Considering the droplet coalescence, the motion of a group of dispersed droplets in W/O emulsion in a DC electric field is simulated. The simulation demonstrates the evolutions of droplet number, size as well as its d...Considering the droplet coalescence, the motion of a group of dispersed droplets in W/O emulsion in a DC electric field is simulated. The simulation demonstrates the evolutions of droplet number, size as well as its distribution,local concentration distribution and droplet size-velocity relation with the applied time of electric field. The simulated average droplet size is roughly consistent with the experimental value. The simulated variation of droplet number with time under several applied voltages shows that increasing voltage is more effective for raising the rate of droplet coalescence than extending exerting time. However, with the further raise of applied voltage, the improvement in droplet coalescence rate becomes less significant. The evolution of simulated droplet size–velocity relationship with time shows that the inter-droplet electric repulsion force is very strong due to larger electric charge on the droplet under higher applied voltage, so that the magnitude and the direction of droplet velocity become more random, which looks helpful to droplet coalescence.展开更多
To investigate the impacts of the quasi-biennial oscillation （QBO） on high-latitude circulation and the Arctic vortex, stratospheric zonal wind at 55-65°N is analyzed. The seasonal cycle, solar cycle, and linea...To investigate the impacts of the quasi-biennial oscillation （QBO） on high-latitude circulation and the Arctic vortex, stratospheric zonal wind at 55-65°N is analyzed. The seasonal cycle, solar cycle, and linear trend in the zonal wind at these latitudes are analyzed and removed, and the QBO signal is retrieved from the monthly zonal wind for the period 1979-2014. The zonal wind has a strong decreasing trend in winter, with a maximum decrease （less than -0.35 m s-1 yr-1） occurring within 70-100°E. The zonal wind has an in-phase response of 1.6 m s-1 to the solar cycle, with a maximum within 100-140°E. A clear QBO signal is detected in the zonal wind during the period 1979-2014, with an amplitude of 2.5 m s-1 and a period of 30 months. The latitudinal distribution of the QBO signal is inhomogeneous, with a maximum within 120-180°E and a minimum within 25-45°E.展开更多
The radial tidal current field accounts for the formation of the radial sand ridges in the South Yellow Sea. Understanding the formation and evolution of this radial tidal current field is vital to assessing the morph...The radial tidal current field accounts for the formation of the radial sand ridges in the South Yellow Sea. Understanding the formation and evolution of this radial tidal current field is vital to assessing the morphodynamic features in the area. A semi-enclosed rectangular basin with and without a coastal barrier was schematized from the topography of the Bohai Sea and Yellow Sea. The 2D tidal current field in this basin was simulated using the DELFT3D-FLOW model. The concept of tidal wave refraction, which highlights the effect of the sloped or stepped submarine topography on the propagation of the tidal waves, was introduced to explain the formation of the radial tidal current field. Under the effect of tidal wave refraction, co-phase lines of the counterclockwise rotating tidal wave and incident tidal wave are transformed into clockwise and counterclockwise deflections, respectively, leading to the convergence and divergence of the flow field. Regardless of whether a coastal barrier exists or not, the outer radial tidal current field might emerge over certain topography. The responses of the radial tidal current field in this basin to the environmental variations such as coastline changes and bottom erosions were discussed. Results show that local protrusion near the focal point of the radial tidal current field will have limited effects on the location of the tidal system. However, a remarkable shift of the amphidromic point toward the entrance and central axis of this basin and a movement of the focal point of the radial tidal current field toward the entrance could be caused by the significant seaward coastline advance and submarine slope erosion.展开更多
The rotating pipe fluid in the crossed electric and magnetic field not only suffered the forces in the steady condition, but also suffered Coriolis force, centrifugal force because of rotation and electromagnetic volu...The rotating pipe fluid in the crossed electric and magnetic field not only suffered the forces in the steady condition, but also suffered Coriolis force, centrifugal force because of rotation and electromagnetic volume force. The motion equation of fluid and the hydrokinetics equations of rotating pipe were described in the Cartesians coordinates. The equations showed that the solutions to hydrokinetics equations of rotating pipe in the crossed electric and magnetic electromagnetic field were highly complicated and numerical calculations were also astronomical. The pressure distribution and temperature distribution of one dimension were solved using the electromagnetic equations set. The results showed that the fluid in rotating pipe was in the asymmetrical pressure field and temperature field because it was in the energy exchange and thermo-electrical coupling course. The primary characteristic of flow course could be expressed using the proposed hydrokinetics equations.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
