Investigation into the hydraulic performance of dam stilling basins with different configurations of block appurtenances

Simmonds, Jonathan (2016) Investigation into the hydraulic performance of dam stilling basins with different configurations of block appurtenances. BEng dissertation, University of Portsmouth.

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    Stilling basins are integral features within dam structures that are used to dissipate energy of reservoir overflow discharge from the spillway so that the water can safely flow downstream via the river channel. The stilling basin is able to dissipate energy by means of a hydraulic jump which forms along the basin apron, but it is essential that the basin length is sufficient to mitigate river channel erosion by scour. Typically, stilling basins utilise obstruction appurtenances, including chute blocks, baffle blocks and end sills, and these are valuable to improving the hydraulic performance of the basin in respect to energy dissipation and the length of the hydraulic jump.
    Optimising the hydraulic performance of stilling basins plays a vital role in providing economically justifiable solutions with short basins which use minimal resources. The true effectiveness of different configurations of block appurtenances, also known as baffle blocks, on improving the hydraulic performance of stilling basins is debated with related studies, of which there are few, deriving contradictory assumptions, particularly in respect to the significance of the number of block rows. A limited number of studies have examined the aspect of block configurations and few studies have clarified its importance, thus this investigation will serve to input a clear understanding into this area of research.
    This paper outlines a laboratory-based experimental method used to enable investigation into the hydraulic performance of dam stilling basins with different configurations of baffle blocks. The resulting data highlights correlations between the different configuration types to each of the hydraulic performance aspects. It was found that increasing the number of rows of blocks had a negligible effect on the energy dissipated, yet in contrast, increasing the number of rows had a significant effect of reducing the length of hydraulic jump and thus reducing the required length of stilling basin. Varying the lateral spacing between blocks was found to have differing impacts since reducing the lateral spacing increased energy dissipation, but by increasing the lateral spacing the length of jump significantly reduced. Varying the longitudinal spacing between block rows was found to affect energy dissipation and length of jump, but since a limited number of models were tested this would have to be investigated further to draw a valid conclusion. In addition, the resulting data suggests that the hydraulic performance aspects examined do not correlate with each other and this contradicts with existing literature, hence investigating this further may be valuable to understanding the effect of different configurations of baffle blocks on hydraulic performance.

    Item Type: Dissertation
    Departments/Research Groups: Faculty of Technology > School of Civil Engineering and Surveying
    Depositing User: Beth Atkins
    Date Deposited: 01 Sep 2016 12:45
    Last Modified: 01 Sep 2016 12:45

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