Dynamics and decay of spatially-evolving two- and four-vortex wakes near the ground

The purpose of the Task 3.1 was to investigate the dynamics and decay of wake vortices near the ground in idealized and controlled computational and laboratory conditions (i.e wake vortices released over a flat ground, without wind or turbulence). The outcome of this task, together with Task 3.2, also served as input to Task 3.3 which concerns the improvement of real-time operational models. This task was divided in two main subtasks. The first subtask (3.1.1) con- cerns longitudinally uniform wakes (time developing wakes) while the second one (3.1.2) concerns spatially evolving wakes. The present deliverable reports on the second subtask. It is made of four detailed technical reports (annexed). We here only summarize the main outcomes (executive summary)

Soil moisture monitoring over wetland areas using GNSS signals

International audienceDuring summer 2015, two experimental campaigns in the framework of the Mistrale Project have been carried. In those campaigns a complete GNSS-R sensor was installed on an ultralight aircraft, allowing gathering polarimetric GNSS-R data. The flights were done in France over the Camargue area (flooded areas, marshlands and water salinity changes), and Pech Rouge area (agricultural plots).The estimated reflection coefficients acquired during the flights, have been computed and geo-referenced on ground, showing that the reflection coefficients are sensible to terrain changes. Main results are presented in this work

Geo-distributed simulation and verification infrastructure for safe train galileo-based positioning

The work shows the high level concept and methodology followed for designing a geo-distributed simulation and verification infrastructure connecting remotely GNSS excellence centres and ERTMS/ETCS laboratories to evaluate the GNSS performances in the railway environment. Proper methodology and tools are adopted to simulate GNSS behaviour in different railway scenarios in nominal or in presence of global and local hazards. Particularly, the test-bed main goals are: i) achieving a realistic characterization of the environment in terms of railway and GNSS infrastructures able to evaluate the performances and properties of some fail-safe train positioning components in nominal and fault conditions; ii) defining a common test process framework for zero on-site testing instead of testing on-site saving effort and time. The test-bed offers the unique advantage to stress the global system in presence of very rare GNSS fault events instead of performing long and expensive measurement campaigns on field for detecting them and analysing their impact on ETCS. The work will show its description and the methodology adopted for its design and implementation

Direct Numerical Simulation and Large-Eddy Simulation of wake vortices: Going from laboratory conditions to flight conditions

This paper aims at presenting DNS and LES as applied to the simulation of vortex wakes: in laboratory conditions (moderate to medium Reynolds numbers) and up to real aircraft conditions (high to very high Reynolds numbers). Only incompressible flows are considered. DNS and LES are able to capture complex 3-D physics provided one uses high quality numerical methods: methods with negligible numerical dissipation (i.e., methods that conserve energy in absence of viscosity and/or subgrid modelling) and with low dispersion errors (to properly transport complex vortical structures). Methods that can do that are: spectral methods, high order finite difference methods, and vortex-in-cell (VIC) methods. As the problems of interest are of large spatial extent and contain vortices with small cores, it is also essential that the methods be efficiently parallelized. As to LES of wake vortex flows, this require subgrid scale (SGS) models that are essentially inactive during the gentle, well-resolved, phases of the flow and within the vortex cores, and that become active only during the complex turbulent phases of the flow. The recent multiscale models, that act solely on the high wavenumbers modes of the LES, are seen to be most appropriate. We present some illustrative examples of DNS and LES results that were obtained within our group