6,827 research outputs found

    From integrated to expedient: an adaptive framework for river basin management in developing countries

    Get PDF
    Water resource management / River basin management / Water allocation / Case studies / Africa South of Sahara / Great Ruaha River Basin

    Use of a hydrological model for environmental management of the Usangu Wetlands, Tanzania

    Get PDF
    Wetlands / Rivers / Ecology / Environmental effects / Remote sensing / Hydrology / Simulation models / Water budget / Irrigated sites / Land cover / Time series analysis / Tanzania / Usangu Wetlands / Great Ruaha River

    Pinning/depinning of crack fronts in heterogeneous materials

    Full text link
    The fatigue fracture surfaces of a metallic alloy, and the stress corrosion fracture surfaces of glass are investigated as a function of crack velocity. It is shown that in both cases, there are two fracture regimes, which have a well defined self-affine signature. At high enough length scales, the universal roughness index 0.78 is recovered. At smaller length scales, the roughness exponent is close to 0.50. The crossover length ξc\xi_c separating these two regimes strongly depends on the material, and exhibits a power-law decrease with the measured crack velocity ξcvϕ\xi_c \propto v^{-\phi}, with ϕ1\phi \simeq 1. The exponents ν\nu and β\beta characterising the dependence of ξc\xi_c and vv upon the pulling force are shown to be close to ν2\nu \simeq 2 and β2\beta \simeq 2.Comment: 4 pages, latex, and 4 encapsulated postscript figure

    Wind-US Code Physical Modeling Improvements to Complement Hypersonic Testing and Evaluation

    Get PDF
    This report gives an overview of physical modeling enhancements to the Wind-US flow solver which were made to improve the capabilities for simulation of hypersonic flows and the reliability of computations to complement hypersonic testing. The improvements include advanced turbulence models, a bypass transition model, a conjugate (or closely coupled to vehicle structure) conduction-convection heat transfer capability, and an upgraded high-speed combustion solver. A Mach 5 shock-wave boundary layer interaction problem is used to investigate the benefits of k- s and k-w based explicit algebraic stress turbulence models relative to linear two-equation models. The bypass transition model is validated using data from experiments for incompressible boundary layers and a Mach 7.9 cone flow. The conjugate heat transfer method is validated for a test case involving reacting H2-O2 rocket exhaust over cooled calorimeter panels. A dual-mode scramjet configuration is investigated using both a simplified 1-step kinetics mechanism and an 8-step mechanism. Additionally, variations in the turbulent Prandtl and Schmidt numbers are considered for this scramjet configuration