Windblown sand transport is a leading factor in the geophysical evolution of arid and semi-arid regions.The evolution speed is usually indicated by the sand transport rate that is a function of launch velocity of sand...Windblown sand transport is a leading factor in the geophysical evolution of arid and semi-arid regions.The evolution speed is usually indicated by the sand transport rate that is a function of launch velocity of sand particle,which has been investigated by the experimental measurement and numerical simulation.However,the obtained results in literatures are inconsistent.Some researchers have discovered a relation between average launch velocity and wind shear velocity,while some other researchers have suggested that average launch velocity is independent of wind shear velocity.The inconsistence of launch velocity leads to a controversy in the scaling law of the sand transport rate in the windblown case.On the contrary,in subaqueous case,the scaling law of the sand transport rate has been widely accepted as a cubic function of fluid shear velocity.In order to explain the debates surrounding the windblown case and the difference between windblown and subaquatic cases,this study reinvestigates the scaling law of the vertical launch velocity of windblown transported sand particles by using a dimensional analysis in consideration of the compatibility of the characteristic time of sand particle motion and that of air flow.Then a wind tunnel experiment is conducted to confirm the revisited scaling law,where the sand particle motion pictures are recorded by a high-speed camera and then the launch velocity is solved by the particle tracking velocimetry.By incorporating the results of dimensional analysis and wind tunnel experiment,it can be concluded that,the ratio of saltons number to reptons number determines the scaling law of sand particle launch velocity and that of sand transport rate,and using this ratio is able to explain the discrepancies among the classical models of steady sand transport.Moreover,the resulting scaling law can explain the sand sieving phenomenon:a greater fraction of large grains is observed as the distance to the wind tunnel entrance becomes larger.展开更多
Windblown sand flux and dune field evolving toward the oasis have been a common ecological and environmental threat confronted by many countries.Meanwhile,it is also a kind of complex dynamical process involving multi...Windblown sand flux and dune field evolving toward the oasis have been a common ecological and environmental threat confronted by many countries.Meanwhile,it is also a kind of complex dynamical process involving multiple temporal and spatial scales which is still out of accurate description through current field observations.Available models and reliable quantitative simulations are of significant value to predict the spreading rate of desertification and provide an optimal design for sand prevention.This paper presents a 'triple-jump' method to realize quantitative simulations to the formation and evolution of an aeolian dune field from an arbitrary initial configuration.Simulated results achieve a satisfactory agreement with observations qualitatively and quantitatively,which also reveal the characteristics and dynamical behaviors of dunes and dune field.Such a paradigm is of a good level of generality,which provides an exploratory probe into the subject of multi-scale physics.展开更多
The incipient motion of sand particle from sand bed plays a very important role in the prediction of windblown sand.In this paper,we proposed a new method for predicting the incipient motion of sand particle based on ...The incipient motion of sand particle from sand bed plays a very important role in the prediction of windblown sand.In this paper,we proposed a new method for predicting the incipient motion of sand particle based on wind speed fluctuation as follows,when the wind speed is larger than the critical wind speed,if the total impulse on sand particle is larger than the critical impulse,incipient motion of sand particle would take place,otherwise if not.Furthermore,from the analysis of entrainment in the rolling and lifting modes,we come to the following conclusion.When the average wind speed is smaller than the critical wind speed,if the average wind speed is used to judge the incipient motion of sand particle,one will underestimate the number of sand particles jumping from the bed,if the instantaneous wind speed is used to judge incipient motion of sand particle,one will overestimate the number of sand particles jumping from the bed;When the average wind speed is larger than the critical wind speed,either the average or the instantaneous wind speeds is used to judge the incipientmotion of sand particles,one will overestimate the number of sand particles jumping from the bed.展开更多
