Vertical Distribution of Suspended Sediments above Dense Plants in Water Flow
Abstract
:1. Introduction
2. Experimental Setup and Methods
2.1. Water Flume and Co-Ordinate System
2.2. Plant Configurations
2.3. Bulk Flow Condition and Fine Suspended Sediment Model
2.4. Measurement of Flow Velocity and the Observation of Plant Swaying
2.5. Diffusivities of Momentum of Flow and Fine Suspended Sediments
2.6. Settling Velocity of Fine Suspended Sediments
3. Results
3.1. Vertical Velocity Profile
3.2. Second Order Turbulent Momentum
3.3. Derivation of Turbulent Diffusivity of Flow
3.4. Equilibrium Equation between Turbulent Diffusion and Gravitational Settling of Fine Suspended Sediments
3.5. Experimental Results of the Profile of the Concentration of Suspended Sediments
4. Discussion
5. Conclusions
- (1)
- Over dense plants the velocity profile follows a semi-logarithmic law modified by and . The second order turbulent momentum () follows a negative linear function of and . Based on these two laws, a new function of turbulent diffusion coefficient () was derived.
- (2)
- Based on the dynamic balance between the upward turbulent diffusion and the downward gravitational settling, a double modified Rouse formula for the vertical distribution profile of fine suspended sediments was derived. The equation agrees well with experimentally observed data in the over-plant region.
- (3)
- With plants acting as a permeable bottom boundary of the flow over it, the fine sediments suspend or re-suspend from the top of the plants. In the above-plant region, the validation of the – double-parameter modified Rouse formula indicates that turbulent diffusion controls the upward movement of sediment.
Author Contributions
Funding
Conflicts of Interest
References
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(m3 s−1) | (cm) | (m s−1) | (cm s−1) | (cm) | |||
---|---|---|---|---|---|---|---|
0.0096 | 20 | 0.12 | 0.00038 | 1.89 | 3.1 | 6.45 | 0.775 |
Cases | (mm s−1) | (g L−1) | |||
---|---|---|---|---|---|
36 | 1.866 | 0.84 | 22.5 | 0.18 | |
59 | 2.100 | 2.26 | 8.4 | 0.23 | |
80 | 2.164 | 4.16 | 4.5 | 0.28 |
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Li, Y.; Xie, L.; Su, T.-c. Vertical Distribution of Suspended Sediments above Dense Plants in Water Flow. Water 2020, 12, 12. https://doi.org/10.3390/w12010012
Li Y, Xie L, Su T-c. Vertical Distribution of Suspended Sediments above Dense Plants in Water Flow. Water. 2020; 12(1):12. https://doi.org/10.3390/w12010012
Chicago/Turabian StyleLi, Yanhong, Liquan Xie, and Tsung-chow Su. 2020. "Vertical Distribution of Suspended Sediments above Dense Plants in Water Flow" Water 12, no. 1: 12. https://doi.org/10.3390/w12010012