An experimental study was conducted to investigate the evolutions of unsteady vortex structures downstream a lobed mixer/nozzle.A novel dual-plane stereoscopic PIV system was used to measure all 3-components of vortic...An experimental study was conducted to investigate the evolutions of unsteady vortex structures downstream a lobed mixer/nozzle.A novel dual-plane stereoscopic PIV system was used to measure all 3-components of vorticity distributions to revealed both the large-scale streamwise vortices produced by the lobed mixer/nozzle and the Kelvin-Helmholtz vortex structures generated due to the Kelvin-Helmholtz instabilities simultaneously and quantitatively for the first time.The instantaneous and the ensemble-averaged vorticity distributions displayed quite different aspects about the evolutions of the unsteady vortex structures.While the ensemble-averaged vorticity distributions indicated the overall effect of the special geometry of the lobed nozzle/mixer on the enhanced mixing process,the instantaneous vorticity distributions elucidated many details about how the enhanced mixing process was conducted.In addition to quantitatively confirming conjectures of previous studies,further insight about the formation,evolution and interaction characteristics of the unsteady vortex structures downstream of the lobed mixer/nozzle were also uncovered quantitatively in the present study.展开更多
Stabilizing the interface wave of the molten aluminum(metal)-electrolyte(bath)is beneficial to shorten the anode-cathode distance(ACD)which is critical to the energy saving.A coupled mathematical model was developed t...Stabilizing the interface wave of the molten aluminum(metal)-electrolyte(bath)is beneficial to shorten the anode-cathode distance(ACD)which is critical to the energy saving.A coupled mathematical model was developed to study the impact of the novel cathode protrusion on the molten fluid motion as well as the metal-bath interface deformation.The molten fluid motion in the aluminum reduction ceils is under the combined effect of the electro-magnetic forces(EMFs)and the gas bubbles generated at the anode.A transient inhomogeneous three-phase model(metal-bath-gas bubble)was established in order to calculate more accurate.The results indicate that the metal-bath interface deformation can be reduced significantly by the novel cathode protrusion which is beneficial to the electric energy saving.Besides,The EMFs decreases as a result of the optimizing of the magnetic field due to the novel cathode convex which is an important driving force for the deformation of the interface.In addition,large vortex in the metal flow field is break up into the small vortex by the cathode protrusion and then dissipated due to the viscous force and the hindering effect of the cathode protrusion.The quantity of the vortex as well as the strength of the vortex reduces significantly in the reduction cell with novel cathode protrusion.展开更多
To reduce the complexity of mixing systems and improve mixing efficiency,this paper proposes a valveless piezoelectric pump integrated with airfoil baffles,which embodies both active and passive mixing attributes.The ...To reduce the complexity of mixing systems and improve mixing efficiency,this paper proposes a valveless piezoelectric pump integrated with airfoil baffles,which embodies both active and passive mixing attributes.The airfoil baffles are designed using the asymmetric NACA63-412 profile.The impact of the airfoil angle of attack on the flow field within the tube and the output and mixing performance of the piezoelectric pump is investigated.Computational simulations of the tube with airfoil baffle indicated that as the angle of attack increases,the position of vortex generation at the leading and trailing edge regions of the airfoil baffle progressively moves forward in the direction of fluid flow.Then the vortex volume enlarges,and the vortex intensity within the flow field rises.Subsequently,the prototypes of valveless piezoelectric pumps at four different angles of attack are fabricated and their output performances are experimentally evaluated.The results demonstrate that the maximum output flow rate of the pump decreases with an increasing angle of attack.At an angle of attack of 0°,the maximum output flow rate of the pump reaches 225.3 ml/min.Mixing performance experiments are conducted using the piezoelectric pump for the synthesis of Fe_(3)O_(4)particles.The findings indicate that as the angle of attack increases,the number of Fe_(3)O_(4)particles formed in the mixture significantly rises,with a narrower particle size distribution and more regular morphology.At an angle of attack of 15°,the synthesized Fe_(3)O_(4)particles have an approximate diameter of 10μm.The outcomes of this paper offer valuable insights for the design of microfluidic systems,catering to the demands of material synthesis,chemistry,and biomedical applications.展开更多
