Froude characteristics of both dense granular and water flows in flume modelling
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One of the challenges associated with small-scale flume modelling is achieving dynamic similarity. Froude (Fr) scaling is commonly adopted to capture the bulk characteristics of a flowing medium. Although the Fr number cannot capture the micro-interactions of a flow medium, it is commonly adopted by engineers, due to its simplistic nature for characterising mass-wasting processes. Given the prevalence of Fr scaling, an improved understanding of the development of Fr characteristics for channelized surge flows is certainly warranted. A 5-m long rectangular flume model was adopted to carry out experiments using dense uniform dry granular and water flows, separately. Laser and photoconductive sensors, and high speed imagery were used to estimate flow velocity and thickness. Results reveal that the Fr behaviour of uniform dry sand and water flows is dependent on its energy-dissipation mechanism. The initial volume has a greater influence on suppression of Fr conditions compared to shallower channel inclinations for both granular and water flows. The major limitation of small-scale flume modelling lies in limited initial volumes. Limited initial volumes lead to shallow flow depths and results in the flow velocity controlling Fr development of the flow mass with transportation. Frictional materials are not favourable for developing low Fr numbers in flume modelling.
KeywordsFroude characteristics Flume modelling Dense granular flow Water flow Mass-wasting processes
The work described in this paper was supported by a grant from the Research Grants Council of the Hong Kong Special Administrative Region, China (HKUST 06/CRF/12R and T22-603/15 N). The authors would also like to acknowledge the support by the HKUST Jockey Club Institute of Advanced Study. Finally, we would like to acknowledge the constructive comments from the two anonymous reviewers of this paper.
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