Air pollution caused by particles with small size has been a global concern because of threats to human health.A feasible way to remove these super fine suspended particles is using electrostatic precipitation technol...Air pollution caused by particles with small size has been a global concern because of threats to human health.A feasible way to remove these super fine suspended particles is using electrostatic precipitation technology.Herein,the PIV was used to measure the particle velocity distribution.By analyzing the particle motion trend in high electric field,a process of particle charging loss was observed.This phenomenon cannot be explained by current particle charging theories.Our conclusions may improve the understanding of particle charging processes.展开更多
An analysis is carried out to study the steady flow characteristics from a continuous flat surface moving in a parallel free stream of non-Newtonian power law fluid. The constitutive equations of the fluid are transfo...An analysis is carried out to study the steady flow characteristics from a continuous flat surface moving in a parallel free stream of non-Newtonian power law fluid. The constitutive equations of the fluid are transformed into dimensionless ones. The velocity field is measured by Particle Image Velocimetry. Experimental results are obtained for the distribution of velocity. The influence of wall velocity ratio parameter on boundary layer flow field is observed in the experiment. Dimensionless velocity distribution and shearing stress distribution are obtained by post-processing experimental results. The effects of various physical parameters like velocity ratio parameter and similarity variable on various momentum transfer characteristics are discussed in detail and shown graphically. It is indicated that dimensionless velocity increases with velocity ratio parameter and similarity variable, and that dimensionless shearing stress decreases with velocity ratio parameter and similarity variable.展开更多
We present an experimental study on the motion of a spherical droplet in a plane traveling sound wave.The experiments were performed in the test section of a tunnel with two loudspeakers at the two ends of the tunnel....We present an experimental study on the motion of a spherical droplet in a plane traveling sound wave.The experiments were performed in the test section of a tunnel with two loudspeakers at the two ends of the tunnel.By adjusting the amplitude ratio and the phase difference between the two speakers,a plane traveling sound wave field can be achieved in the test section of the tunnel,which we checked by measuring the amplitudes and phases of the sound pressure along the tunnel and by simultaneously measuring the velocity field of the air flow at three different locations in the tunnel.When a liquid droplet was introduced in the test section,the motion of the droplet and the velocity of the air flow around the droplet were recorded by high speed cameras,from which we analyze and obtain the ratio of the velocity amplitudes and the phase difference between the particle motion and the fluid motion.The experimental data confirm the theoretical result from the wave equations in the long-wavelength regime,i.e.,when the particle size is much smaller than the wavelength.Moreover,we showed that in this regime,the theory on particle motion in an unsteady uniform fluid,when the history term is included,also yields the same results that are in agreement with the experimental data and the wave equation.Our result extends the parameter range over which the theory on particle motion in unsteady fluid is checked against experiments,especially to the range of particle-fluid density ratio that is of important practical applications.展开更多
基金Supported by the Special Research Project of Fujian Province(JK2012027)the Natural Science Foundation of Fujian Province(2014J01201)
文摘Considering the droplet coalescence, the motion of a group of dispersed droplets in W/O emulsion in a DC electric field is simulated. The simulation demonstrates the evolutions of droplet number, size as well as its distribution,local concentration distribution and droplet size-velocity relation with the applied time of electric field. The simulated average droplet size is roughly consistent with the experimental value. The simulated variation of droplet number with time under several applied voltages shows that increasing voltage is more effective for raising the rate of droplet coalescence than extending exerting time. However, with the further raise of applied voltage, the improvement in droplet coalescence rate becomes less significant. The evolution of simulated droplet size–velocity relationship with time shows that the inter-droplet electric repulsion force is very strong due to larger electric charge on the droplet under higher applied voltage, so that the magnitude and the direction of droplet velocity become more random, which looks helpful to droplet coalescence.
基金supported by the Special Fund for Meteorological Research in the Public Interest[grant number GYHY201206041]the projects entitled‘Comprehensive Evaluation of Polar Areas in Global and Regional Climate Changes’[grant number CHINARE2015–2019]‘Polar Environment Comprehensive Investigation and Assessment’[grant number CHINARE2015–2019]
文摘To investigate the impacts of the quasi-biennial oscillation （QBO） on high-latitude circulation and the Arctic vortex, stratospheric zonal wind at 55-65°N is analyzed. The seasonal cycle, solar cycle, and linear trend in the zonal wind at these latitudes are analyzed and removed, and the QBO signal is retrieved from the monthly zonal wind for the period 1979-2014. The zonal wind has a strong decreasing trend in winter, with a maximum decrease （less than -0.35 m s-1 yr-1） occurring within 70-100°E. The zonal wind has an in-phase response of 1.6 m s-1 to the solar cycle, with a maximum within 100-140°E. A clear QBO signal is detected in the zonal wind during the period 1979-2014, with an amplitude of 2.5 m s-1 and a period of 30 months. The latitudinal distribution of the QBO signal is inhomogeneous, with a maximum within 120-180°E and a minimum within 25-45°E.
