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Thomas N. Keefer

Publications and source records attributed to Thomas N. Keefer.

6 recordsLinked to original sources
USGS1979

Modeling highly transient flow, mass, and heat transport in the Chattahoochee River near Atlanta, Georgia

A coupled flow-temperature model has been developed and verified for a 27.9-km reach of the Chattahoochee River between Buford Dam and Norcross, Ga. Flow in this reach of the Chattahoochee is continuous but highly regulated by Buford Dam, a flood-control and hydroelectric facility located near Buford, Ga. Calibration and verification utilized two sets of data collected under highly unsteady discharge conditions. Existing solution techniques, with certain minor improvements, were applied to verify the existing technology of flow and transport modeling. The linear, implicit finite-difference flow model was calibrated by use of a depth profile obtained at steady low flow and unsteady flow data obtained in March 1976. During the calibration period, the model was generally able to reproduce observed stages to within 0.15 m and discharges at less than 100 m 3 /s, to within 5 percent. Peak discharges of about 200 m 3 /s were under-estimated by about 20 percent. During the verification period, October 1975, the flow model reproduced observed stage changes to within about 0.15 m, and its timing and over-all performance was considered to be very good. Dye was added to the upstream end of the river reach at a constant rate while the river flow was highly unsteady. The numerical solution of either the conservative or nonconservative form of the mass-transport equation did an excellent job of simulating the observed concentrations of dye in the river. The temperature model was capable of predicting temperature changes through this reach of as large as 5.8?C with a RMS (root-mean-square) error of 0.32?C in October 1975 and 0.20?C in March 1976. Hydropulsation has a significant effect on the water temperature below Buford Dam. These effects are very complicated because they are quite dependent on the timing of the release with respect to both the time of day and past releases.

Georgia↗
USGS1979

Probable hydrologic effects of a hypothetical failure of Mackay Dam on the Big Lost River Valley from Mackay, Idaho to the Idaho National Engineering Laboratory

Mackay Dam is an irrigation reservoir on the Big Lost River, Idaho, approximately 7.2 kilometers northwest of Mackay, Idaho. Consequences of possible rupture of the dam have long concerned the residents of the river valley. The presence of reactors and of a management complex for nuclear wastes on the reservation of the Idaho National Engineering Laboratory (INEL), near the river , give additional cause for concern over the consequences of a rupture of Mackay Dam. The objective of this report is to calculate and route the flood wave resulting from the hypothetical failure of Mackay Dam downstream to the INEL. Both a full and a 50 percent partial breach of this dam are investigated. Two techniques are used to develop the dam-break model. The method of characteristics is used to propagate the shock wave after the dam fails. The linear implicit finite-difference solution is used to route the flood wave after the shock wave has dissipated. The time of travel of the flood wave, duration of flooding, and magnitude of the flood are determined for eight selected sites from Mackay Dam, Idaho, through the INEL diversion. At 4.2 kilometers above the INEL diversion, peak discharges of 1,550.2 and 1,275 cubic meters per second and peak flood elevations of 1,550.3 and 1,550.2 meters were calculated for the full and partial breach, respectively. Flood discharges and flood peaks were not compared for the area downstream of the diversion because of the lack of detailed flood plain geometry. (Kosco-USGS)

Idaho↗
USGS1977

Routing of stormwater flows through storm drains

Storm-drain flow-routing methods based on kinematic-wave routing and storage-routing methods are compared with the MLSR (multiple-linearization storm-drain routing) method for hypothetical circular pipe problems. The MLSR method, based on a diffusion-wave routing concept, is shown to give very good results without incurring the numerical solution or damping problems of other methods.

Journal of Research of the U.S. Geological Survey↗
USGS1974

Investigation of diffusion in open-channel flows

This investigation examines the interrelation between turbulent diffusion, dispersion, and the statistical properties of turbulence in an open-channel flow. The results of the study substantiate Philip's concept relating the ratio of Eulerian to estimated Lagrangian time scales and the reciprocal of the longitudinal intensity of turbulence. The relation may be used to predict coefficients of longitudinal turbulent diffusion at the water surface and in the flow field, A similar concept using an integral scale based on the longitudinal intensity of turbulence may be used to predict coefficients of both surface and depth-averaged turbulent diffusion in three coordinate directions. Longitudinal space-time velocity correlation measurements can be used to predict the Lagrangian time scale only under limited conditions. Within the range of conditions studied, longitudinal diffusion accounted for 4 to 13 percent of the one-dimensional dispersion process.

Journal of Research of the U.S. Geological Survey↗
USGS1971

The relation of turbulence to diffusion in open-channel flows

This investigation examines the interrelation between turbulent diffusion, dispersion, and the statistical properties of turbulence in an open-channel flow. The experiments were conducted in a 3. 87- foot wide flume over four boundary roughnesses. The results are from studies made of: (1) the influence of turbulence on the vertical and lateral diffusion of plumes of heated water and a neutrally-buoyant salt solution from a point source at the mid-depth of flow; (2) the velocity concentration covariance along the axis of a salt solution plume using a single-electrode conductivity probe and hot-film sensor; (3) lateral and longitudinal surface diffusion measured by dropping polyethylene particles on the water surface; and (4) longitudinal space-time velocity correlation measurements. The results of the study substantiate Philip's concept relating the ratio of Eulerian to estimated Lagrangian time scales and the reciprocal of the longitudinal intensity of turbulence. The relation is used to predict coefficients of longitudinal turbulent diffusion at the water surface and in the flow field. A similar concept using an integral time scale based on the longitudinal intensity of turbulence is used to predict coefficients of both surface and depth-averaged turbulent diffusion in three coordinate directions for heated water and neutrally buoyant jets of salt solution. Longitudinal space-time velocity correlation measurements can be used to predict the Lagrangian time scale only under limited conditions. For this study the Lagrangian scale was underpredicted by 250 percent. A model is developed for the behavior of the longitudinal velocity concentration covariance along the axis of a plume of neutrally-buoyant salt solution. The covariance measurements are accurate to ±20 percent . The boussinesq model of scalar transport is verified with an accuracy of ±25 percent by comparing diffusion coefficients from (1) the velocity concentration covariance measurements with (2) those obtained at the water surface using floating particles. The hot-film single-electrode conductivity probe method for measuring the covariance offers a new tool to experimenters in turbulent mass transfer. Under the range of conditions studied, longitudinal diffusion accounts for 4 to 13 percent of the one-dimensional dispersion process. Predictions of the dispersion coefficient by formulas such as Elder's were in error by as much as 50 percent. The exponent in the power-law equation describing the decay of scalar quantities downstream of a jet is a linear function of the shear velocity of the channel. The length of the core region of a jet is a power-law function of the jet strength with the exponent depending on boundary roughness.

Open-File Report↗