Near-bed turbulence characteristics in unsteady hydrograph flows over mobile and immobile gravel beds

Jonathan Kean, Alan Cuthbertson, Lindsay Beevers

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

Improvements to current deterministic sediment transport prediction methods requires enhanced understanding of the changes in near-bed turbulent flowcharacteristics occurring during the unsteady hydrograph flow conditions, under which sediment transport is most likely to occur. This paper investigates specifically at relative influence of mobile and immobile bed conditions on the near-bed turbulent structure, focusing specifically on the generation of so-called burst and sweep events, as well as the reciprocal influence of unsteady flow on the nature of these turbulent flow events over both mobile and immobile gravel beds. Quadrant analysis is used to determine the number and strength of turbulent burst and sweep events from detailed three-dimensional ADV velocity data collected over both types of bed. Results indicate that the mobile bed experiences less, but higher magnitude, near-bed burst and sweep events compared to the immobile bed. Further consideration of the results using a hole-size analysis within the quadrant plots may permit the correlation with observed higherorder turbulence events with sediment transport under unsteady hydrograph flows. In this respect, the results demonstrated that higher strength, rather than a higher volume, of turbulent burst/sweep events are found during unsteady flow conditions that are favorable for sediment transport.

Original languageEnglish
Title of host publicationRiver Sedimentation - Proceedings of the 13th International Symposium on River Sedimentation, ISRS 2016
EditorsSilke Wieprecht, Stefan Haun, Karolin Weber, Markus Noack, Kristina Terheiden
PublisherCRC Press/Balkema
Pages259-266
Number of pages8
ISBN (Print)9781138029453
Publication statusPublished - Sep 2016
Event13th International Symposium on River Sedimentation, ISRS 2016 - Stuttgart, Germany
Duration: 19 Sep 201622 Sep 2016

Publication series

NameRiver Sedimentation - Proceedings of the 13th International Symposium on River Sedimentation, ISRS 2016

Conference

Conference13th International Symposium on River Sedimentation, ISRS 2016
CountryGermany
CityStuttgart
Period19/09/1622/09/16

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  • Cite this

    Kean, J., Cuthbertson, A., & Beevers, L. (2016). Near-bed turbulence characteristics in unsteady hydrograph flows over mobile and immobile gravel beds. In S. Wieprecht, S. Haun, K. Weber, M. Noack, & K. Terheiden (Eds.), River Sedimentation - Proceedings of the 13th International Symposium on River Sedimentation, ISRS 2016 (pp. 259-266). (River Sedimentation - Proceedings of the 13th International Symposium on River Sedimentation, ISRS 2016). CRC Press/Balkema.