基金Supported by the National Natural Science Foundation of China(Nos.51179067,51379072)the Special Funds for Scientific Research on Public Welfare of Ministry of Water Resources of China(No.201201045)the College Graduate Research and Innovation Project of Jiangsu Province,China(No.CXZZ12_0254)
文摘The radial tidal current field accounts for the formation of the radial sand ridges in the South Yellow Sea. Understanding the formation and evolution of this radial tidal current field is vital to assessing the morphodynamic features in the area. A semi-enclosed rectangular basin with and without a coastal barrier was schematized from the topography of the Bohai Sea and Yellow Sea. The 2D tidal current field in this basin was simulated using the DELFT3D-FLOW model. The concept of tidal wave refraction, which highlights the effect of the sloped or stepped submarine topography on the propagation of the tidal waves, was introduced to explain the formation of the radial tidal current field. Under the effect of tidal wave refraction, co-phase lines of the counterclockwise rotating tidal wave and incident tidal wave are transformed into clockwise and counterclockwise deflections, respectively, leading to the convergence and divergence of the flow field. Regardless of whether a coastal barrier exists or not, the outer radial tidal current field might emerge over certain topography. The responses of the radial tidal current field in this basin to the environmental variations such as coastline changes and bottom erosions were discussed. Results show that local protrusion near the focal point of the radial tidal current field will have limited effects on the location of the tidal system. However, a remarkable shift of the amphidromic point toward the entrance and central axis of this basin and a movement of the focal point of the radial tidal current field toward the entrance could be caused by the significant seaward coastline advance and submarine slope erosion.
文摘The rotating pipe fluid in the crossed electric and magnetic field not only suffered the forces in the steady condition, but also suffered Coriolis force, centrifugal force because of rotation and electromagnetic volume force. The motion equation of fluid and the hydrokinetics equations of rotating pipe were described in the Cartesians coordinates. The equations showed that the solutions to hydrokinetics equations of rotating pipe in the crossed electric and magnetic electromagnetic field were highly complicated and numerical calculations were also astronomical. The pressure distribution and temperature distribution of one dimension were solved using the electromagnetic equations set. The results showed that the fluid in rotating pipe was in the asymmetrical pressure field and temperature field because it was in the energy exchange and thermo-electrical coupling course. The primary characteristic of flow course could be expressed using the proposed hydrokinetics equations.
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 the National Natural Science Foundation of China(Grant No.51107095)
文摘Air pollution caused by particles with small size has been a global concern because of threats to human health.A feasible way to remove these super fine suspended particles is using electrostatic precipitation technology.Herein,the PIV was used to measure the particle velocity distribution.By analyzing the particle motion trend in high electric field,a process of particle charging loss was observed.This phenomenon cannot be explained by current particle charging theories.Our conclusions may improve the understanding of particle charging processes.
基金supported by the National Natural Science Foundation of China (No. 50476083)
文摘An analysis is carried out to study the steady flow characteristics from a continuous flat surface moving in a parallel free stream of non-Newtonian power law fluid. The constitutive equations of the fluid are transformed into dimensionless ones. The velocity field is measured by Particle Image Velocimetry. Experimental results are obtained for the distribution of velocity. The influence of wall velocity ratio parameter on boundary layer flow field is observed in the experiment. Dimensionless velocity distribution and shearing stress distribution are obtained by post-processing experimental results. The effects of various physical parameters like velocity ratio parameter and similarity variable on various momentum transfer characteristics are discussed in detail and shown graphically. It is indicated that dimensionless velocity increases with velocity ratio parameter and similarity variable, and that dimensionless shearing stress decreases with velocity ratio parameter and similarity variable.
基金This work was supported partially by the National Natural Science Foundation of China(Grant No.11988102)and by Tsinghua University.
文摘We present an experimental study on the motion of a spherical droplet in a plane traveling sound wave.The experiments were performed in the test section of a tunnel with two loudspeakers at the two ends of the tunnel.By adjusting the amplitude ratio and the phase difference between the two speakers,a plane traveling sound wave field can be achieved in the test section of the tunnel,which we checked by measuring the amplitudes and phases of the sound pressure along the tunnel and by simultaneously measuring the velocity field of the air flow at three different locations in the tunnel.When a liquid droplet was introduced in the test section,the motion of the droplet and the velocity of the air flow around the droplet were recorded by high speed cameras,from which we analyze and obtain the ratio of the velocity amplitudes and the phase difference between the particle motion and the fluid motion.The experimental data confirm the theoretical result from the wave equations in the long-wavelength regime,i.e.,when the particle size is much smaller than the wavelength.Moreover,we showed that in this regime,the theory on particle motion in an unsteady uniform fluid,when the history term is included,also yields the same results that are in agreement with the experimental data and the wave equation.Our result extends the parameter range over which the theory on particle motion in unsteady fluid is checked against experiments,especially to the range of particle-fluid density ratio that is of important practical applications.
