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Abstract: Several wireless communication systems are developed for communication needs between train and ground and between trains in the railway or mass transit domains. They are developed for operational needs for security and comfort. In order to deploy these systems in specific environments, such as tunnels, straight or curved, rectangular or arch-shaped section, specific propagation models have to be developed. A modelisation of the radio wave propagation in straight arch-shaped tunnels is realized by using asymptotic methods, such as Ray Tracing and Ray Launching, combined with the tessellation of the arched section. A method of interpolation of the facets'' normals was implemented in order to minimize the error made when using the tessellation. Results obtained are validated by comparison to the literature and to measurement results. [Copyright &y& Elsevier]

Abstract: The near-field (up to about 20 spans) development of trailing vortices is investigated experimentally and numerically. Computational Fluid Dynamics (CFD) results are based on the solution of quasi-3D Reynolds-averaged Navier–Stokes equations with a one-equation turbulence model. The inclusion of turbulence effects is found to be essential to capturing the correct near-field development. The CFD results are shown to be in very good agreement with experimental wake-survey results out to ten spans. Results show that wing loadings typical of commercial airplanes in a landing configuration can lead to multiple, or single vortex pairs, at distances of fifteen to twenty spans downstream. To cite this article: M. Czech et al., C. R. Physique 6 (2005). [Copyright &y& Elsevier]