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A multiphase flow modeling of gravity currents in a rectangular channel

사각형 수로에서 중력류의 다상흐름 수치모의

  • Kim, Byungjoo (Department of Civil Engineering, Gangnueng-Wonju National University) ;
  • Paik, Joongcheol (Department of Civil Engineering, Gangnueng-Wonju National University)
  • 김병주 (강릉원주대학교 공과대학 토목공학과) ;
  • 백중철 (강릉원주대학교 공과대학 토목공학과)
  • Received : 2019.07.31
  • Accepted : 2019.09.26
  • Published : 2019.10.31

Abstract

A multiphase flow modeling approach equipped with a hybrid turbulence modeling method is applied to compute the gravity currents in a rectangular channel. The present multiphase solver considers the dense fluid, the less-dense ambient fluid and the air above free surface as three phases with separate flow equations for each phase. The turbulent effect is simulated by the IDDES (improved delayed detach eddy simulation), a hybrid RANS/LES, approach which resolves the turbulent flow away from the wall in the LES mode and models the near wall flow in RANS mode on moderately fine computational meshes. The numerical results show that the present model can successfully reproduce the gravity currents in terms of the propagation speed of the current heads and the emergence of large-scale Kelvin-Helmholtz type interfacial billows and their three dimensional break down into smaller turbulent structures, even on the relatively coarse mesh for wall-modeled RANS computation with low-Reynolds number turbulence model. The present solutions reveal that the modeling approach can capture the large-scale three dimensional behaviors of gravity current head accompanied by the lobe-and-cleft instability at affordable computational resources, which is comparable to the LES results obtained on much fine meshes. It demonstrates that the multiphase modeling method using the hybrid turbulence model can be a promising engineering solver for predicting the physical behaviors of gravity currents in natural environmental configurations.

다상흐름 모델링 기법과 하이브리드 난류 모델링 기법을 결합한 수치모형을 이용하여 사각형 수로에서의 중력류를 수치모의 하였다. 이 연구에서 적용한 다상흐름 해석기법은 밀도가 큰 중력류 유체, 상대적으로 밀도가 작은 주변류 유체 그리고 자유수면 위에서 흐르는 공기를 3개의 상으로 처리하며, 각 상에 대해서 분리된 흐름 지배방정식을 적용한다. 난류흐름은 벽경계 근처에서는 RANS 모드로 모의하고 벽에서 떨어진 영역에서는 LES 모드로 해석하는 하이브리드 RANS/LES 방법의 일종인 IDDES 기법을 이용하여 해석한다. 이 연구에서 적용한 모델링 기법은 중력류의 머리의 전파속도를 실험값과 일치하게 잘 예측하는 것으로 나타났다. 수치해석 결과는 아울러 낮은 레이놀즈수 난류모형을 이용한 RANS 수치모의에서 이용되는 정도의 격자해상도에서도 큰 규모의 Kelvin-Helmholtz 형식의 경계면 와의 발달과 이들 와가 지속적으로 3차원 형식의 붕괴를 거쳐 작은 난류구조로 분해되면서 난류에너지가 소산되는 현상을 성공적으로 예측함을 보여준다. 적용한 수치모의 기법은 공학적으로 접근 가능한 격자해상도에서 돌출-쪼개짐 흐름 불안정을 동반한 중력류 머리부분의 3차원 거동 특성을 잘 재현하며, 이 결과는 보다 높은 격자해상도에서 구해진 LES 결과에 상응하는 것으로 나타났다. 이 연구결과는 하이브리드 난류모델링 기법과 다상흐름 해석기법을 병합한 수치모형이 자연상태에서 복잡한 중력류의 물리적 거동을 예측하는데 공학적으로 유망한 방법임을 보여준다.

