Dynamics and vibration of control valves under flow-induced vibration are analyzed. Hydrodynamic load characteristics and structural response under flow-induced vibration are mainly influenced by inertia, damping, ela...Dynamics and vibration of control valves under flow-induced vibration are analyzed. Hydrodynamic load characteristics and structural response under flow-induced vibration are mainly influenced by inertia, damping, elastic, geometric characteristics and hydraulic parameters. The purpose of this work is to investigate the dynamic behavior of control valves in the response to self-excited fluid flow. An analytical and numerical method is developed to simulate the dynamic and vibrational behavior of sliding dam valves, in response to flow excitation. In order to demonstrate the effectiveness of proposed model, the simulation results are validated with experimental ones. Finally, to achieve the optimal valve geometry, numerical results for various shapes of valves are compared. Rounded valve with the least amount of flow turbulence obtains lower fluctuations and vibration amplitude compared with the flat and steep valves. Simulation results demonstrate that with the optimal design requirements of valves, vibration amplitude can be reduced by an average to 30%.展开更多
The current responses of a generation/collection (G/C) system based on dual micropipettes are simulated by the boundary element (BE) method, from which the collection efficiencies for various pipettes with different g...The current responses of a generation/collection (G/C) system based on dual micropipettes are simulated by the boundary element (BE) method, from which the collection efficiencies for various pipettes with different geometries are calculated. The influence of the shape of a dual micropipette on the collection efficiency, such as curvature and symmetry of the pipette, as well as the thickness of glassy band between generator and collector, is presented and discussed in detail. Moreover, the simulation results have been tested using the experiments of potassium and sodium ions transfers facilitated by dibenzo-18-crown-6 (DB18C6) at the water/1,2-dichloroethane (W/DCE) interface. These results demonstrate that the BE method is an efficient and useful approach for the simulation of collection efficiency of symmetric geometries of dual micropipettes operating in the G/C mode under transport conditions of diffusion control. However, there are still some problems for the cases of asymmetric dual micropipettes, which show rather large differences between the values of simulated and experimental ones. This work also indicates that such an ionic G/C technique should have advantages in applications when the dual pipettes have symmetric geometries.展开更多
Dislocation dynamics simulations are performed to investigate the effect of template shape on the nanoimprinting of metal layers. To this end, metal thin films are imprinted by a rigid template made of an array of equ...Dislocation dynamics simulations are performed to investigate the effect of template shape on the nanoimprinting of metal layers. To this end, metal thin films are imprinted by a rigid template made of an array of equispaced indenters of various shapes, i.e., rectangular, wedge, and circular. The geometry of the indenters is chosen such that the contact area is approximately the same at the final imprinting depth. Results show that, for all template shapes, the final patterns strongly depend on the dislocation activity, and that each imprint differs from the neighboring ones. Large material pile ups appear between the imprints, such that polishing of the metal layer is suggested for application of the patterns in electronics. Rectangular indenters require the lowest imprinting force and achieve the deepest retained imprints.展开更多
文摘Dynamics and vibration of control valves under flow-induced vibration are analyzed. Hydrodynamic load characteristics and structural response under flow-induced vibration are mainly influenced by inertia, damping, elastic, geometric characteristics and hydraulic parameters. The purpose of this work is to investigate the dynamic behavior of control valves in the response to self-excited fluid flow. An analytical and numerical method is developed to simulate the dynamic and vibrational behavior of sliding dam valves, in response to flow excitation. In order to demonstrate the effectiveness of proposed model, the simulation results are validated with experimental ones. Finally, to achieve the optimal valve geometry, numerical results for various shapes of valves are compared. Rounded valve with the least amount of flow turbulence obtains lower fluctuations and vibration amplitude compared with the flat and steep valves. Simulation results demonstrate that with the optimal design requirements of valves, vibration amplitude can be reduced by an average to 30%.
基金supported by the National Natural Science Foundation of China (20735001, 21075004, 60372024 & 60532080)
文摘The current responses of a generation/collection (G/C) system based on dual micropipettes are simulated by the boundary element (BE) method, from which the collection efficiencies for various pipettes with different geometries are calculated. The influence of the shape of a dual micropipette on the collection efficiency, such as curvature and symmetry of the pipette, as well as the thickness of glassy band between generator and collector, is presented and discussed in detail. Moreover, the simulation results have been tested using the experiments of potassium and sodium ions transfers facilitated by dibenzo-18-crown-6 (DB18C6) at the water/1,2-dichloroethane (W/DCE) interface. These results demonstrate that the BE method is an efficient and useful approach for the simulation of collection efficiency of symmetric geometries of dual micropipettes operating in the G/C mode under transport conditions of diffusion control. However, there are still some problems for the cases of asymmetric dual micropipettes, which show rather large differences between the values of simulated and experimental ones. This work also indicates that such an ionic G/C technique should have advantages in applications when the dual pipettes have symmetric geometries.
基金Project (No VENI 08120) supported by the Dutch National Scientific Foundation NWO and Dutch Technology Foundation STW
文摘Dislocation dynamics simulations are performed to investigate the effect of template shape on the nanoimprinting of metal layers. To this end, metal thin films are imprinted by a rigid template made of an array of equispaced indenters of various shapes, i.e., rectangular, wedge, and circular. The geometry of the indenters is chosen such that the contact area is approximately the same at the final imprinting depth. Results show that, for all template shapes, the final patterns strongly depend on the dislocation activity, and that each imprint differs from the neighboring ones. Large material pile ups appear between the imprints, such that polishing of the metal layer is suggested for application of the patterns in electronics. Rectangular indenters require the lowest imprinting force and achieve the deepest retained imprints.
