The flow characteristics of a 2D slot jet vertically impinging on free surfaces are numerically investigated by the Large Eddy Simulation （LES） with a dynamic Sub-Grid Scale （SGS） model. The σ-coordinate transfor...The flow characteristics of a 2D slot jet vertically impinging on free surfaces are numerically investigated by the Large Eddy Simulation （LES） with a dynamic Sub-Grid Scale （SGS） model. The σ-coordinate transformation is introduced to map the depth-variable physical domain to a depth-uniform computational domain. The split-operator scheme, which splits the solution procedure into advection, diffusion and pressure propagation steps, is employed to solve the instantaneous velocity and pressure field. A fully nonlinear Lagrange-Euler method is used to compute the free surface elevation. The numerical results show that the jet retains good self-similarity in the Zone of Eestablished Flow （ZEF）, while the turbulence of jet shifts gradually from isotropic to anisotropic in the Zone of Surface Impingement （ZSI）. When the jet approaches the free surface, the centerline velocity decreases rapidly and the flow is deflected by the free surface. Two symmetrical surface jets are formed in the Zone of Horizontal Jets （ZHJ）. An approximate Guassian distribution of super-elevation is also formed on the free surface. The computed results are in good agreement with the available experimental data.展开更多
Considering the shortcomings of the existing vehicle-to-vehicle（V2V） communication antennas, this paper proposes a regular hexagon broadband microstrip antenna. By loading shorting pins and etching V-shape slots wit...Considering the shortcomings of the existing vehicle-to-vehicle（V2V） communication antennas, this paper proposes a regular hexagon broadband microstrip antenna. By loading shorting pins and etching V-shape slots with different size at each angle of the regular hexagon patch, it realizes impedance matching and obtains better impedance bandwidth. The simulated results show that the relative bandwidth of this antenna reaches 35.55%, covers the frequency band of 4.74 GHz to 6.79 GHz. The antenna acquires an omni-directional radiation pattern in the horizontal plane whose out of roundness is less than 0.5 d B. In addition, the antenna is manufactured and tested, whose tested results are basically consistent with simulated results. Because the height of antenna is 3 mm, it is easy to be hidden on roof of a vehicle for V2 V communication.展开更多
基金Project supported by a grant from the Research Grant Council of the Hong Kong Special Administrative Region (Grant No: 5048/01E).
文摘The flow characteristics of a 2D slot jet vertically impinging on free surfaces are numerically investigated by the Large Eddy Simulation （LES） with a dynamic Sub-Grid Scale （SGS） model. The σ-coordinate transformation is introduced to map the depth-variable physical domain to a depth-uniform computational domain. The split-operator scheme, which splits the solution procedure into advection, diffusion and pressure propagation steps, is employed to solve the instantaneous velocity and pressure field. A fully nonlinear Lagrange-Euler method is used to compute the free surface elevation. The numerical results show that the jet retains good self-similarity in the Zone of Eestablished Flow （ZEF）, while the turbulence of jet shifts gradually from isotropic to anisotropic in the Zone of Surface Impingement （ZSI）. When the jet approaches the free surface, the centerline velocity decreases rapidly and the flow is deflected by the free surface. Two symmetrical surface jets are formed in the Zone of Horizontal Jets （ZHJ）. An approximate Guassian distribution of super-elevation is also formed on the free surface. The computed results are in good agreement with the available experimental data.
基金supported by the Science and Technology Research Project of Chongqing Municipal Education Commission(KJ1400417,KJ130531)
文摘Considering the shortcomings of the existing vehicle-to-vehicle（V2V） communication antennas, this paper proposes a regular hexagon broadband microstrip antenna. By loading shorting pins and etching V-shape slots with different size at each angle of the regular hexagon patch, it realizes impedance matching and obtains better impedance bandwidth. The simulated results show that the relative bandwidth of this antenna reaches 35.55%, covers the frequency band of 4.74 GHz to 6.79 GHz. The antenna acquires an omni-directional radiation pattern in the horizontal plane whose out of roundness is less than 0.5 d B. In addition, the antenna is manufactured and tested, whose tested results are basically consistent with simulated results. Because the height of antenna is 3 mm, it is easy to be hidden on roof of a vehicle for V2 V communication.
