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Temperature effects in alluvial streams

Taylor, Brent D. (1971) Temperature effects in alluvial streams. California Institute of Technology , Pasadena, CA. (Unpublished)

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A laboratory investigation was conducted to determine the effects of water temperature on sediment discharge close to the bed (bed-load discharge), and on bed roughness and geometry in alluvial, open-channel flows. Three types of experiments were made: 1) Low-transport, flat-bed experiments in which all of the sediment discharged moved as bed load; 2) high-transport, flat-bed experiments with fine sands wherein there was considerable suspended sediment discharge; and 3) a series of experiments where the discharge was kept constant and the velocity varied to produce ripple, dune, and flat-bed configurations. The experiments were made in pairs. In each pair the velocity and depth were the same or nearly the same, but in one experiment the water temperature was from 15°C to 20°C higher than in the other. It was found that in low-transport, flat-bed flows where particle transport is by rolling and sliding along the bed, a 15°C to 20°C increase in water temperature can produce a relatively large change in sediment discharge. The nature of this change depends on the flow condition at the bed. With hydrodynamically smooth flow there is an increase in sediment discharge with increase in water temperature; whereas in transition from smooth to rough an increase in water temperature effects a reduction in sediment discharge. With fully-rough flow which obtains at boundary Reynolds numbers larger than approximately 200, sediment discharge does not depend on water temperature. A phenomenological explanation has been presented for these observed temperature effects on sediment discharge. In high-transport, flat-bed flows with suspended sediment transport, it was observed that the temperature effects on bed-load discharge are qualitatively the same as those which obtain in low-transport, flat-bed flows of approximately the same boundary Reynolds numbers. It was also found that under certain flow conditions a change in water temperature alone can cause a change in bed form. The nature of this change in bed form seems to be related to the boundary Reynolds numbers R'_(*b) of the flows. For R'_(*b) less than a value near 8 bed form transitions were accomplished at lower velocities in a warm water flow than in a cold water flow at the same discharge; whereas for larger values of R'_(*b) contrary temperature effects on bed form transitions have been observed.

Item Type:Report or Paper (Technical Report)
Additional Information:The writer would like to express deep appreciation to his advisor Professor Vito A. Vanoni for kind guidance, encouragement, and generous assistance during this investigation. The writer would also like to thank Professor Norman H. Brooks for initially interesting him in graduate study at Caltech; and he and Professor Fredric Raichlen for their helpful interest in the temperature-effects study. During the experimental investigation and thesis preparation skillful and considerate assistance was given by Mrs. Arvilla F. Krugh, Mrs. Patricia A. Rankin, Mr. Elton F. Daly, Mr. Robert L. Greenway, Mr. Carl A. Green, Jr., Mr. Ronald G. Patterson, and Mr. Carl T. Eastvedt. To each of these people the writer offers his sincere thanks. The writer wishes also to thank the Civil Engineering Department at the California Institute of Technology for making possible four years of graduate study in an atmosphere of creativity and excellence. This research was supported by the National Science Foundation, Grant No. GK 3910. This report was submitted by the writer on August 2, 1971 as a thesis with the same title to the California Institute of Technology in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Civil Engineering.
Group:W. M. Keck Laboratory of Hydraulics and Water Resources
Record Number:CaltechKHR:KH-R-27
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ID Code:26013
Deposited By: Imported from CaltechKHR
Deposited On:06 Jan 2010
Last Modified:15 Jul 2021 23:25

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