IAHR, founded in 1935, is a worldwide independent member-based organisation of engineers and water specialists working in fields related to the hydro-environmental sciences and their practical application. Activities range from river and maritime hydraulics to water resources development and eco-hydraulics, through to ice engineering, hydroinformatics, and hydraulic machinery.
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You are here : eLibrary : IAHR World Congress Proceedings : 33rd Congress - Vancouver (2009) : Topic A: Advances in the Fundamentals of Water Science and Engineering : Flow and sand transport over an immobile gravel bed
Flow and sand transport over an immobile gravel bed
Author : D. G. Wren, E. J. Langendoen, and R. A. Kuhnle
Many dams in the USA and elsewhere have exceeded their design life and are being considered for remediation or removal, which will result in the reintroduction of fine sediments, often into coarse grained armored substrates, downstream of dams. The deposition of sand in the interstices of the gravel substrate complicates the prediction of sand transport due to difficulties in predicting the effective shear stress, the exposed area of the sand, and the resulting changes in water depth. An
adjustable-slope, recirculating laboratory flume was used to evaluate the effects of a stepwise addition of sand to an immobile gravel bed on the properties of flow and sediment transport. Detailed measurements of fluid velocity, sand transport rate, bed texture, and bed topography were collected for four different discharges (Fr=0.1, 0.3, 0.5, and 0.6). A Laser Doppler Anemometer and an Acoustic Doppler Velocimeter were used to measure mean and turbulent flow quantities while a flow-through density cell and physical samples were used to monitor sand transport. Additions of
sand had no measurable effect on flow structure until the depth of sand was approximately 5 cm below the top of the gravel layer. It was found that elevation of the sand bed relative to the top of the gravel and grain shear stress were the major factors controlling the rate of sand transport.
File Size : 779,310 bytes
File Type : Adobe Acrobat Document
Chapter : IAHR World Congress Proceedings
Category : 33rd Congress - Vancouver (2009)
Article : Topic A: Advances in the Fundamentals of Water Science and Engineering
Date Published : 09/08/2009
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