It is very necessary for investigation on mechanism of windblown sand movement to understand and find out effective measures of preventing and reducing windblown sand, This also deals with some general features and ho...It is very necessary for investigation on mechanism of windblown sand movement to understand and find out effective measures of preventing and reducing windblown sand, This also deals with some general features and hot spots in the scientific forelands. such as multi-scale problems. interactions among. multi-physical-fields, randomness and nonlinearity as well as complex systems. In recent years, a series of experiments in wind tunnels and theoretical modeling as well as computer simulation have been taken by our research group （the Laboratory of Environmental Mechanics on Windblown Sand Movement in Lanzhou University ）in a cross-disciplinary （mechanics and geography） viewpoint. Several original and essential studies were explored such as the main regularities of charges on sand particles, the mechanisms of electric field in windblown sand flux, the effects induced by the electric field on the flux, the microwave propagations, the evolution process of windblown and flux under mutual couple interations among several physical fields, and the simulation of the main features of Aeolian sand ripples.展开更多
It is very necessary for the investigation on mechanism of windblown sand movement to under- stand and find out effective measures of preventing and reducing danger of windblown sands,which al- so deals with some gene...It is very necessary for the investigation on mechanism of windblown sand movement to under- stand and find out effective measures of preventing and reducing danger of windblown sands,which al- so deals with some general characters and hot spots in the scientific forelands,such as multi-scale prob- lems,interactions among multi-physical-fields,ran- domness and nonlinearity as well as complex sys- tems.In recent years,a series of experiments in wind tunnels and theoretical modeling as well as computer simulation have been undertaken in the re- search group of environmental mechanics on wind- blown sand movement in Lanzhou University with the point of mechanical and geography intersecting view.Some original and essential progress has been achieved, which includes that the main regu- larities of charges on sand particles and the electric field in windblown sand flux and the effect of the electric field on the flux and the microwave propaga- tion are revealed,and the evolution process of windblown sand flux under the mutual couple inter- actions among several physical fields are predicted as well as the main features of Aeolian sand ripples are simulated.展开更多
Through the systematic field survey and observations, the factor quantification as well as setting the criteria, the sand disaster-forming environment along the Tarim Desert Highway can be divided into four grades by ...Through the systematic field survey and observations, the factor quantification as well as setting the criteria, the sand disaster-forming environment along the Tarim Desert Highway can be divided into four grades by the classification and regionalization based on fuzzy mathematics. The length of the regions with significant sand disaster accounted for 37.1% of the total highway length. Particularly, the area along the Tarim Desert Highway, based on the sand disaster-forming environment classification as well as the difference in the five basic landform units along the highway, combined with the difference of wind regime, can be divided into five regions, in which the length of the regions suffering severe sand damage occupied 64.3% of the total highway length. In addition, the index of disaster formation grade along the highway decreased from north to south, showing a repeated spatial pattern in small length scales.展开更多
With the PDPA(Phase Doppler Particle Analyzer) measurement technology,the probability distributions of particle impact and lift-off velocities on bed surface and the particle velocity distributions at different height...With the PDPA(Phase Doppler Particle Analyzer) measurement technology,the probability distributions of particle impact and lift-off velocities on bed surface and the particle velocity distributions at different heights are detected in a wind tunnel. The results show that the probability distribution of impact and lift-off velocities of sand grains can be expressed by a log-normal function,and that of impact and lift-off angles complies with an exponential function. The mean impact angle is between 28° and 39°,and the mean lift-off angle ranges from 30° to 44°. The mean lift-off velocity is 0.81-0.9 times the mean impact velocity. The proportion of backward-impacting particles is 0.05-0.11,and that of backward-entrained particles ranges from 0.04 to 0.13. The probability distribution of particle horizontal velocity at 4 mm height is positive skew,the horizontal velocity of particles at 20 mm height varies widely,and the variation of the particle horizontal velocity at 80 mm height is less than that at 20 mm height. The probability distribution of particle vertical velocity at different heights can be described as a normal function.展开更多
