A comparison of three PIV algorithms: FFT-based cross-correlation (FFT-CC) method, direct cross-correlation (DCC) method, and minimum quadratic difference (MQD) method was performed by applying these methods to low nu...A comparison of three PIV algorithms: FFT-based cross-correlation (FFT-CC) method, direct cross-correlation (DCC) method, and minimum quadratic difference (MQD) method was performed by applying these methods to low number density PIV images obtained by the Japan Visualization Society.Raw results of the MQD method were better than those of the FFT-CC, but validated results of the FFT-CC method were better than those of the MQD method. Results of the DCC method were the worst.There was discrepancy between results of the same algorithm with different sizes of the interrogation window.It mainly resulted from various amounts of matched particles of sub images.This study could provide good reference to the selection of the algorithm and its parameters.(展开更多
A computational model combining large .eddy simulation with quadrature moment method was em-ployed to study nanoparticle evolution in a confined impinging jet. The investigated particle size is limited in the transien...A computational model combining large .eddy simulation with quadrature moment method was em-ployed to study nanoparticle evolution in a confined impinging jet. The investigated particle size is limited in the transient regime, and the particle collision kernel was obtained by using the theory of flux matching. The simulation was validated by comparing it with the experimental results. The numerical results show coherent structure acts to dominate particle number intensity, size and polydispersity distributions, and it also induce particle-laden iet to be diluted by .the ambient.The evolution of particle dynarnics in.the impinging jet flow are strongly related to the Rey-nolds number and nozzle-to-plate distance, and their relationships were analyzed.展开更多
A computational study on the flow behavior of a gas-solid injector by Eulerian approach was carried out. The gas phase was modeled with k-ε turbulent model and the particle phase was modeled with kinetic theory of gr...A computational study on the flow behavior of a gas-solid injector by Eulerian approach was carried out. The gas phase was modeled with k-ε turbulent model and the particle phase was modeled with kinetic theory of granular flow. The simulations by Eulerian two-fluid model （TFM） were compared with the corresponding results by discrete element method （DEM） and experiments. It was showed that TFM simulated results were in reasonable agreement with the experimental and DEM simulated results. Based on TFM simulations, gas-solid flow pattern, gas velocity, particle velocity and the static pressure under different driving jet velocity, backpressure and convergent section angle were obtained. The results showed that the time average axial gas velocity sharply decreased and then slightly increased to a constant value in the horizontal conveying pipe. The time average axial particle velocity increased initially and then decreased, but in the outlet region of the convergent section the particle velocity remarkably increased once more to the maximal value. As a whole, the static pressure distribution change trends were found to be independent on driving gas velocity, backpressure and convergent section angle. However, the static pressure increased with increase of convergent section angle and gas jet velocities. The difference of static pressure to backpressure increased with increasing backpressure.展开更多
A mathematical model of the particle heating process in the reaction shaft of flash smelting furnace was established and the calculation was performed.The results indicate that radiation plays a significant role in th...A mathematical model of the particle heating process in the reaction shaft of flash smelting furnace was established and the calculation was performed.The results indicate that radiation plays a significant role in the heat transfer process within the first 0.6 m in the upper part of the reaction shaft,whilst the convection is dominant in the area below 0.6 m for the particle heating.In order to accelerate the particle ignition,it is necessary to enhance the convection,thus to speed up the particle heating.A high-speed preheated oxygen jet technology was then suggested to replace the nature gas combustion in the flash furnace,aiming to create a lateral disturbance in the gaseous phase around the particles,so as to achieve a slip velocity between the two phases and a high convective heat transfer coefficient.Numerical simulation was carried out for the cases with the high-speed oxygen jet and the normal nature gas burners.The results show that with the high-speed jet technology,particles are heated up more rapidly and ignited much earlier,especially within the area of the radial range of R=0.3−0.6 m.As a result,a more efficient smelting process can be achieved under the same operational condition.展开更多
