Comparison of settling-velocity-based formulas for threshold of sediment motion
The critical condition for incipient sediment motion is formulated in this note based on the settling velocity. The formula obtained is simple, relating the ratio of critical shear velocity to settling velocity to the dimensionless sediment diameter. Comparisons are then made with other settling-vel...
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| Format: | Journal Article |
| Language: | English |
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2012
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| Online Access: | https://hdl.handle.net/10356/83699 http://hdl.handle.net/10220/7644 |
| _version_ | 1811679859154354176 |
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| author | Cheng, Nian-Sheng |
| author2 | School of Civil and Environmental Engineering |
| author_facet | School of Civil and Environmental Engineering Cheng, Nian-Sheng |
| author_sort | Cheng, Nian-Sheng |
| collection | NTU |
| description | The critical condition for incipient sediment motion is formulated in this note based on the settling velocity. The formula obtained is simple, relating the ratio of critical shear velocity to settling velocity to the dimensionless sediment diameter. Comparisons are then made with other settling-velocity based formulas available in the literature. To facilitate the computation of the effective near-bed velocity at the threshold condition, a generalized law-of-the-wall function is proposed for predicting the velocity distribution under various boundary conditions. This study demonstrates that the settling velocity is equivalent to the critical near-bed velocity, which is experienced by a typical bed sediment particle under the threshold condition, but only for large sediment sizes such as sand and gravel. Comparison results show that Yang's formula is suitable for flows with small flow depth relative to sediment size while Le Roux's formula may overestimate the threshold condition for fine particles by up to 30%. |
| first_indexed | 2024-10-01T03:15:51Z |
| format | Journal Article |
| id | ntu-10356/83699 |
| institution | Nanyang Technological University |
| language | English |
| last_indexed | 2024-10-01T03:15:51Z |
| publishDate | 2012 |
| record_format | dspace |
| spelling | ntu-10356/836992020-03-07T11:43:37Z Comparison of settling-velocity-based formulas for threshold of sediment motion Cheng, Nian-Sheng School of Civil and Environmental Engineering DRNTU::Engineering::Civil engineering The critical condition for incipient sediment motion is formulated in this note based on the settling velocity. The formula obtained is simple, relating the ratio of critical shear velocity to settling velocity to the dimensionless sediment diameter. Comparisons are then made with other settling-velocity based formulas available in the literature. To facilitate the computation of the effective near-bed velocity at the threshold condition, a generalized law-of-the-wall function is proposed for predicting the velocity distribution under various boundary conditions. This study demonstrates that the settling velocity is equivalent to the critical near-bed velocity, which is experienced by a typical bed sediment particle under the threshold condition, but only for large sediment sizes such as sand and gravel. Comparison results show that Yang's formula is suitable for flows with small flow depth relative to sediment size while Le Roux's formula may overestimate the threshold condition for fine particles by up to 30%. Accepted version 2012-03-21T08:17:14Z 2019-12-06T15:28:19Z 2012-03-21T08:17:14Z 2019-12-06T15:28:19Z 2008 2008 Journal Article Cheng, N. S. (2008). Comparison of Settling-Velocity-Based Formulas for Threshold of Sediment Motion. Journal of Hydraulic Engineering, 134(8), 1136-1141. 1943-7900 (online) https://hdl.handle.net/10356/83699 http://hdl.handle.net/10220/7644 10.1061/(ASCE)0733-9429(2008)134:8(1136) en Journal of hydraulic engineering © 2008 ASCE. This is the author created version of a work that has been peer reviewed and accepted for publication by Journal of Hydraulic Engineering, American Society of Civil Engineers. It incorporates referee’s comments but changes resulting from the publishing process, such as copyediting, structural formatting, may not be reflected in this document. The published version is available at: [DOI: http://dx.doi.org/10.1061/(ASCE)0733-9429(2008)134:8(1136)]. 19 p. application/pdf |
| spellingShingle | DRNTU::Engineering::Civil engineering Cheng, Nian-Sheng Comparison of settling-velocity-based formulas for threshold of sediment motion |
| title | Comparison of settling-velocity-based formulas for threshold of sediment motion |
| title_full | Comparison of settling-velocity-based formulas for threshold of sediment motion |
| title_fullStr | Comparison of settling-velocity-based formulas for threshold of sediment motion |
| title_full_unstemmed | Comparison of settling-velocity-based formulas for threshold of sediment motion |
| title_short | Comparison of settling-velocity-based formulas for threshold of sediment motion |
| title_sort | comparison of settling velocity based formulas for threshold of sediment motion |
| topic | DRNTU::Engineering::Civil engineering |
| url | https://hdl.handle.net/10356/83699 http://hdl.handle.net/10220/7644 |
| work_keys_str_mv | AT chengniansheng comparisonofsettlingvelocitybasedformulasforthresholdofsedimentmotion |