Part I: Geostatistical Interpolation of Rain Fields Using Radar Estimates and Gauge Observations: Algorithm Design and Automation; Part II: Energy Dissipation in Fluid Flows and Wave Transformation by Porous Barriers and Submerged Cavities

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This research consists of two parts. The first part aims to improve the accuracy of rain field interpolation with the utilization of radar rainfall during extreme storm events for a study watershed. The second part studies the head loss induced by fluids passing through porous screens and the wave transformation caused by porous barriers as well as submerged cavities. In the first part of the study, the regression-kriging (RK) and merging spatial interpolation techniques were applied to predict rain fields using radar rainfall estimates as an auxiliary variable for the Chenyulan River watershed in Taiwan. Severe property damage and loss of lives are often inevitable at the times of typhoons. Reliable warning systems are of great importance to provide the emergency response agencies with vital information for early action planning. The developed algorithms were tested against univariate methods, such as the ordinary kriging, with five historical typhoon events. The results have shown that the accuracy of rainfall prediction could be significantly improved by the proposed algorithms and multivariate techniques are superior to univariate methods, especially where sampling condition is inadequate. Porous media have many practical engineering applications. Porous screens are commonly seen at the inlets of wastewater treatment plants for the removal of coarse trash. Porous barriers are generally used to reduce wave motions in coastal regions by dissipating the incoming wave energy. This part of the research emphasized on the head loss induced by fluids passing through porous screens. The effects of screen pore size, porosity, and angle of inclination were investigated experimentally, and empirical relationships which could potentially be used to predict head loss were deduced. The wave transformation caused by porous barriers was the next topic to be studied. Analytical solutions based on the linear wave theory using a potential flow approach with the adoption of Darcy’s law as a boundary condition were derived. The analytical results were validated by experimental data collected in this study. Finally, the induced vortices and fluid particle entrainment process as solitary waves propagated past a submerged cavity were studied experimentally. The PLIF technique was used to visualize the wave field and evolved vortices around the cavity zone. The maximum transporting distance of bottom fluid particles was analyzed with measured data and compared to the available numerical results.

Geostatistical interpolation, Radar rainfall adjustment, Regression-kriging, Porous media, Porous materials, Submerged cavities, PLIF, Water wave transformation, Flow head loss
Portions of this document appear in: Chang, Chih-Hua, Ted Chu, Keh-Han Wang, and Chii-Jau Tang. "Study of solitary-wave-induced fluid motions and vortices in a cavity using a two-dimensional viscous flow model." Journal of Engineering Mechanics 137, no. 11 (2011): 769-778.