The pre-launch Planck Sky Model: a model of sky emission at submillimetre to centimetre wavelengths

We present the Planck Sky Model (PSM), a parametric model for the generation of all-sky, few arcminute resolution maps of sky emission at submillimetre to centimetre wavelengths, in both intensity and polarisation. Several options are implemented to model the cosmic microwave background, Galactic diffuse emission (synchrotron, free-free, thermal and spinning dust, CO lines), Galactic H-II regions, extragalactic radio sources, dusty galaxies, and thermal and kinetic Sunyaev-Zeldovich signals from clusters of galaxies. Each component is simulated by means of educated interpolations/extrapolations of data sets available at the time of the launch of the Planck mission, complemented by state-of-the-art models of the emission. Distinctive features of the simulations are: spatially varying spectral properties of synchrotron and dust; different spectral parameters for each point source; modeling of the clustering properties of extragalactic sources and of the power spectrum of fluctuations in the cosmic infrared background. The PSM enables the production of random realizations of the sky emission, constrained to match observational data within their uncertainties, and is implemented in a software package that is regularly updated with incoming information from observations. The model is expected to serve as a useful tool for optimizing planned microwave and sub-millimetre surveys and to test data processing and analysis pipelines. It is, in particular, used for the development and validation of data analysis pipelines within the planck collaboration. A version of the software that can be used for simulating the observations for a variety of experiments is made available on a dedicated website.Comment: 35 pages, 31 figure

Velocity Measurements within High Velocity Air-Water Jets

High velocity turbulent jets are often used in hydraulic structures to dissipate energy and to induce or enhance air entrainment. Examples include ski jumps and bottom aeration devices. This article presents new air concentration and velocity measurements performed in the flow development region of high velocity water jets. The measurements were obtained using a two-tips conductivity probe. The data are compared with analytical air concentration profiles derived from the diffusion equation, and theoretical velocity profiles of turbulent shear layers. The results highlight that the lower jet interface defined as C = 90% coincides with the streamline of maximum velocity gradient

Étude statistique de la dispersion d’un jet de turbine Pelton

A statistical study of the dispersion of a Pelton jet. The statistical interpretation of a number of series of high-speed photographs taken at only a few micro-seconds exposure provides a means of determining the mean jet diameter for each cross-sectional area of a given jet exactly. This method is used for a systematic study of the dispersion of a jet issuing from a given nozzle. The diameters of the contracted sections vary between 15 and 35 mm, for jet velocities of approximately 15 to 40 m/s.Le dépouillement statistique de séries de photographies à très court temps de pose (quelques microsecondes) permet pour chaque section d'un jet donné, de déterminer exactement la valeur moyenne du diamètre du jet. Ce procédé est exploité pour étudier systématiquement la dispersion d'un jet issu d'un injecteur donné. Les diamètres des sections contractées varient de 15 à 35 mm et les vitesses des jets de 15 à 40 m/s environ.Dodu J. Étude statistique de la dispersion d’un jet de turbine Pelton. In: Turbines et pompes hydrauliques. Compte rendu des cinquièmes journées de l'hydraulique, Aix-en-Provence, 26, 27 et 28 juin 1958. Tome 1, 1959