The aim of this study is to examine the effects of local curvature and elastic wall effects of an isothermal hot wall for the purpose of jet impingement cooling performance.Finite element method was used with ALE.Diff...The aim of this study is to examine the effects of local curvature and elastic wall effects of an isothermal hot wall for the purpose of jet impingement cooling performance.Finite element method was used with ALE.Different important parametric effects such as Re number(between 100 and 700),Ha number(between 0 and 20),elasticity(between 104 and 109),curvature of the surface(elliptic,radius ratio between 1 and 0.25) and nanoparticle volume fraction(between 0 and 0.05) on the cooling performance were investigated numerically.The results showed that the average Nu number enhances for higher Hartmann number,higher values of elastic modulus of partly flexible wall and higher nanoparticle volume fraction.When the magnetic field is imposed at the highest strength,there is an increase of3.85% in the average Nu for the curved elastic wall whereas it is 89.22% for the hot part above it,which is due to the vortex suppression effects.Nanoparticle inclusion in the base fluid improves the heat transfer rate by about 27.6% in the absence of magnetic field whereas it is 20.5% under the effects of magnetic field at Ha=20.Curvature effects become important for higher Re numbers and at Re=700,there is 14.11% variation in the average Nu between the cases with the lowest and highest radius ratio.The elastic wall effects on the heat transfer are reduced with the increased curvature of the bottom wall.展开更多
Q-switch for pulsing laser beam and Galvano scanner for rapid scanning laser beam were adapted to manipulate micro solid particles in a water droplet. The trapping of fine particles at micron-sized diameters by a YAG ...Q-switch for pulsing laser beam and Galvano scanner for rapid scanning laser beam were adapted to manipulate micro solid particles in a water droplet. The trapping of fine particles at micron-sized diameters by a YAG laser system, induced flows, and the induced motion of the particles by laser beam irradiations are discussed. Particle rotations are observed by using anisotropic micro objects, and moreover the rotational rate with clockwise direction is 22 r/min. The fragments of a cover glass were mixed in a water droplet, and their size and shape are uneven. The rotation of that non-spheres without scanning by the Galvano scanner is also observed in water.展开更多
文摘A comparison of three PIV algorithms: FFT-based cross-correlation (FFT-CC) method, direct cross-correlation (DCC) method, and minimum quadratic difference (MQD) method was performed by applying these methods to low number density PIV images obtained by the Japan Visualization Society.Raw results of the MQD method were better than those of the FFT-CC, but validated results of the FFT-CC method were better than those of the MQD method. Results of the DCC method were the worst.There was discrepancy between results of the same algorithm with different sizes of the interrogation window.It mainly resulted from various amounts of matched particles of sub images.This study could provide good reference to the selection of the algorithm and its parameters.(
基金Supported by the Ministry of Science and Technology of China (No.2005CCA06900).
文摘A computational model combining large .eddy simulation with quadrature moment method was em-ployed to study nanoparticle evolution in a confined impinging jet. The investigated particle size is limited in the transient regime, and the particle collision kernel was obtained by using the theory of flux matching. The simulation was validated by comparing it with the experimental results. The numerical results show coherent structure acts to dominate particle number intensity, size and polydispersity distributions, and it also induce particle-laden iet to be diluted by .the ambient.The evolution of particle dynarnics in.the impinging jet flow are strongly related to the Rey-nolds number and nozzle-to-plate distance, and their relationships were analyzed.
基金Supported by the National High Technology Research and Development Program of China （2006AA05A103）, the National Natural Science Foundation of China （50706007）, Foundation of Graduate Creative Program of Jiangsu （CX08B-060Z）, and the Foundation for Excellent Ph.D. Thesis of Southeast University. ACKNOWLEDGEMENTS The authors also expressed sincere gratitude to Professors M. Horio, B. Leckner, A. Kane and E.J. Anthony for constructive advice during their visiting period in Southeast University, which contributed to our research.