A test for the adsorption of cadmium anion with the LongKou windblown coal was carried out.The capacities of windblown coal,the adsorption kinetics,the adsorption models and the effect of pH were studied.The results i...A test for the adsorption of cadmium anion with the LongKou windblown coal was carried out.The capacities of windblown coal,the adsorption kinetics,the adsorption models and the effect of pH were studied.The results indicated that the windblown coal had good adsorption properties to cadmium anion and the adsorption isotherms were consistant with Freundlich equation.展开更多
基金funded by the National Natural Science Foundation of China(11402190)the China Postdoctoral Science foundation(2014M552443)the Shaanxi Province Natural Science Foundation Research Project(2018JM1021)
文摘Windblown sand transport is a leading factor in the geophysical evolution of arid and semi-arid regions.The evolution speed is usually indicated by the sand transport rate that is a function of launch velocity of sand particle,which has been investigated by the experimental measurement and numerical simulation.However,the obtained results in literatures are inconsistent.Some researchers have discovered a relation between average launch velocity and wind shear velocity,while some other researchers have suggested that average launch velocity is independent of wind shear velocity.The inconsistence of launch velocity leads to a controversy in the scaling law of the sand transport rate in the windblown case.On the contrary,in subaqueous case,the scaling law of the sand transport rate has been widely accepted as a cubic function of fluid shear velocity.In order to explain the debates surrounding the windblown case and the difference between windblown and subaquatic cases,this study reinvestigates the scaling law of the vertical launch velocity of windblown transported sand particles by using a dimensional analysis in consideration of the compatibility of the characteristic time of sand particle motion and that of air flow.Then a wind tunnel experiment is conducted to confirm the revisited scaling law,where the sand particle motion pictures are recorded by a high-speed camera and then the launch velocity is solved by the particle tracking velocimetry.By incorporating the results of dimensional analysis and wind tunnel experiment,it can be concluded that,the ratio of saltons number to reptons number determines the scaling law of sand particle launch velocity and that of sand transport rate,and using this ratio is able to explain the discrepancies among the classical models of steady sand transport.Moreover,the resulting scaling law can explain the sand sieving phenomenon:a greater fraction of large grains is observed as the distance to the wind tunnel entrance becomes larger.
基金supported by the National Natural Science Foundation of China (10872082,11002064)the Science Foundation of Ministry of Education of China(308022)
文摘Windblown sand flux and dune field evolving toward the oasis have been a common ecological and environmental threat confronted by many countries.Meanwhile,it is also a kind of complex dynamical process involving multiple temporal and spatial scales which is still out of accurate description through current field observations.Available models and reliable quantitative simulations are of significant value to predict the spreading rate of desertification and provide an optimal design for sand prevention.This paper presents a 'triple-jump' method to realize quantitative simulations to the formation and evolution of an aeolian dune field from an arbitrary initial configuration.Simulated results achieve a satisfactory agreement with observations qualitatively and quantitatively,which also reveal the characteristics and dynamical behaviors of dunes and dune field.Such a paradigm is of a good level of generality,which provides an exploratory probe into the subject of multi-scale physics.
基金supported by the National Natural Science Foundation of China(11072097,11232006,11202088,10972164,and11121202)the Science Foundation of Ministry of Education of China(308022)+1 种基金Science and technology project of Gansu Province(1208RJYA006)National Key Technology R&D Program(2013BAC07B01)
文摘The incipient motion of sand particle from sand bed plays a very important role in the prediction of windblown sand.In this paper,we proposed a new method for predicting the incipient motion of sand particle based on wind speed fluctuation as follows,when the wind speed is larger than the critical wind speed,if the total impulse on sand particle is larger than the critical impulse,incipient motion of sand particle would take place,otherwise if not.Furthermore,from the analysis of entrainment in the rolling and lifting modes,we come to the following conclusion.When the average wind speed is smaller than the critical wind speed,if the average wind speed is used to judge the incipient motion of sand particle,one will underestimate the number of sand particles jumping from the bed,if the instantaneous wind speed is used to judge incipient motion of sand particle,one will overestimate the number of sand particles jumping from the bed;When the average wind speed is larger than the critical wind speed,either the average or the instantaneous wind speeds is used to judge the incipientmotion of sand particles,one will overestimate the number of sand particles jumping from the bed.
