Laboratory Study on the Entrainment Process in Overflow
Abstract
:1. Introduction
2. Experimental Setup
3. Data and Method
4. Results
4.1. Velocity Fields
4.2. Vorticity Fields and Turbulent Dissipation
4.3. Entrainment Phenomena and Water Intrusion
5. Conclusions
- (1)
- The overflow will mix with their surroundings as they descend and spread out in this density gradient before they reach the bottom. When the overflow moves along the slope, it will generate vortices and entrainments. Due to the stability of the stratified environment, the vorticity does not dissipate rapidly, and there is an alternating phenomenon of positive and negative vorticity after the overflow leaves the slope. When reaching the bottom at a high velocity after a certain time, vortices continuously generate at the bottom due to the momentum obtained in the opposite direction.
- (2)
- Turbulent dissipation mainly occurs in the area along the slope and during the process of invading flow to the surrounding. There is a large turbulent dissipation after crossing the sill, where the instability caused by the shear between the gravity flow and the ambient water is the strongest. Another location of the extreme value of turbulent dissipation is the water layer with a density equivalent to that of overflow, where the direction of overflow velocity changes, resulting in significant velocity shear. Corresponding to the velocity field and vorticity field, the momentum keeps decreasing due to mixing and dissipation.
- (3)
- The entrainment parameter can reflect the entrainment process during the overflow sinking, which is calculated by the empirical formula. Therefore, there is a close relationship between the vertical gradient of the density and velocity of the overflow and the entrainment. The greater the density difference between overflow and background, the larger the entrainment parameter. When the injection flow velocity is high, strong entrainment occurs at the point where the overflow crosses the sill and at the front end of the overflow. From the experimental results, it can be seen that the larger the terrain slope, the smaller the entrainment parameter, which is due to gravity playing a dominant role.
Author Contributions
Funding
Acknowledgments
Conflicts of Interest
References
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1 | 2 | 3 | 4 | 5 | 6 | 7 | |
---|---|---|---|---|---|---|---|
Slope of sill (°) | 30 | 30 | 30 | 30 | 30 | 45 | 60 |
Injection rate (mL/s) | 0.65 | 0.65 | 0.65 | 0.55 | 0.75 | 0.65 | 0.65 |
Injection density (kg/m3) | 1050 | 1040 | 1060 | 1050 | 1050 | 1050 | 1050 |
Group number | a2, b2, c1 | a1 | a3 | b1 | b3 | c2 | c3 |
Density (kg/m3) | Injection Rate (mL/s) | Froude Number | Richardson Number |
---|---|---|---|
1040 | 0.55 | 0.6636 | 0.3143 |
1050 | 0.65 | 1.0393 | 0.3086 |
1060 | 0.75 | 1.2614 | 0.1661 |
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Hu, Q.; Yu, J.; Cao, Y.; Chen, X.; Meng, J.; Lv, X. Laboratory Study on the Entrainment Process in Overflow. J. Mar. Sci. Eng. 2023, 11, 1383. https://doi.org/10.3390/jmse11071383
Hu Q, Yu J, Cao Y, Chen X, Meng J, Lv X. Laboratory Study on the Entrainment Process in Overflow. Journal of Marine Science and Engineering. 2023; 11(7):1383. https://doi.org/10.3390/jmse11071383
Chicago/Turabian StyleHu, Qiyue, Jiahui Yu, Yong Cao, Xu Chen, Jing Meng, and Xianqing Lv. 2023. "Laboratory Study on the Entrainment Process in Overflow" Journal of Marine Science and Engineering 11, no. 7: 1383. https://doi.org/10.3390/jmse11071383
APA StyleHu, Q., Yu, J., Cao, Y., Chen, X., Meng, J., & Lv, X. (2023). Laboratory Study on the Entrainment Process in Overflow. Journal of Marine Science and Engineering, 11(7), 1383. https://doi.org/10.3390/jmse11071383