The construction and hydrogeological area in the low hill, which is northwest of Laixi City and in the east of Shandong Province more precisely, is one of Dagu River's groundwater source. Regarding COD as the typi...The construction and hydrogeological area in the low hill, which is northwest of Laixi City and in the east of Shandong Province more precisely, is one of Dagu River's groundwater source. Regarding COD as the typical pollutant according to general situation of groundwater pollution in aforementioned area, a three-dimensional advection-dispersion model was established to simulate the transport of organic pollutants under two accident conditions. In addition, the effect of corresponding dispersity was analyzed. The results show that COD transport is mainly in accordance with the direction of groundwater flow, pollutant concentration and its gradient as well as the rule of narrower pollution range in deeper stratum. Moreover, COD is mainly transported and diffused in groundwater of sandy soil in the first and second layers. However, under accident condition II, the pollutant concentration begins to decay gradually after its transport and diffusion tends to be stable. Besides, in terms of dominance, dispersion is to transverse transport of pollutants what advection is to longitudinal transport. If considering random dispersion, the final results see higher peak concentration of COD and longer transverse distance from pollution center compared to transport route. What's more, the pollution plume changes and concentration isocline becomes slightly irregular.展开更多
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
The purpose is to reestablish the coupled conservation laws, the local conservation equations and the jump conditions of mass and inertia for polar continuum theories. In this connection the new material derivatives o...The purpose is to reestablish the coupled conservation laws, the local conservation equations and the jump conditions of mass and inertia for polar continuum theories. In this connection the new material derivatives of the deformation gradient, the line element, the surface element and the volume element were derived and the generalized Reynolds transport theorem was presented. Combining these conservation laws of mass and inertia with the balance laws of momentum, angular momentum and energy derived in our previous papers of this series, a rather complete system of coupled basic laws and principles for polar continuum theories is constituted on the whole. From this system the coupled nonlocal balance equations of mass, inertia, momentum, angular momentum and energy may be obtained by the usual localization.展开更多
The erythrocyte and blood flowing in the blood vessel can be treated as the two-phase flow of the mixture of particles and a power-law fluid in a peristaltic tube.In the present work, the peristaltic transport of a po...The erythrocyte and blood flowing in the blood vessel can be treated as the two-phase flow of the mixture of particles and a power-law fluid in a peristaltic tube.In the present work, the peristaltic transport of a power-law fluid and the suspension of particles in a tube is investigated by a perturbation method using the long wavelength approximation. The influence of different parameters on the velocity profile and streamlines is explored. Results show that there is a deflection of the flow field when the power-law index n = 0.5 or 1.5 compared with the Newtonian fluid where the trapping zone is symmetric to a certain cross section. The flux rate and reflux of the material are identified,and the conditions under which the reflux appears are determined. Moreover, a reflux phenomenon occurs near the wall. The trapping zone is related to not only the tube geometry and the flow flux but also the fluid properties. Both the length and width of the trapping zone increase with an increase in θ or φ. The trapping zone is more difficult to produce in the shear-thinning fluid than the shear-thickening fluid.展开更多
The evolution characteristics of bedload transport feature of paroxysm debris flow have been studied by means of both theory analysis and experimental data.The analysis based on the flume experiment data of a sand pil...The evolution characteristics of bedload transport feature of paroxysm debris flow have been studied by means of both theory analysis and experimental data.The analysis based on the flume experiment data of a sand pile model as well as a large amount of field data of debris flow clearly shown that the statistical distribu- tion for the main variable of the sand pile made of non-uniform sand (according the sand pile experiment,φ≥2.55) conform to the negative power law,that means the non-uniform sand syste...展开更多
文摘The construction and hydrogeological area in the low hill, which is northwest of Laixi City and in the east of Shandong Province more precisely, is one of Dagu River's groundwater source. Regarding COD as the typical pollutant according to general situation of groundwater pollution in aforementioned area, a three-dimensional advection-dispersion model was established to simulate the transport of organic pollutants under two accident conditions. In addition, the effect of corresponding dispersity was analyzed. The results show that COD transport is mainly in accordance with the direction of groundwater flow, pollutant concentration and its gradient as well as the rule of narrower pollution range in deeper stratum. Moreover, COD is mainly transported and diffused in groundwater of sandy soil in the first and second layers. However, under accident condition II, the pollutant concentration begins to decay gradually after its transport and diffusion tends to be stable. Besides, in terms of dominance, dispersion is to transverse transport of pollutants what advection is to longitudinal transport. If considering random dispersion, the final results see higher peak concentration of COD and longer transverse distance from pollution center compared to transport route. What's more, the pollution plume changes and concentration isocline becomes slightly irregular.
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.
文摘The purpose is to reestablish the coupled conservation laws, the local conservation equations and the jump conditions of mass and inertia for polar continuum theories. In this connection the new material derivatives of the deformation gradient, the line element, the surface element and the volume element were derived and the generalized Reynolds transport theorem was presented. Combining these conservation laws of mass and inertia with the balance laws of momentum, angular momentum and energy derived in our previous papers of this series, a rather complete system of coupled basic laws and principles for polar continuum theories is constituted on the whole. From this system the coupled nonlocal balance equations of mass, inertia, momentum, angular momentum and energy may be obtained by the usual localization.
基金supported by the Major Program of National Natural Science Foundation of China(Nos.11632016 and 91634103)
文摘The erythrocyte and blood flowing in the blood vessel can be treated as the two-phase flow of the mixture of particles and a power-law fluid in a peristaltic tube.In the present work, the peristaltic transport of a power-law fluid and the suspension of particles in a tube is investigated by a perturbation method using the long wavelength approximation. The influence of different parameters on the velocity profile and streamlines is explored. Results show that there is a deflection of the flow field when the power-law index n = 0.5 or 1.5 compared with the Newtonian fluid where the trapping zone is symmetric to a certain cross section. The flux rate and reflux of the material are identified,and the conditions under which the reflux appears are determined. Moreover, a reflux phenomenon occurs near the wall. The trapping zone is related to not only the tube geometry and the flow flux but also the fluid properties. Both the length and width of the trapping zone increase with an increase in θ or φ. The trapping zone is more difficult to produce in the shear-thinning fluid than the shear-thickening fluid.
基金Supported by the National Natureal Science Foundation of China (5040901240025103)
文摘The evolution characteristics of bedload transport feature of paroxysm debris flow have been studied by means of both theory analysis and experimental data.The analysis based on the flume experiment data of a sand pile model as well as a large amount of field data of debris flow clearly shown that the statistical distribu- tion for the main variable of the sand pile made of non-uniform sand (according the sand pile experiment,φ≥2.55) conform to the negative power law,that means the non-uniform sand syste...
