KSCE Journal of Civil and Environmental Engineering Research (대한토목학회논문집)

Korean Society of Civil Engeneers (대한토목학회)
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Evaluation of Effective Wall Roughness for 3D Computational Analysis of Open Channel Flow

개수로 흐름의 3차원 전산해석을 위한 유효 벽면거칠기 산정

  • 최준우 (한양대학교 토목공학과) ;
  • 백운일 (한양대학교 토목공학과) ;
  • 이상목 (극동건설(주) 토목기술팀) ;
  • 윤성범 (한양대학교 공학대학 토목.환경공학과)
  • Received : 2008.01.08
  • Accepted : 2008.09.01
  • Published : 2008.11.30
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Abstract

In a numerical simulation of open channel turbulent flows using RANS (Reynolds averaged Navier-Stokes) equations model equipped with VOF (Volume of Fluid) scheme, the determination of wall roughness for wall function was studied. The roughness constant, based on the law-of-the-wall for flow on rough walls, obtained by experimental works for pipe flows is employed in general wall functions. However, this constant of wall function is the function of Froude number in open channel flows. Thus, the wall roughness should be determined by taking into account the effect of Froude number. In addition, the wall roughness should be corresponding to Manning's roughness coefficient widely used for open channels. In this study, the relation between wall roughness height as an input condition and Manning's roughness coefficient was investigated, and an equation for effective wall roughness height considering the characteristics of numerical models was proposed as a function of Manning's roughness coefficient.

개수로의 난류흐름을 VOF(Volume of Fluid)기법을 채용한 RANS(Reynolds averaged Navier-Stokes) 방정식 모형을 사용하여 수치모의할 때 벽면함수의 거칠기를 산정하기 위해 고려해야 하는 점들을 연구하였다. 거친 벽면상의 흐름을 위한 벽면함수의 거칠기 상수(roughness constant)는 관수로 흐름의 실험을 통하여 얻어진 값을 사용한다. 그러나 개수로 흐름에서는 이 거칠기 상수가 Froude 수에 따라 변화하므로 이를 고려할 수 있어야 하며, 개수로에서 광범위하게 사용되는 Manning 조도계수에 상응하는 벽면 거칠기 높이(roughness height)를 산정하여 사용할 수 있어야 있다. 본 연구에서는 모형에 입력되는 벽면함수의 거칠기 높이와 Manning 조도계수 사이의 관계를 분석하였다. 이를 바탕으로 수치모형의 특성이 고려되고 Manning 조도계수의 함수로 표현되는 유효 거칠기 높이 산정식을 제안하였다.

Keywords

References

  1. Chow, V.T. (1959) Open-Channel Hydraulics. McGraw-Hill, New York, pp. 200-206.
  2. Darcy, H. and Bazin, H. (1865) Recherches hydrauliques I, Recherches experimentales sur l'écoulement de l'eau dans les canaux découverts (Hydraulic research I, Experimetnal research on the flow of water in open channels), Memoires presentes par divers savants a l'Academie des Sciences, Vol. 19, No. 1, Dunod, Paris.
  3. Flow Science, Inc. (2000) FLOW-3D User Manual.
  4. FLUENT Inc. (2003) FLUENT 6.1 User's Guide.
  5. Iwagaki, Y. (1953) On the laws of rsistance to turbulent flow in open channels, Memoirs of the Faculty of Engineering, Kyoto University, Japan, Vol. 15, No. 1, pp. 27-40.
  6. Keulegan, G.H. (1938) Laws of turbulent flow in open channels, Research Paper RP 1151, Journal of Research, U.S. National Bureau of Stanards, Vol. 21. pp. 707-741. https://doi.org/10.6028/jres.021.039
  7. Millikan, C.B. (1938) A critical discussion of turbulent flows in channels and circular tubes. In J. P. Den Hartog and H. Peters (Eds.), Proc. 5th Int. Congress Applied Mechanics, Wiley, New York, pp. 386-392.
  8. Nikuradse, J. (1933) Strömungsgesetze in rauhen Röhren (Laws of flow in rough pipes), Verein deutscher Ingenieure, Forschungsheft No 361, Berlin.
  9. Pope, S.B. (2000) Turbulent flows. Cambridge University Press. pp. 290-298.
  10. Schlichting, H. (1979) Boundary Layer Theory (7th ed.). McGraw-Hill, New York.
  11. Strickler, A. (1923) Beitrage zur Frage der Geschwindigkeitsformel und der Rauhigkeitszahlen für Strome, Kanäle und geschlossene Leitungen. Mitteilungen des eidgenossischen Amtes fur Wasserwirtschaft, 16, Bern.
  12. Yakhot, V. and Orszag, S.A. (1986) Renormalization group analysis of turbulence. : Basic Theory, J. Sci. Comput., Vol. 1, No. 1, pp. 1-51.