文摘A computational study on the flow behavior of a gas-solid injector by Eulerian approach was carried out. The gas phase was modeled with k-ε turbulent model and the particle phase was modeled with kinetic theory of granular flow. The simulations by Eulerian two-fluid model （TFM） were compared with the corresponding results by discrete element method （DEM） and experiments. It was showed that TFM simulated results were in reasonable agreement with the experimental and DEM simulated results. Based on TFM simulations, gas-solid flow pattern, gas velocity, particle velocity and the static pressure under different driving jet velocity, backpressure and convergent section angle were obtained. The results showed that the time average axial gas velocity sharply decreased and then slightly increased to a constant value in the horizontal conveying pipe. The time average axial particle velocity increased initially and then decreased, but in the outlet region of the convergent section the particle velocity remarkably increased once more to the maximal value. As a whole, the static pressure distribution change trends were found to be independent on driving gas velocity, backpressure and convergent section angle. However, the static pressure increased with increase of convergent section angle and gas jet velocities. The difference of static pressure to backpressure increased with increasing backpressure.
基金funded by Jinguan Copper of Tongling Non-ferrous Metals Group Co., Ltd.
文摘A mathematical model of the particle heating process in the reaction shaft of flash smelting furnace was established and the calculation was performed.The results indicate that radiation plays a significant role in the heat transfer process within the first 0.6 m in the upper part of the reaction shaft,whilst the convection is dominant in the area below 0.6 m for the particle heating.In order to accelerate the particle ignition,it is necessary to enhance the convection,thus to speed up the particle heating.A high-speed preheated oxygen jet technology was then suggested to replace the nature gas combustion in the flash furnace,aiming to create a lateral disturbance in the gaseous phase around the particles,so as to achieve a slip velocity between the two phases and a high convective heat transfer coefficient.Numerical simulation was carried out for the cases with the high-speed oxygen jet and the normal nature gas burners.The results show that with the high-speed jet technology,particles are heated up more rapidly and ignited much earlier,especially within the area of the radial range of R=0.3−0.6 m.As a result,a more efficient smelting process can be achieved under the same operational condition.
文摘The aim of this study is to examine the effects of local curvature and elastic wall effects of an isothermal hot wall for the purpose of jet impingement cooling performance.Finite element method was used with ALE.Different important parametric effects such as Re number(between 100 and 700),Ha number(between 0 and 20),elasticity(between 104 and 109),curvature of the surface(elliptic,radius ratio between 1 and 0.25) and nanoparticle volume fraction(between 0 and 0.05) on the cooling performance were investigated numerically.The results showed that the average Nu number enhances for higher Hartmann number,higher values of elastic modulus of partly flexible wall and higher nanoparticle volume fraction.When the magnetic field is imposed at the highest strength,there is an increase of3.85% in the average Nu for the curved elastic wall whereas it is 89.22% for the hot part above it,which is due to the vortex suppression effects.Nanoparticle inclusion in the base fluid improves the heat transfer rate by about 27.6% in the absence of magnetic field whereas it is 20.5% under the effects of magnetic field at Ha=20.Curvature effects become important for higher Re numbers and at Re=700,there is 14.11% variation in the average Nu between the cases with the lowest and highest radius ratio.The elastic wall effects on the heat transfer are reduced with the increased curvature of the bottom wall.
文摘Q-switch for pulsing laser beam and Galvano scanner for rapid scanning laser beam were adapted to manipulate micro solid particles in a water droplet. The trapping of fine particles at micron-sized diameters by a YAG laser system, induced flows, and the induced motion of the particles by laser beam irradiations are discussed. Particle rotations are observed by using anisotropic micro objects, and moreover the rotational rate with clockwise direction is 22 r/min. The fragments of a cover glass were mixed in a water droplet, and their size and shape are uneven. The rotation of that non-spheres without scanning by the Galvano scanner is also observed in water.
