KSCE Journal of Civil and Environmental Engineering Research (대한토목학회논문집)

Korean Society of Civil Engeneers (대한토목학회)
권호 표지
DOI QR코드

DOI QR Code

Impact of Secondary Currents on Solute Transport in Open-Channel Flows over Smooth-Rough Bed Strips

조(粗)·세립상(細粒床)의 연속구조를 갖는 개수로 흐름에서 오염물질 수송에 대한 이차흐름 영향 분석

  • 강형식 (한국건설기술연구원 하천.해안연구실) ;
  • 최성욱 (연세대학교 사회환경시스템공학부) ;
  • 김규호 (한국건설기술연구원 하천.해안연구실)
  • Received : 2008.11.05
  • Accepted : 2009.01.02
  • Published : 2009.01.31
Download PDF
⟨ Previous Next ⟩

Abstract

This paper presents a numerical investigation of the impact of the secondary currents on solute transport in open-channel flows. The RANS model with Reynolds stress model is used for flow modeling, and the GGDH(generalized gradient diffusion hypothesis) model is used to close the scalar transport equation. Using the developed model, the impact of secondary currents on solute transport in open channel flows over smooth-rough strip is investigated. Through numerical experiments, the secondary currents are found to affect the solute spreading, leading a movement of the position of the peak concentration and a skewed distribution of solute concentration. Due to the lateral flow of secondary currents near the free surface, the concentration at the rough strip is found to be larger than that at the smooth strip bed. The solute at the rough strip is more rapidly transported than smooth bed. A magnitude analysis of the solute transport rate in scalar transport equation is also carried out to investigate the effect of secondary currents and scalar flux on the concentration distribution.

본 연구에서는 개수로 흐름에서 오염물질 이동 현상에 대한 이차흐름의 영향을 분석하였다. 운동량 방정식과 스칼라 수송 방정식에서의 난류 폐합을 위해 레이놀즈응력 모형 및 GGDH 모형을 사용하였다. 개발된 모형을 이용하여 조 세립상의 횡방향 연속구조를 갖는 개수로 흐름에서의 오염물질 이동에 대한 이차흐름의 영향을 분석하였다. 그 결과, 이차흐름의 영향으로 인해 최대 농도 값의 발생 위치가 이동하는 것으로 나타났으며, 농도 분포 역시 정규 분포에서 거리에 따라 점차 왜곡 되는 것으로 확인되었다. 또한, 이차흐름의 영향으로 자유수면 근처에서는 매끄러운 하상에 비해 거친 하상에서의 오염물질 농도가 더 크게 발생되었으며, 스칼라-흐름률을 계산한 결과, 오염물질의 수직방향 확산은 매끄러운 하상에 비해 거친 하상에서 더 빨리 진행되는 것으로 확인되었다. 한편, 농도 분포 변화에 대한 이차흐름 및 스칼라-흐름률의 영향을 살펴보기 위하여 스칼라 수송률 분석을 수행하였다.

Keywords

References

  1. Choi, S.-U. and Kang, H. (2008) Reynolds stress modeling of turbulent open-channel flows. in Water Resources Research Trend, Nova Science Publishing Inc., N.Y.
  2. Choi, S.-U., Park, M., and Kang, H. (2007) Numerical simulations of cellular secondary currents and suspended sediment transport in open-channel flows over smooth-rough bed strips. Journal of Hydraulic Research, IAHR, Vol. 45, No. 6, pp. 829-840. https://doi.org/10.1080/00221686.2007.9521820
  3. Daly, B.J. and Harlow, F.H. (1970) Transport equations in turbulence. Physics of Fluids, Vol. 13, pp. 2634-2649. https://doi.org/10.1063/1.1692845
  4. Kang, H. and Choi, S.-U. (2008) Scalar flux modeling of solute transport in open channel flows: numerical test and effect of secondary currents. Journal of Hydraulic Research, IAHR, submitted.
  5. Kearney, D.J. (2000) Turbulent diffusion in channels of complex geometry. Ph.D. thesis, Loughbough University. England.
  6. Launder, B.E. and Ying, W.H. (1973) Prediction of flow and heat transfer in ducts of square cross section. Proceedings of Instruction Mechanical Engineers, Vol. 187, pp. 455-461. https://doi.org/10.1243/PIME_PROC_1973_187_131_02
  7. Lin, B. and Shiono, K. (1995) Numerical modeling of solute transport in compound channel flows. Journal of Hydraulic Research, IAHR, Vol. 33, No. 6, pp. 773-788. https://doi.org/10.1080/00221689509498551
  8. McLean, S.R. (1981) The role of non uniform roughness in the formation of sand ribbons. Marine Geology, Vol. 42, pp. 49-74. https://doi.org/10.1016/0025-3227(81)90158-4
  9. McLelland, S.J., Ashworth, P.J., Best, J.L., and Livesey, J.R. (1999) Turbulence and secondary flow over sediment strips in weakly bimodal bed material. Journal of Hydraulic Engineering, ASCE, Vol. 125, No. 5, pp. 463-473. https://doi.org/10.1061/(ASCE)0733-9429(1999)125:5(463)
  10. Muller, A. and Studerus, X. (1979) Secondary flow in an open-channel. Proc. of 18th IAHR congress, Cagliari, Vol. 3, pp. 19-24.
  11. Naot, D. (1984) Response of channel flow to roughness heterogeneity. Journal of Hydraulic Engineering, ASCE, Vol. 110, No. 11, pp. 1568-1587. https://doi.org/10.1061/(ASCE)0733-9429(1984)110:11(1568)
  12. Nezu, I. and Nakagawa, H. (1993) Turbulence in open-channel flows. Monograph, Balkema, Rotterdam, The Netherland.
  13. Nezu, I. and Nakagawa, H. (1984) Cellular secondary currents in straight conduit. Journal of Hydraulic Engineering, ASCE, Vol. 110, No. 2, pp. 173-193. https://doi.org/10.1061/(ASCE)0733-9429(1984)110:2(173)
  14. Ohmoto, T. and Hayashi, S. (2003) Study of generation mechanism of secondary currents in open-channel flow by direct numerical simulation. Journal of Hydroscience and Hydraulic Engineering, Vol. 21, No. 1, pp. 11-21.
  15. Prinos, P. (1992) Dispersion in compound open channel flow. Hydraulic and Environmental Modeling: Estuarine and River Waters, Ed. Falconer, Shiono, Mattew, Ashgate Publishng Ltd., pp. 359-372.
  16. Simoes, F.J.M. and Wang, S.S.Y. (1997) Numerical prediction of three dimensional mixing in a compound channel. Journal of Hydraulic Research, IAHR, Vol. 35, No. 5, pp. 619-642. https://doi.org/10.1080/00221689709498398
  17. Shiono, K., Scott, C.F., and Kearney, D. (2003) Predictions of solute transport in compound channel using turbulence models. Journal of Hydraulic Research, IAHR, Vol. 41, No. 3, pp. 247-258. https://doi.org/10.1080/00221680309499970
  18. Wang, Z.-Q. and Cheng, N.-S. (2005) Secondary flows over artificial bed strips. Advances in Water Resources, Vol. 28, pp. 441-450. https://doi.org/10.1016/j.advwatres.2004.12.008