Korean Journal of Ecology and Environment (생태와환경)

The Korean Society of Limnology (한국수생태학회)
권호 표지

A Numerical Study on Turbulent Damping Effect due to Density Stratification of Cohesive and Noncohesive Sediment

점착성 및 비점착성 유사의 밀도성층화에 따른 난류 영향에 대한 수치연구

  • Received : 2011.01.27
  • Accepted : 2011.03.08
  • Published : 2011.03.31
Download PDF
⟨ Previous Next ⟩

Abstract

This numerical study aims to investigate the effect of cohesive sediment on turbulence structure due to density stratification. The transport model for cohesive sediment incorporated with flocculation model has been selected and calculates the concentration, fluid momentum, and turbulence. From the model results, it is known that suspension of sediment decreases turbulence intensity. It is also found that cohesive sediment has a relatively weak effect on turbulence damping compared to noncohesive sediment. The low settling velocity and more suspension of cohesive sediment are considered to be mechanisms of this behavior. Richardson number determined with results of this study quantitatively shows that cohesive sediment causes less stable density stratification condition and, as a result, the turbulence structure is less damped compared to the case of noncohesive sediment.

Keywords

Acknowledgement

Grant : 하구역종합관리시스템개발

References

  1. 박성은, 김동선, 이충일, 황재동, 윤종휘, 조규대. 2003. 성층화된 수로에서 3차원 Hill에 의한 유속장 변동. 한국해양환경안전학회지 9(2): 73-77.
  2. 양경수, 박찬욱, 이승수. 2004. 구 후류에 미치는 유동장 밀도 성층화 영향 전산 해석. 대한기계학회논문집B 28(5): 553-559.
  3. Biggs, C.A. and P.A. Lant. 2000. Floc rupture and turbulence: a framework for analysis. Chemical Engineering Science 59: 2521-2534.
  4. Dyer, K.R. 1997. Estuaries: A Physical Introduction, 2nd ed. John Wiley & Sons Ltd., England.
  5. Hsu, T.-J., P.A. Traykovski and G.C. Kineke. 2007. On modeling boundary layer and gravity-driven fluid mud transport. Journal of Geophysical Research DOI:0.1029/2006 JC003719.
  6. Khelifa, A. and P.S. Hill. 2006. Models for effective density and settling velocity of flocs. Journal of Hydraulic Research 44(3): 390-401. https://doi.org/10.1080/00221686.2006.9521690
  7. Krishnappan, B.G. and J. Marsalek. 2002. Modelling of flocculation and transport of cohesive sediment from an on-stream stormwater detention pond. Water Research 36: 3849-3859. https://doi.org/10.1016/S0043-1354(02)00087-8
  8. Maggi, F., F. Mietta and J.C. Winterwer. 2007. Effect of variable fractal dimension on the floc size distribution suspended cohesive sediment. Journal of Hydrology 343: 43-55. https://doi.org/10.1016/j.jhydrol.2007.05.035
  9. McAnally, W.H. and A.J. Mehta. 2000. Aggregation rate of fine sediment. Journal of Hydraulic Engineering 126: 883-892. https://doi.org/10.1061/(ASCE)0733-9429(2000)126:12(883)
  10. McCave, I.N. 1984. Size spectra and aggregation of suspended particles in the deep ocean. Deep Sea Research 31(4): 329-352. https://doi.org/10.1016/0198-0149(84)90088-8
  11. Mehta, A.J. and Y. Li. 1997. A PC-based short course on fine-grained sediment transport engineering. Coastal and Oceanography Eng. Dept., University of Florida.
  12. Milligan, T.G. 1996. In situ particle (floc) size measurements with the benthos plankton silhouette camera. Journal of Sea Research 36(1-2): 93-100.
  13. O'Melia, C.R. 1980. Aquasols: the behaviour of small particles in aquatic systems. Environmental Science and Technology 14(9): 1052-1060. https://doi.org/10.1021/es60169a601
  14. Sanford, L.P. and J.P.-Y. Maa. 2001. An unified erosion formulation for fine sediments. Marine Geology 179: 9-23. https://doi.org/10.1016/S0025-3227(01)00201-8
  15. Son, M. and T.-J. Hsu. 2008. Flocculation model of cohesive sediment using variable fractal dimension. Environmental Fluid Mechanics 8(1): 55-71. https://doi.org/10.1007/s10652-007-9050-7
  16. Son, M. and T.-J. Hsu. 2009. The effect of variable yield strength and variable fractal dimension on flocculation of cohesive sediment. Water Research 43: 3582-3592. https://doi.org/10.1016/j.watres.2009.05.016
  17. Son, M. and T.-J. Hsu. 2010. Idealized study on cohesive sediment flux by tidal asymmetry. Environmental Fluid Mechanics DOI:10.1007/s10652-010-9193-9.
  18. Son, M. and T.-J. Hsu. 2011. The effects of flocculation and bed erodibility on modeling cohesive sediment resuspension. Journal of Geophysical Research 116(C03021) DOI:10.1029/2010JC 006352.
  19. Spicer, P.T., S.E. Pratsinis, J. Raper, R. Amal, G. Bushell and G. Meesters. 1998. Effect of shear schedule on particle size, density, and structure during flocculation in stirred tanks. Powder Technology 97: 26-34. https://doi.org/10.1016/S0032-5910(97)03389-5
  20. Sternberg, R.W. 1968. Friction factor in tidal channels with differing bed roughness. Journal of Marine Geology 6: 243-260. https://doi.org/10.1016/0025-3227(68)90033-9
  21. Stolzenbach, K.D. and M. Elimelich. 1994. The effect of density on collisions between sinking particles: implications for particle aggregation in the ocean. Journal of Deep Sea Research I 13: 409-419.
  22. Tsai, C.H. and S.C. Hwang. 1995. Flocculation of sediment from the Tanshui River estuary. Marine Freshwater Research 46: 383-392.
  23. van der Ham R. and J.C. Winterwerp. 2001. Turbulent exchange of fine sediments in a tidal channel in the Ems/ Dollard estuary. Part II. Analysis with a 1DV numerical model. Continental Shelf Research 21: 1629-1647. https://doi.org/10.1016/S0278-4343(01)00011-5
  24. van Leussen, W. 1994. Estuarine macroflocs and their role in fine-grained sediment transport. PhD dissertation, University of Utrecht.
  25. Winterwerp, J.C. 1998. A simple model for turbulence induced flocculation of cohesive sediment. Journal of Hydraulic Research 36(3): 309-326. https://doi.org/10.1080/00221689809498621
  26. Winterwerp, J.C. 2001. Stratification effects by cohesive and noncohesive sediment. Journal of Geophysical Research 106(C10): 22559-22574. https://doi.org/10.1029/2000JC000435
  27. Winterwerp, J.C. and W.G.M. van Kesteren. 2004. Introduction to the Physics of Cohesive Sediments in the Marine Environment. Elsevier, NewYork.
  28. Xu, F., D.-P. Wang and N. Riemer. 2010. An idealized model study of flocculation on sediment trapping in an estuarine turbidity maximum. Continental Shelf Research 30: 1314-1323. https://doi.org/10.1016/j.csr.2010.04.014