properties and mechanism of saltation.The statistical analysis shows that the probability density functions of the relative height and length of saltation are in conformity with Γ-type distribution,while the probability density func- tions of the relative velocities of saltation are in conformity with the Gaussian distribution.
基金Project supported by the National Natural Science Foundation of China
文摘Due to the very fine space resolution and high noise-reduction capability of the improved laboratory-made laser Doppler anemometer, the temporal mean velocity and velocity fluctuation in uniform, rough bed open channel turbulent flows were measured in full detail nd a large amount of information about the wall region was obtained. The influence of boundary roughness on flow characteristics was examined by changing the relative smoothness scale, H/k_s, of the flow. It is proposed that there are three sorts of bed roughness, namely, the large scale roughness, the medium one and the small one. The small scale roughness is of more universal significance to engineering practice, and much attention is devoted to the characteristics of the flow over boundaries of such a sort of roughness.