文摘An experimental study was conducted to investigate the evolutions of unsteady vortex structures downstream a lobed mixer/nozzle.A novel dual-plane stereoscopic PIV system was used to measure all 3-components of vorticity distributions to revealed both the large-scale streamwise vortices produced by the lobed mixer/nozzle and the Kelvin-Helmholtz vortex structures generated due to the Kelvin-Helmholtz instabilities simultaneously and quantitatively for the first time.The instantaneous and the ensemble-averaged vorticity distributions displayed quite different aspects about the evolutions of the unsteady vortex structures.While the ensemble-averaged vorticity distributions indicated the overall effect of the special geometry of the lobed nozzle/mixer on the enhanced mixing process,the instantaneous vorticity distributions elucidated many details about how the enhanced mixing process was conducted.In addition to quantitatively confirming conjectures of previous studies,further insight about the formation,evolution and interaction characteristics of the unsteady vortex structures downstream of the lobed mixer/nozzle were also uncovered quantitatively in the present study.
基金Item Sponsored by the National Natural Science Foundation of China[NO.50934005 and NO.50904014]
文摘Stabilizing the interface wave of the molten aluminum(metal)-electrolyte(bath)is beneficial to shorten the anode-cathode distance(ACD)which is critical to the energy saving.A coupled mathematical model was developed to study the impact of the novel cathode protrusion on the molten fluid motion as well as the metal-bath interface deformation.The molten fluid motion in the aluminum reduction ceils is under the combined effect of the electro-magnetic forces(EMFs)and the gas bubbles generated at the anode.A transient inhomogeneous three-phase model(metal-bath-gas bubble)was established in order to calculate more accurate.The results indicate that the metal-bath interface deformation can be reduced significantly by the novel cathode protrusion which is beneficial to the electric energy saving.Besides,The EMFs decreases as a result of the optimizing of the magnetic field due to the novel cathode convex which is an important driving force for the deformation of the interface.In addition,large vortex in the metal flow field is break up into the small vortex by the cathode protrusion and then dissipated due to the viscous force and the hindering effect of the cathode protrusion.The quantity of the vortex as well as the strength of the vortex reduces significantly in the reduction cell with novel cathode protrusion.
基金supported by the National Natural Science Foundation of China(Nos.51605200,52206045)。
文摘To reduce the complexity of mixing systems and improve mixing efficiency,this paper proposes a valveless piezoelectric pump integrated with airfoil baffles,which embodies both active and passive mixing attributes.The airfoil baffles are designed using the asymmetric NACA63-412 profile.The impact of the airfoil angle of attack on the flow field within the tube and the output and mixing performance of the piezoelectric pump is investigated.Computational simulations of the tube with airfoil baffle indicated that as the angle of attack increases,the position of vortex generation at the leading and trailing edge regions of the airfoil baffle progressively moves forward in the direction of fluid flow.Then the vortex volume enlarges,and the vortex intensity within the flow field rises.Subsequently,the prototypes of valveless piezoelectric pumps at four different angles of attack are fabricated and their output performances are experimentally evaluated.The results demonstrate that the maximum output flow rate of the pump decreases with an increasing angle of attack.At an angle of attack of 0°,the maximum output flow rate of the pump reaches 225.3 ml/min.Mixing performance experiments are conducted using the piezoelectric pump for the synthesis of Fe_(3)O_(4)particles.The findings indicate that as the angle of attack increases,the number of Fe_(3)O_(4)particles formed in the mixture significantly rises,with a narrower particle size distribution and more regular morphology.At an angle of attack of 15°,the synthesized Fe_(3)O_(4)particles have an approximate diameter of 10μm.The outcomes of this paper offer valuable insights for the design of microfluidic systems,catering to the demands of material synthesis,chemistry,and biomedical applications.
