Browsing by Subject "Rough surface"
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Item Application of dye tracing on sheet flow and determination of mean texture depth on a rough surface(2007-12) Chan, Wa Seong, 1983-; Charbeneau, Randall J.A flume surface covered with sand grains of around 2 mm diameter was created to imitate the roadway surface of a highway. Rainfall and water flow was simulated over the surface which was elevated on one side to create slopes of 1%, 2%, and 3%. Mean texture depth was proposed such that water depth has to be greater than the mean texture depth to establish significant flow on a rough surface. Two methods were used to determine the mean texture depth. The first method involved fitting discharge and depth measurements to a model equation to determine the mean texture depth which was found to exist and it varied from 2.012 to 5.651 mm in "no rain" condition and from 1.580 to 5.348 mm in "rain" condition. The second method was to measure the discharge rate using dye tracing method. However, this method proved to be less successful. The mean texture depth determined by this method was negative in some conditions. The sink effect at the water collecting slots and the error of slot width measurements were investigated as potential source of error.Item Three transdimensional factors for the conversion of 2D acoustic rough surface scattering model results for comparison with 3D scattering(2013-12) Tran, Bryant Minh; Wilson, Preston S.; Isakson, Marcia J.Rough surface scattering is a problem of interest in underwater acoustic remote sensing applications. To model this problem, a fully three-dimensional (3D) finite element model has been developed, but it requires an abundance of time and computational resources. Two-dimensional (2D) models that are much easier to compute are often employed though they don’t natively represent the physical environment. Three quantities have been developed that, when applied, allow 2D rough surface scattering models to be used to predict 3D scattering. The first factor, referred to as the spreading factor, adopted from the work of Sumedh Joshi [1], accounts for geometrical differences between equivalent 2D and 3D model environments. A second factor, referred to as the perturbative factor, is developed through the use of small perturbation theory. This factor is well-suited to account for differences in the scattered field between a 2D model and scattering from an isotropically rough 2D surface in 3D. Lastly, a third composite factor, referred to as the combined factor, of the previous two is developed by taking their minimum. This work deals only with scattering within the plane of the incident wave perpendicular to the scatterer. The applicability of these factors are tested by comparing a 2D scattering model with a fully three-dimensional Monte Carlo finite element method model for a variety of von Karman and Gaussian power spectra. The combined factor shows promise towards a robust method to adequately characterize isotropic 3D rough surfaces using 2D numerical simulations.