BEGIN:VCALENDAR VERSION:2.0 PRODID:-//wp-events-plugin.com//7.2.3.1//EN TZID:Europe/Paris X-WR-TIMEZONE:Europe/Paris BEGIN:VEVENT UID:7731@i2m.univ-amu.fr DTSTART;TZID=Europe/Paris:20161014T140000 DTEND;TZID=Europe/Paris:20161014T153000 DTSTAMP:20241120T204815Z URL:https://www.i2m.univ-amu.fr/evenements/3-exposes-de-30min-donnes-par-k -schneider-i2m-s-gomes-unicamp-et-f-jacobitz-u-san-diego/ SUMMARY: (...): 3 exposés de 30min donnés par K. Schneider (I2M)\, S. Gom es (Unicamp) et F. Jacobitz (U. San Diego) DESCRIPTION:: Nous aurons le plaisir d'écouter {{3 exposés de 30min}} don nés par :- K. Schneider (I2M) - Tomographic reconstruction using wavelet- vaguelette decomposition for inverting the helical Abel transform. Applica tion to tokamak edge turbulence light emission from a single image.- S. Go mes (Unicamp) - Multiresolution and adaptive mesh refinement schemes for E uler equations: a comparative study- F. Jacobitz (U. San Diego) - On Multi scale Acceleration Statistics in Rotating and Sheared Homogeneous Turbulen ce-Organisateurs : Caroline Chaux (I2M) et François-Xavier Dupé (LIF)--- -------------------------------------------------------------------------- ------------------------------------------------Title: Tomographic reconst ruction using wavelet-vaguelette decomposition for inverting the helical A bel transform. Application to tokamak edge turbulence light emission from a single image.{{Kai Schneider}}\, I2M\, AMU-Images acquired by cameras in stalled in tokamaks are difficult to interpret because the three-dimension al structure of the plasma is flattened in a non-trivial way. Nevertheless \, taking advantage of the slow variation of the fluctuations along magnet ic field lines\, the optical transformation may be approximated by a gener alized Abel transform\, for which we propose an inversion technique based on the wavelet-vaguelette decomposition. After validation of the new metho d using an academic test case and numerical data obtained with the Tokam 2 D code\, we present an application to an experimental movie obtained in th e tokamak Tore Supra. A comparison with a classical regularization techniq ue for ill-posed inverse problems\, the singular value decomposition\, all ows us to assess the efficiency. The superiority of the wavelet-vaguelette technique is reflected in preserving local features\, such as blobs and f ronts\, in the denoised emissivity map.-Ref.: R. Nguyen van yen\, N. Fedor czak\, F. Brochard\, G. Bonhomme\, K. Schneider\, M. Farge and P. Monier-G arbet. Tomographic reconstruction of tokamak edge turbulence light emissio n from a single image using wavelet-vaguelette decomposition. Nucl. Fusion \, 52\, 013005\, 2012.---------------------------------------------------- --------------------------------------------------------------Title: Multi resolution and adaptive mesh refinement schemes for Euler equations: a com parative study.{{Sonia Gomes}}\, Professor\, Unicamp\, Campinas\, Brazil\, currently visiting IHP.-We present some comparison results between two ad aptive numerical methods\, namely the adaptive multiresolution method and the adaptive mesh refinement method for the resolution of 2D and 3D compre ssible Euler equations. The results are compared with respect to accuracy and computational efficiency\, in terms of CPU time and memory requirement s\, with the corresponding finite volume scheme on a regular fine grid. Fo r both methods\, we use second-order schock-capturing schemes for the spac e discretization\, together with explicit second-order Runge-Kutta time in tegration.-Ref.: R. Deiterding\, M. Domingues\, S. Gomes and K. Schneider. Comparison of adaptive multiresolution and adaptive mesh refinement appli ed to simulations of the compressible Euler equations. SIAM J. Sci. Comput .\, 03/2016\, arXiv:1603.05211\, accepted.-------------------------------- -------------------------------------------------------------------------- ---------Title: On Multiscale Acceleration Statistics in Rotating and Shea red Homogeneous Turbulence.{{Frank Jacobitz}}\, Professor\, U. San Diego\, USA\, currently visiting I2M-The acceleration statistics of sheared and r otating homogeneous turbulence are studied using direct numerical simulati on results with different rotation ratios of Coriolis parameter to shear r ate $f/S$. For the range of rotation ratios $0 \\le f/S \\le 1$\, a destab ilization of the flow due to rotation and growth of the turbulent kinetic energy is obtained. For other values of $f/S$\, rotation stabilizes the fl ow and a decay of the turbulent kinetic energy is observed. The statistica l properties of Lagrangian and Eulerian acceleration are considered and th e influence of the rotation ratio and the scale dependence of the statisti cs is investigated. The probability density functions (pdfs) of both Lagra ngian and Eulerian acceleration show a strong and similar dependence on th e rotation ratio. The flatness further quantifies its dependence and yield s values close to three for strong rotation. For moderate and vanishing ro tation\, the flatness of the Eulerian acceleration is larger than that of the Lagrangian acceleration\, contrary to previous results for isotropic t urbulence. A wavelet-based scale-dependent analysis shows that the flatnes s of both Eulerian and Lagrangian acceleration increases as scale decrease s. For strong rotation\, the Eulerian acceleration is more intermittent th an the Lagrangian acceleration\, while the opposite result is obtained for moderate rotation.-Ref.: F.G. Jacobitz\, K. Schneider\, W.J.T. Bos and M. Farge. Structure of sheared and rotating turbulence: Multiscale statistic s of Lagrangian and Eulerian accelerations and passive scalar dynamics. Ph ys. Rev. E\, 93\, 013113\, 2016.------------------------------------------ ------------------------------------------------------------------------- END:VEVENT BEGIN:VTIMEZONE TZID:Europe/Paris X-LIC-LOCATION:Europe/Paris BEGIN:DAYLIGHT DTSTART:20160327T030000 TZOFFSETFROM:+0100 TZOFFSETTO:+0200 TZNAME:CEST END:DAYLIGHT END:VTIMEZONE END:VCALENDAR