Investigations of Fluid-Structure-Coupling and Turbulence Model Effects on the DLR Results of the Fifth AIAA CFD Drag Prediction Workshop

images[7]The accurate calculation of aerodynamic forces and moments is of significant importance during the design phase of an aircraft. Reynolds-averaged Navier-Stokes (RANS) based Computational Fluid Dynamics (CFD) has been strongly developed over the last two decades regarding robustness, efficiency, and capabilities for aerodynamically complex configurations. Incremental aerodynamic coefficients of different designs can be calculated with an acceptable reliability at the cruise design point of transonic aircraft for non-separated flows. But regarding absolute values as well as increments at off-design significant challenges still exist to compute aerodynamic data and the underlying flow physics with the accuracy required. In addition to drag, pitching moments are difficult to predict because small deviations of the pressure distributions, e.g. due to neglecting wing bending and twisting caused by the aerodynamic loads can result in large discrepancies compared to experimental data. Flow separations that start to develop at off-design conditions, e.g. in corner-flows, at trailing edges, or shock induced, can have a strong impact on the predictions of aerodynamic coefficients too. Based on these challenges faced by the CFD community a working group of the AIAA Applied Aerodynamics Technical Committee initiated in 2001 the CFD Drag Prediction Workshop (DPW) series resulting in five international workshops. The results of the participants and the committee are summarized in more than 120 papers. The latest, fifth workshop took place in June 2012 in conjunction with the 30th AIAA Applied Aerodynamics Conference. The results in this paper will evaluate the influence of static aeroelastic wing deformations onto pressure distributions and overall aerodynamic coefficients based on the NASA finite element structural model and the common grids. Personal Author B. Eisfeld M. B. Rivers O. P. Brodersen S. Keye V. Togiti
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Managing Critical Isotopes: Stewardship of Lithium-7 Is Needed to Ensure a Stable Supply

images[4]About 13 percent of our nation’s electricity is produced by pressurized water reactors that rely on lithium-7, an isotope of lithium produced and exported solely by China and Russia, for their safe operation. Lithium-7 is added to the water that cools the reactor core to prevent the cooling water from becoming acidic. Without the lithium-7, the cooling waters acidity would increase the rate of corrosion of pipes and other infrastructure possibly causing them to fail. Utilities that operate the pressurized water reactors have experienced little difficulty obtaining lithium-7, but they may not be aware of all the risks of relying on two producers. GAO was asked to review the supply and domestic demand for lithium-7 and how risks are being managed. This report examines (1) what is known about the supply and demand of lithium-7, (2) what federal agencies are responsible for managing supply risks, and (3) alternative options to mitigate a potential shortage. GAO reviewed documents and interviewed officials from DOE, NNSA, and NRC, in addition to industry representatives. This report is an unclassified version of a classified report also issued in September 2013. For more info please go
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