Browsing by Author "Sunada, Daniel K., committee member"

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Open Access
Advective-diffusive gaseous transport in porous media: the molecular diffusion regime
(Colorado State University. Libraries, 1993) Farr, John Merritt, author; McWhorter, David B., advisor; Weeks, Edwin P., 1936-, committee member; Sunada, Daniel K., committee member; Lenz, Terry G., committee member
Traditional mathematical models for advective-diffusive transport in porous media fail to represent important physical processes when fluid density depends on composition. Such is the case for gas mixtures comprised of species with differing molecular masses, such as found in the vadose zone near chlorinated hydrocarbon sources. To address problems of this nature, a more general advection-diffusion (A-D) model is presented, which is valid for porous media with permeabilities exceeding 10-10 cm2 (where Klinkenberg and Knudsen effects are negligible). The new mathematical model is derived by thermodynamic means, based on identifying the meaning of Darcy's advective reference velocity in terms of a weighted average of species drift velocities~ The resulting model has no additional parameters, and introduces no additional complexity or nonlinearity when compared to the traditional A-D model most commonly used in hydrology and environmental science. Because the form of traditional A-D models is retained, the new formulations fit readily into existing numerical simulators for the solution of subsurface transport problems. The new model is equivalent to the Dusty-Gas Model of Mason et al. (1967) for cases where the molecular diffusion regime prevails and pressure, temperature, and forced diffusion are negligible. Further support of the model is provided by hydrodynamic analysis, accounting for the diffusive-slip flux identified by Kramers and Kistemaker (1943). The new model is analytically compared to two existing A-D models, one from the hydrology literature, where Darcy's law is assumed to yield a mass-average velocity, and one from the chemical engineering literature, where Darcy's law is assumed to yield a mole-average velocity. Significant differences are shown to exist between the three transport models. The new model is shown to match closely with the experimental data of Evans et al. (1961a), while the existing A-D models are shown to fail in this regard.
Open Access
Dispersion in bi-modal oil shales
(Colorado State University. Libraries, 1982) Bryant, Mark A., author; McWhorter, David B., advisor; Sunada, Daniel K., committee member; Ward Robert C., committee member
A series of leaching column experiments were conducted using 3 different grain sizes of spent oil shale from the Paraho retorting process. Electrical conductivity breakthrough data produced at 3 different seepage velocity rates were analyzed with the help of a least squares curve fitting computer model, CFITIM, developed by Van Genuchten (1981). Emphasis was placed on the identification of transport mechanisms which could explain the observed asymetry of the breakthrough curves. Comparison of the column breakthrough curves to a analytical dispersion model which took into account a micro pore diffusion transfer mechanism, produced poor correlation. When a linear sorption transfer mechanism was coupled with a micro pore diffusion transfer mechanism in the analytical model a much better match of the breakthrough data was obtained. The analytical model may prove useful in the development of a standard leaching column test procedure, however, it is suspected that the model parameters have little physical significance and therefore can only be used in fitting the breakthrough curves.
Open Access
Synthesis of design operation and management of surface irrigation conveyance systems
(Colorado State University. Libraries, 1984) Sritharan, Subramaniaiyer, author; Richardson, E. V., advisor; Clyma, Wayne, advisor; Fontane, Darrell G.. committee member; Sunada, Daniel K., committee member; Hall, W. A., committee member
A theory for the design of conveyance systems, synthesizing with it the operation and management and set in an interdisciplinary mode is proposed. The theory involving eleven steps is required in the development of solutions to six basic problems hitherto inadequately addressed. These solutions are given in the following six modules of the dissertation: (i) Optimal Turnout Area Module, (ii) Turnout Area Water Requirement Module, (iii) Project Scale Farm Design Module, (iv) Ground Water Interaction Module, (v) Water Issue Strategy Module and (vi) Hydraulic Simulation Module. The problem of optimal turnout area was studied using causal processes theory (of mathematical sociology). Independence models and first order Markovian dependence models describing farmer behavior in the turnout area were studied. The turnout area water requirement problem was studied using a probability based design evapotranspiration computation procedure. Requirement depths were obtained by deriving optimal scheduling in space and time applying dynamic programming, using recent crop production functions and considering recent soil moisture stress models. Water requirements in terms of depth were converted to flow requirements in an optimal manner considering the hydraulics of the application system again using a two stage programming approach. Requirement efficiency and deep percolation ratio functions were developed for level borders using a zero-inertia model for four different soil types and for furrows using SCS approaches for the use in the model. Ground water interactions in the irrigated areas were studied using a linearized Boussinesq equation and Green's Function approach. Recharge excitation was represented by a finite Fourier series fitted to the excitations obtained using the developed deep percolation functions and the appropriate boundary conditions. Long term water table build up was studied using this approach for any detrimental effects due to application system design. Different water issue strategies and their optimality/acceptability were studied. The optimal strategy for a Rotational Water Issue (RWI) was that the rotations be as low in the hierarchy of the canal system as possible and the capacities depended on the irrigation intervals. The problem of hydraulic simulation was studied using the linearized diffusive wave equation for canal flow. The integral method was found to compare well with the analytical solution and was used for the solution of the advance problem. Delay times in releasing fixed steps of flow were computed using this approach. The operational criteria and necessary control measures were developed. The solution procedures were applied to a sample hypothetical project area and found to be applicable.
Open Access
Water quality hydrology on surface mined watersheds
(Colorado State University. Libraries, 1976) Rowe, Jerry W., author; Longenbaugh, Robert A., advisor; McWhorten, David B., committee member; Sunada, Daniel K., committee member
Water quality and discharge on four watersheds disturbed by surface coal mining at the Edna Mine in northwestern Colorado have been monito red for about three years. Water quality and discharge have also been monitored in an adjacent stream at points above and below the entrance of mine drainage into the stream. Dissolved solids inflow to the stream between these two points equaled 6.lx106 kg in 1974 and 5.3x106 kg in 1975 for an increase in dissolved solids load of two to three times along the reach of the stream adjacent to the mine. About 70 to 80 percent of the dissolved solids inflow occurs in April, May, and June. During spring runoff dissolved solids reach concentrations exceeding 700 mg/ℓ at the downstream monitoring site with corresponding concentrations of less than 150 mg/ℓ at the upstream site. Dissolved solids concentrations in combined runoff on the four mine watersheds ranged from annual averages of 1200 mg/ℓ to 3000 mg/ℓ. The pre-mining concentration of dissolved solids in combined runoff is estimated at 460 mg/ℓ with the higher concentrations on the mine watersheds attributable to the disturbance caused by mining. Mining increases the depth of water percolation from several meters or less on undisturbed land to about 20 meters on mined land. Data show that the disturbed geologic material in the spoils contains large quantities of soluble salts. A single-equation model based upon water and mass balances has been developed which can predict the average annual TDS concentration of combined surface and subsurface runoff from a mined watershed. The model incorporates three hydrologic parameters, three chemical parameters, and the fraction of land disturbed by mining. Concentrations predicted using the model on the Edna Mine watersheds had an average error of about 9 percent from the measured concentrations. Parameters in the model can be adjusted to simulate the effects of varied climatic and hydrologic conditions that may result from reclamation efforts. The model may prove to be a useful tool for the planning and management of water resources on surface mine lands.