An experimental investigation associated with the basic fluid mechanics in an axial flow fan is described in this paper. The flow field in the tip region has been studied by laser Doppler anemometer (LDA) and flow vis...An experimental investigation associated with the basic fluid mechanics in an axial flow fan is described in this paper. The flow field in the tip region has been studied by laser Doppler anemometer (LDA) and flow visualization technique. Some experimental data and images are interpreted to understand the complex interactions between the annulus wall boundary layer and the leakage flow. It shows that the vortex inside the blade passage is produced by the separation of annulus wall boundary layer rather than the rolling up of leakage flow.展开更多
The electric field integral equation (EFIE) combined with the multilevel fast multipole algorithm (MLFMA) is applied to analyze the radiation and impedance properties of wire antennas mounted on complex conducting pla...The electric field integral equation (EFIE) combined with the multilevel fast multipole algorithm (MLFMA) is applied to analyze the radiation and impedance properties of wire antennas mounted on complex conducting platforms to realize fast, accurate solutions. Wire, surface and junction basis functions are used to model the current distribution on the object. Application of MLFMA reduces memory requirement and computing time compared to conventional methods, such as method of moment (MOM), especially for the antenna on a large-sized platform. Generalized minimal residual (GMRES) solver with incomplete LU factorization preconditioner using a dual dropping strategy (ILUT) is applied to reduce the iterative number. Several typical numerical examples are presented to validate this algorithm and show the accuracy and computational efficiency.展开更多
Mathematical model for the pulsatile blood flow through a porous medium under the influence of periodic body acceleration for gravity flow along an inclined tube by considering blood as a couple stress, incompressible...Mathematical model for the pulsatile blood flow through a porous medium under the influence of periodic body acceleration for gravity flow along an inclined tube by considering blood as a couple stress, incompressible and electrically conducting fluid in the presence of magnetic field has been investigated. Analytical expressions for axial velocity, flow rate, fluid acceleration and shear stress are obtained by applying the Laplace and finite Hankel＇s transforms. The velocity profiles for various values of Hartmann number, couple stress parameters and the angle of inclination are shown graphically. Also the effects of body acceleration, Womerseley parameters and permeability parameters have been discussed. The results obtained in the present mathematical model for different values of the parameters involved in the problem show that the flow of blood is influenced by the effect of magnetic field, the porous medium and the inclination angle. The present model is compared with the other existing models. Through this theoretical investigation, the applications of magnetic field have also been indicated in the field of biological, biomedical and engineering sciences.展开更多
With the multi-phase field model, the unidirectional solidification with constant velocity growth and variable velocity growth of the CBr4-C2C16 eutectic alloy is simulated in three dimensions. The simulated results w...With the multi-phase field model, the unidirectional solidification with constant velocity growth and variable velocity growth of the CBr4-C2C16 eutectic alloy is simulated in three dimensions. The simulated results with constant velocity growth show that with the increase of pulling velocity, the morphology of the CBr4-C2C16 alloy evolves in the sequence of lamellar merging -lamellar-rod transition-stable lamellar growth-oscillating growth-lamellar branching. A morphology selection map is established with different pulling velocities, which is confirmed to be correct by the velocity change process. It is shown that all of the morphology transitions, the average interface growth velocity and average interface undercooling show a hysteresis effect against the instant of velocity change. The relationship between the interface average undercooling and interface average growth velocity is consistent with the theoretical value.展开更多
文摘An experimental investigation associated with the basic fluid mechanics in an axial flow fan is described in this paper. The flow field in the tip region has been studied by laser Doppler anemometer (LDA) and flow visualization technique. Some experimental data and images are interpreted to understand the complex interactions between the annulus wall boundary layer and the leakage flow. It shows that the vortex inside the blade passage is produced by the separation of annulus wall boundary layer rather than the rolling up of leakage flow.
基金This project was supported by the National Natural Science Foundation of China (60431010).
文摘The electric field integral equation (EFIE) combined with the multilevel fast multipole algorithm (MLFMA) is applied to analyze the radiation and impedance properties of wire antennas mounted on complex conducting platforms to realize fast, accurate solutions. Wire, surface and junction basis functions are used to model the current distribution on the object. Application of MLFMA reduces memory requirement and computing time compared to conventional methods, such as method of moment (MOM), especially for the antenna on a large-sized platform. Generalized minimal residual (GMRES) solver with incomplete LU factorization preconditioner using a dual dropping strategy (ILUT) is applied to reduce the iterative number. Several typical numerical examples are presented to validate this algorithm and show the accuracy and computational efficiency.
文摘Mathematical model for the pulsatile blood flow through a porous medium under the influence of periodic body acceleration for gravity flow along an inclined tube by considering blood as a couple stress, incompressible and electrically conducting fluid in the presence of magnetic field has been investigated. Analytical expressions for axial velocity, flow rate, fluid acceleration and shear stress are obtained by applying the Laplace and finite Hankel＇s transforms. The velocity profiles for various values of Hartmann number, couple stress parameters and the angle of inclination are shown graphically. Also the effects of body acceleration, Womerseley parameters and permeability parameters have been discussed. The results obtained in the present mathematical model for different values of the parameters involved in the problem show that the flow of blood is influenced by the effect of magnetic field, the porous medium and the inclination angle. The present model is compared with the other existing models. Through this theoretical investigation, the applications of magnetic field have also been indicated in the field of biological, biomedical and engineering sciences.
基金supported by the National Natural Science Foundation of China (Grant No. 51001082)the China Postdoctoral Science Foundation (Grant No. 20090460654)Shanghai Science and Technology Commit-tee (Grant Nos. 0752nm004 and 08DZ2201300)
文摘With the multi-phase field model, the unidirectional solidification with constant velocity growth and variable velocity growth of the CBr4-C2C16 eutectic alloy is simulated in three dimensions. The simulated results with constant velocity growth show that with the increase of pulling velocity, the morphology of the CBr4-C2C16 alloy evolves in the sequence of lamellar merging -lamellar-rod transition-stable lamellar growth-oscillating growth-lamellar branching. A morphology selection map is established with different pulling velocities, which is confirmed to be correct by the velocity change process. It is shown that all of the morphology transitions, the average interface growth velocity and average interface undercooling show a hysteresis effect against the instant of velocity change. The relationship between the interface average undercooling and interface average growth velocity is consistent with the theoretical value.
