Papers by Keyword: Aerodynamics Force

Abstract: Theoretical three-dimensional Gaussian heat distribution model of the complex heat flow and plasma properties of cutting plasma torches have been developed. For cutting metallic plates, plasma torches must produce a narrow supersonic plasma jet with enough energy and momentum densities to melt, vaporize, and remove the metal from the impingement region. Our model allows us to study the details of the heat distribution and to make predictions on pick temperature development on metal surface, heat transfer to the work piece, force i.e. the forces acting on the melt (aerodynamic drag, gravity, viscosity and surface tension) during plasma arc cutting, the main forces acting on the melt is believed to be the aerodynamic drag force and the gravity is significant only for thick metal plates. With the help of these assumptions and diameter of Gaussian heat source’s volume, diameter of nozzle has been calculated for thin work piece. A good agreement is found between the model results and the available experimental data.

Abstract: As the speed of train increases, flow-induced vibration of trains passing through tunnels has become a subject of discussion, to investigate this phenomenon, a simplified geometric model and a vehicle dynamics model of a high-speed train traveling through a tunnel were built. To analyze the unsteady three-dimensional flow around the train, the 3-D, transient, viscous, compressible Reynolds-averaged Navier-Stokes equations combined with the k- two-equation turbulence model were solved with the finite volume method. The motion of the train was carried out using the technique of sliding grid method. The dynamics response of the train was obtained by means of the computational multi-body dynamics calculation. Meanwhile the running safety and riding comfort of the train were analyzed. With the numerical simulation, the variation of aerodynamic forces was obtained. The research founds that, vibration of the train increases drastically during it passing through a tunnel. The running safety and riding quality of the train are reduced greatly but they are in the safe range.