Extreme Energy Cosmic Rays (EECR) Observation Capabilities of an "Airwatch from Space'' Mission

The longitudinal development and other characteristics of the EECR induced atmospheric showers can be studied from space by detecting the fluorescence light induced in the atmospheric nitrogen. According to the Airwatch concept a single fast detector can be used for measuring both intensity and time development of the streak of fluorescence light produced by the atmospheric shower induced by an EECR. In the present communication the detection capabilities for the EECR observation from space are discussed.Comment: 3 pages (LaTeX). To appear in the Proceedings of TAUP'9

UV and EUV Instruments

We describe telescopes and instruments that were developed and used for astronomical research in the ultraviolet (UV) and extreme ultraviolet (EUV) regions of the electromagnetic spectrum. The wavelength ranges covered by these bands are not uniquely defined. We use the following convention here: The EUV and UV span the regions ~100-912 and 912-3000 Angstroem respectively. The limitation between both ranges is a natural choice, because the hydrogen Lyman absorption edge is located at 912 Angstroem. At smaller wavelengths, astronomical sources are strongly absorbed by the interstellar medium. It also marks a technical limit, because telescopes and instruments are of different design. In the EUV range, the technology is strongly related to that utilized in X-ray astronomy, while in the UV range the instruments in many cases have their roots in optical astronomy. We will, therefore, describe the UV and EUV instruments in appropriate conciseness and refer to the respective chapters of this volume for more technical details.Comment: To appear in: Landolt-Boernstein, New Series VI/4A, Astronomy, Astrophysics, and Cosmology; Instruments and Methods, ed. J.E. Truemper, Springer-Verlag, Berlin, 201

Numerical study of turbulent heat transfer above a porous wall

This paper presents a numerical study of fully developed turbulent heat transfer in a flat channel half filled with porous material; the simulated fluid is air while an aluminium foam represents the solid matrix. The main focus is on heat transfer performances of a porous wall, the interface between a saturated porous medium and the clear fluid, in forced convection conditions; in the fluid portion a turbulent regime with a Reynolds number based on the mean velocity and the hydraulic diameter Re=9000 is sustained. The Nusselt number and the efficiency computed on the porous wall is sensibly higher than the flat wall value and this is in direct relation with the presence of a higher peak of the wall-normal turbulent heat flux

Comet Hale-Bopp (C/1995 O1): UVSTAR-FUV Spectroscopy from the Shuttle

Es wird die Entdeckung von N2 in den UV-Spektren des Kometen Hale-Bopp beschrieben und die Wasserproduktionsrate hergeleitet. Ein Nachweis von Argon ist schwierig, das Signal-/Rauschverhältnis nicht genügend groß ist

Reference numerical database for turbulent flow and heat transfer in liquid metals

Turbulent heat transfer is a complex phenomenon that has challenged turbulence modellers over various decades. In this regard, in the recent past, several attempts have been made for the assessment and further development/calibration of the available turbulent heat flux modelling approaches. One of the main hampering factors with respect to the further assessment of these modelling approaches is the lack of reference data. In the framework of the EU SESAME and MYRTE projects, an extensive effort has been put forward to generate a wide range of reference data, both experimental and numerical, to fill this gap. In that context, this article reports the numerical database that has been generated within these projects for various liquid metal flow configurations in different flow regimes. These high fidelity numerical data include seven different flow configurations: a wall-bounded mixed convection flow at low Prandtl number with varying Richardson number (Ri) values; a wall-bounded mixed and forced convection flow in a bare rod bundle configuration; a forced convection confined backward facing step (BFS) with conjugate heat transfer; a forced convection impinging jet for three different Prandtl fluids corresponding to two different Reynolds numbers of the fully developed planar turbulent jets; a mixed-convection cold-hot-cold triple jet configuration corresponding to Ri=0.25; an unconfined free shear layer for three different Prandtl fluids; and a forced convection infinite wire-wrapped fuel assembly. These high-fidelity numerical databases will serve the further development of turbulent heat transfer models by providing unique, new and detailed data for the thermal-hydraulic behaviour of liquid metals in various flow configurations

European Developments in SIngle Phase Turbulence for Innovative Reactors

Thermal-hydraulics is recognized as a key (safety) challenge in the development of innovative nuclear reactor systems. Different innovative reactors are mainly characterized by their coolants from a thermal-hydraulic point of view. They result in different behavior of flow and heat transfer and require specific models and advanced analysis tools. However, many common thermal-hydraulic challenges are identified among various innovative nuclear systems. In Europe, such challenges are the subject of the THINS (Thermal-Hydraulics of Innovative Nuclear Systems) project which is sponsored by the European Commission from 2010 to 2014. This paper describes the ongoing developments in an important part of this project which is devoted to single phase turbulence issues. To this respect, two main issues have been identified: • Non-unity Prandtl number turbulence. In cases of liquid metals, molten salts or supercritical fluids, the commonly applied turbulent Prandtl number concept is not applicable and robust engineering turbulence models are needed. This paper will report about the experiments and direct numerical simulations which have been performed in support of validating improved turbulence models. Furthermore, this paper demonstrates the progress achieved in the development and validation of Reynolds Averaged Navier Stokes (RANS) and Large Eddy Simulation (LES) turbulence models. With respect to improved RANS models, carefully selected promising algebraic heat flux models have been implemented and evaluated which should lead to improved numerical modeling of non-unity Prandtl number flows. • Temperature fluctuations possibly leading to thermal fatigue in innovative reactors. A basic mixing experiment will be described of different density gases in a rectangular channel together with numerical model developments, support and validation. Secondly, the preparation of an experiment in a more complex geometry of a small mixing plenum using a supercritical fluid is described including the numerical support. And finally, direct numerical simulations of conjugate heat transfer on temperature fluctuations in liquid metal will be reported together with validation of LES models

A collaborative effort towards the accurate prediction of turbulent flow and heat transfer in low-Prandtl number fluids

This article reports the experimental and DNS database that has been generated, within the framework of the EU SESAME and MYRTE projects, for various low-Prandtl flow configurations in different flow regimes. This includes three experiments: confined and unconfined backward facing steps with low-Prandtl fluids, and a forced convection planar jet case with two different Prandtl fluids. In terms of numerical data, seven different flow configurations are considered: a wall-bounded mixed convection flow at low-Prandtl number with varying Richardson number (Ri) values; a wall-bounded mixed and forced convection flow in a bare rod bundle configuration for two different Reynolds numbers; a forced convection confined backward facing step (BFS) with conjugate heat transfer; a forced convection impinging jet for three different Prandtl fluids corresponding to two different Reynolds numbers of the fully developed planar turbulent jet; a mixed-convection cold-hot-cold triple jet configuration corresponding to Ri=0.25; an unconfined free shear layer for three different Prandtl fluids; and a forced convection infinite wire-wrapped fuel assembly. This wide range of reference data is used to evaluate, validate and/or further develop different turbulent heat flux modelling approaches, namely simple gradient diffusion hypothesis based on constant and variable turbulent Prandtl number; explicit and implicit algebraic heat flux models; and a second order turbulent heat flux model. Lastly, this article will highlight the current challenges and perspectives of the available turbulence models, in different codes, for the accurate prediction of flow and heat transfer in low-Prandtl fluids. © 2019 American Nuclear Society. All rights reserved