Thesis (M.S. in mechanical engineering)--Washington State University, December 2005. / Includes bibliographical references (p. 32-33).

Subsurface drainage affects water table fluctuation patterns by removing the excess water from the soil. The annual average water table depths of the drained (A) and undrained (D) regimes are 0.83 and 0.48 m from the soil surface respectively. Subirrigation continuously provides water to the upper soil by capillary rise. The annual water table depths of the subirrigated regimes (B and C) are 0.61 and 0.70 m respectively. It is found that there is a significant curvilinear correlationship between the drainage flow rate and the water table height above the drain. Soil drainable porosity of different regimes was investigated by using the soil water balance approach. The average drainable porosity of regimes A and B are 6.0% and 4.9% from water table rise, and 5.9% and 4.5% from water table drawdown , respectively. Subirrigation adversely affects the soil drainable porosity. Soil drainable porosity is often considered as a constant. However, the results of this study indicate that it varies with the water table height above the drain. In the case of water table drawdown, this dependence can be successfully expressed by a negative exponential equation. In the case of water table rise, the correlation is not as significant, but there is still a trend that the drainable porosity decreases with the increase of the water table height above the drain. Evapotranspiration (ET) is often neglected in soil water balance models for the drain-able porosity determination. This may result in some errors. In this study, the potential ET rate was computed by the Penman and Hargreaves methods. These two methods give very similar ET values for the studied area. It is assumed that actual ET equals to the potential ET rate when the ground water table is close to the soil surface. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

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Porosity is known to be one of the primary factors controlling fatigue life and total elongation in cast aluminum components. The thrust of this study is to examine pore nucleation and growth effects for predicting gas microporosity in A356 plates. In this work, a solidification model is used to quantify and evaluate the discrepancy between experimental data and porosity calculated with different approaches. The first approach considers hydrogen supersaturation based on the transport of dissolved hydrogen and Sievert?s law. The second approach uses the hydrogen supersaturation calculated in the first approach combined with a local solidification time. The third approach considers a new hydrogen technique based on the transport of inclusions through the liquid metal and mushy zone. Computer simulations were performed modeling aluminum plate castings.

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