文摘It is very necessary for investigation on mechanism of windblown sand movement to understand and find out effective measures of preventing and reducing windblown sand, This also deals with some general features and hot spots in the scientific forelands. such as multi-scale problems. interactions among. multi-physical-fields, randomness and nonlinearity as well as complex systems. In recent years, a series of experiments in wind tunnels and theoretical modeling as well as computer simulation have been taken by our research group （the Laboratory of Environmental Mechanics on Windblown Sand Movement in Lanzhou University ）in a cross-disciplinary （mechanics and geography） viewpoint. Several original and essential studies were explored such as the main regularities of charges on sand particles, the mechanisms of electric field in windblown sand flux, the effects induced by the electric field on the flux, the microwave propagations, the evolution process of windblown and flux under mutual couple interations among several physical fields, and the simulation of the main features of Aeolian sand ripples.
基金the Key Project of the National Natural Science Foundation of China(No.10532040)
文摘It is very necessary for the investigation on mechanism of windblown sand movement to under- stand and find out effective measures of preventing and reducing danger of windblown sands,which al- so deals with some general characters and hot spots in the scientific forelands,such as multi-scale prob- lems,interactions among multi-physical-fields,ran- domness and nonlinearity as well as complex sys- tems.In recent years,a series of experiments in wind tunnels and theoretical modeling as well as computer simulation have been undertaken in the re- search group of environmental mechanics on wind- blown sand movement in Lanzhou University with the point of mechanical and geography intersecting view.Some original and essential progress has been achieved, which includes that the main regu- larities of charges on sand particles and the electric field in windblown sand flux and the effect of the electric field on the flux and the microwave propaga- tion are revealed,and the evolution process of windblown sand flux under the mutual couple inter- actions among several physical fields are predicted as well as the main features of Aeolian sand ripples are simulated.
基金Supported by Major Orientation Foundation of the CAS Innovation Program (Grant No. KZCX3-SW-342)CAS Action-Plan for West Development (Grant No. KZCX2-XB2-13)+3 种基金Major Scientific and Technological Special of Xinjiang Uygur Autonomous Region (Grant No. 200733144-3)National Natural Science Foundation of China (Grant No. 40701019)the research projects of the Tarim Branch of Petro-China Company Limited (Grant Nos. 971008090016 and 971008090017)the Western Light of the Chinese Academy of Sciences (Grant No.20052118)
文摘Through the systematic field survey and observations, the factor quantification as well as setting the criteria, the sand disaster-forming environment along the Tarim Desert Highway can be divided into four grades by the classification and regionalization based on fuzzy mathematics. The length of the regions with significant sand disaster accounted for 37.1% of the total highway length. Particularly, the area along the Tarim Desert Highway, based on the sand disaster-forming environment classification as well as the difference in the five basic landform units along the highway, combined with the difference of wind regime, can be divided into five regions, in which the length of the regions suffering severe sand damage occupied 64.3% of the total highway length. In addition, the index of disaster formation grade along the highway decreased from north to south, showing a repeated spatial pattern in small length scales.
基金the National Natural Science Foundation of China (Grant No. 10532030)the National Basic Research Program of China (Grant No. G2000048702)
文摘With the PDPA(Phase Doppler Particle Analyzer) measurement technology,the probability distributions of particle impact and lift-off velocities on bed surface and the particle velocity distributions at different heights are detected in a wind tunnel. The results show that the probability distribution of impact and lift-off velocities of sand grains can be expressed by a log-normal function,and that of impact and lift-off angles complies with an exponential function. The mean impact angle is between 28° and 39°,and the mean lift-off angle ranges from 30° to 44°. The mean lift-off velocity is 0.81-0.9 times the mean impact velocity. The proportion of backward-impacting particles is 0.05-0.11,and that of backward-entrained particles ranges from 0.04 to 0.13. The probability distribution of particle horizontal velocity at 4 mm height is positive skew,the horizontal velocity of particles at 20 mm height varies widely,and the variation of the particle horizontal velocity at 80 mm height is less than that at 20 mm height. The probability distribution of particle vertical velocity at different heights can be described as a normal function.
文摘A test for the adsorption of cadmium anion with the LongKou windblown coal was carried out.The capacities of windblown coal,the adsorption kinetics,the adsorption models and the effect of pH were studied.The results indicated that the windblown coal had good adsorption properties to cadmium anion and the adsorption isotherms were consistant with Freundlich equation.
