Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 16 of 16 for “"Roughness length"”.
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Roughness length variability over heterogeneous surfaces
… al. (1971) and Dyer (1974) are used to calculate roughness lengths and surfacelayer heat fluxes from multilevel observations of wind, temperature, and humidity measured at three locations in the Weather Information Network Display System at Cape Canaveral Air Force Station, Florida. Relationships …
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An investigation of momentum exchange parameterizations and atmospheric forcing for the Coastal Mixing and Optics Program
… incorporating sea state dependence into the roughness length calculation. For the inertial dissipation method, a new parameterization for the dimensionless dissipation rate is proposed. The modifications lead to improved momentum flux estimates for both methods.
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An investigation of momentum exchange parameterizations and atmospheric forcing for the Coastal Mixing and Optics Program
… incorporating sea state dependence into the roughness length calculation. For the inertial dissipation method, a new parameterization for the dimensionless dissipation rate is proposed. The modifications lead to improved momentum flux estimates for both methods.
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Exploration of a geometric approach for estimating snow surface roughness
The roughness of a surface that influences atmospheric turbulence is estimated as the aerodynamic roughness length (Z0), and is used to understand the flow of air, temperature, and moisture over a surface. Z0 is a critical variable for estimating latent and sensible fluxes at the surface, but most …
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Simple models for turbulent wave-current bottom boundary layer flow : theoretical formulations and applications
… Barreto-Acobe (2001) flow models. Bottom roughness and ripple geometry models are developed for each model using fixed bed laboratory data and movable bed laboratory and field data. Wave attenuation measurements and current profile data are used in order to investigate the bottom roughness …
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Flow and skin friction over natural rough beds
… from the isolated-element case, and the roughness length in arrays of two areal densities is not altered by addition of tails.
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Surface-Atmosphere coupling over the central Arctic Ocean
… is shown to be due to the use of a value for the roughness length for momentum, z0 that is too large and the application of Monin-Obukhov similarity theory under the observed conditions. The measurements show that the boundary layer was almost always less than 200 m deep; this means that the …
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Modeling Cumulative Damage to Flow Surfaces and Assessing its Impact on Wall Turbulence
… modes embodying successively smaller roughness length scales. These modes were then used to develop multiple reduced-order models of the original roughness that, at least in spirit, successively captured the evolution of the surface roughness from initial smaller-scale defects that …
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Advanced materials for enhanced condensation heat transfer
… governing adhesion on surfaces with multiple roughness length scales. We introduce the metric of pinned fraction to show how these surfaces must be designed to minimize adhesion. We then show how dropwise condensation on superhydrophobic surfaces and the ensuing "jumping" behavior consists of …
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Modelling bottom stress in depth-averaged flows
… is the water depth 2) the non-dimensional bottom roughness, zo/h where zo is the roughness length and 3) the angle between the wind stress and the shoreline. Each has significant influence on the drag law. The drag tensor magnitude, r, and the drag sensor angle, θ are functions of all three, while …
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Modelling bottom stress in depth-averaged flows
… is the water depth 2) the non-dimensional bottom roughness, zo/h where zo is the roughness length and 3) the angle between the wind stress and the shoreline. Each has significant influence on the drag law. The drag tensor magnitude, r, and the drag tensor angle, 0 are functions of all three, while …
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Mineral dust lofting and interactions with cold pools
… of surface type is dominated by the change in roughness length. A semi-linear connection between haboob dust and cold pool temperature is detected in the statistics, and a relationship between dust flux and cold pool temperature is proposed which relates haboob strength to the thermodynamic …
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The effects of variation in wave period and flow asymmetry in sediment dynamics
… wave periods together with relatively small bed roughness length-scales, the observed values deviate from the rough-bed relationship and tend towards the smooth-bed limiting value. Flow asymmetry acts to stabilise the boundary layer, increasing either the critical boundary Reynolds number RE 2? …
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Adoption of footprint methods for the quality control of eddy-covariance measurements
… of the land use maps and different roughness length assignment schemes on the performance of the site evaluation approach. Finally, Göckede et al. (2005a) developed an updated version of the site evaluation approach, which improved the basic method by replacing the analytic footprint …
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Analysis of the spatial heterogeneity of land surface parameters and energy flux densities
… speed, relative humidity, vegetation height and roughness length, for example. They were derived indirectly from the given satellite- or in-situ measurements. If no data were available so called default values from literature were taken. The quality of these parameters strongly influenced the …