The effect of roughness configuration on velocity profiles in an artificial channel
โ Scribed by Wohl, Ellen E.; Ikeda, Hiroshi
- Publisher
- John Wiley and Sons
- Year
- 1998
- Tongue
- English
- Weight
- 254 KB
- Volume
- 23
- Category
- Article
- ISSN
- 0360-1269
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โฆ Synopsis
In order to determine the effect of bed roughness on velocity distribution, we used seven different configurations of bed roughness, with 16 test runs of varying discharge and slope for each configuration. For each run, one-dimensional velocity profiles were measured at 1cm vertical increments over the crest of the roughness element, and at intervals of 4โข25 cm downstream. Results indicate that velocity profile shape remains fairly constant for a given slope and roughness configuration as discharge increases. As slope increases, the profiles become less linear, with a much larger near-bed velocity gradient and a more pronounced velocity peak close to 0โข6 flow depth at the measurement point immediately downstream from the roughness element. The zone of large near-bed velocity gradients increases in both length and depth as roughness concentration decreases, up to a length/height ratio of about 9, at which point maximum flow resistance occurs. Longitudinal roughness elements do not create nearly as much flow resistance as do transverse elements. Rates of velocity increase suggest that roughness elements spaced at a length/height ratio of about 9 are most effective at creating flow resistance over a range of discharges in channels with steeper slopes.
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