Keywords

References

  1. Benjamin, T. B. (1968). "Gravity currents and related phenomena." Journal of Fluid Mechanics, Vol. 31, No. 2, pp. 209-248. https://doi.org/10.1017/S0022112068000133
  2. Bournet, P. E., Dartus, D., Tassin, B., and Vincon-Leite, B. (1999). "Numerical investigation of plunging density current." Journal of Hydraulic Engineering, Vol. 125, No. 6, pp. 584-594. https://doi.org/10.1061/(ASCE)0733-9429(1999)125:6(584)
  3. Britter R. E., and Simpson, J. E. (1981). "A note on the structure of the head of an intrusive gravity currents." Journal of Fluid Mechanics, Vol. 112, pp. 459-466. https://doi.org/10.1017/S0022112081000517
  4. Cantero, M. I., Lee, J. R., Balachandar, S., and Garcia, M. H. (2007). "On the front velocity of gravity currents." Journal of Fluid Mechanics, Vol. 586, pp. 1-39. https://doi.org/10.1017/S0022112007005769
  5. Choi, S., and Garcia, M. H. (2002). "k-${\varepsilon}$ turbulence modeling of density currents developing two dimensionally on a slope." Journal of Hydraulic Engineering, Vol. 128, No. 1, pp. 55-63. https://doi.org/10.1061/(ASCE)0733-9429(2002)128:1(55)
  6. Choi, S.-U., Kang, H., Yu, K., Paik, J., and Lee, S.-O. (2017). Hydraulics of turbulent flows, CIR.
  7. Dai, A. (2013). "Experiments on gravity currents propagating on different bottom slopes." Journal of Fluid Mechanics, Vol. 731, pp. 117-141. https://doi.org/10.1017/jfm.2013.372
  8. Eidsvik, K. J., and Brors, B. (1989). "Self-accelerated turbidity current prediction based upon k-${\varepsilon}$ model turbulence." Continental Shelf Research, Vol. 9, pp. 617-627. https://doi.org/10.1016/0278-4343(89)90033-2
  9. Gritskevich, M. S., Garbaruk, A. V., Schutze, J., and Menter, F. R. (2012). "Development of DDES and IDDES formulations for k-${\omega}$ the shear stress transport model." Flow Turbulence and Combustion, Vol. 88, No. 3, pp. 431-449. https://doi.org/10.1007/s10494-011-9378-4
  10. Hacker, J., Linden, P. F., and Dalziel, S. B. (1996). "Mixing in lock-release gravity currents." Dynamics of Atmospheres and Oceans, Vol. 24, No. 1-4, pp. 183-195. https://doi.org/10.1016/0377-0265(95)00443-2
  11. Hallworth, M. A., Huppert, H. E., Phillips, J. C., and Sparks, R. S. J. (1996). "Entrainment into two-dimensional and axisymmetric turbulent gravity currents." Journal of Fluid Mechanics, Vol. 308, pp. 289-311. https://doi.org/10.1017/S0022112096001486
  12. Hartel, C., Meiburg, E., and Necker, F. (2000). "Analysis and direct numerical simulation of the flow at a gravity-current head. Part 1. Flow topology and front speed for slip and no-slip boundaries." Journal of Fluid Mechanics, Vol. 418, pp. 189-212. https://doi.org/10.1017/S0022112000001221
  13. Huang, H., Imran, J., and Pirmez, C. (2005). "Numerical model of turbidity currents with a deforming bottom boundary." Journal of Hydraulic Engineering, Vol. 131, No. 4, pp. 283-293. https://doi.org/10.1061/(ASCE)0733-9429(2005)131:4(283)
  14. Huppert, H. E. (2006). "Gravity currents: a personal perspective." Journal of Fluid Mechanics, Vol. 554, pp. 299-322. https://doi.org/10.1017/S002211200600930X
  15. Inghilesi, R., Adduce, C., Lombardi, V., and Roman, F. (2018). "Axisymmetric three-dimensional gravity currents generated by lock exchange." Journal of Fluid Mechanics, Vol. 851, pp. 507-544. https://doi.org/10.1017/jfm.2018.500
  16. Klemp, J. B., Rotunno, R. and Skamarock, W. C. (1994). "On the dynamics of gravity currents in a channel." Journal of Fluid Mechanics, Vol. 269, pp. 169-198. https://doi.org/10.1017/S0022112094001527
  17. Lee, W. D., and Hur, D.-S. (2014). "Development of 3-D hydrodynamical model for understanding numerical analysis of density current due to salinity and temperature and its verification." Journal of the Korean Society of Civil Engineers, KSCE, Vol. 34, No. 3, pp. 859-871. https://doi.org/10.12652/Ksce.2014.34.3.0859
  18. Lee, W. D., Mizutani, N., and Hur, D. S. (2018). "Behavior characteristics of density currents due to salinity differences in a 2-d water tank." Journal of Ocean Engineering and Technology, Vol. 32, No. 4, pp. 261-271. https://doi.org/10.26748/KSOE.2018.6.32.4.261
  19. Maxworthy, T., and Nokes, R. I. (2007). "Experiments on gravity currents propagating down slopes. Part 1. The release of a fixed volume of heavy fluid from an enclosed lock into an open channel." Journal of Fluid Mechanics, Vol. 584, pp. 433-453. https://doi.org/10.1017/S0022112007006702
  20. Menter, F. R. (1994). "Two-equation eddy-viscosity turbulence models for engineering applications." AIAA Journal, Vol. 32, No. 8, pp. 1598-1605. https://doi.org/10.2514/3.12149
  21. Nasr-Azadani, M. M., and Meiburg, E. (2014). "Turbidity currents interacting with three-dimensional seafloor topography." Journal of Fluid Mechanics, Vol. 745, pp. 409-443. https://doi.org/10.1017/jfm.2014.47
  22. Ooi, S. K., Constantinescu, G., and Weber, L. J. (2006). Numerical simulation of lock-exchange gravity driven flows. IIHR Technical Rep., No. 450, University of Iowa, Iowa City, Iowa.
  23. OpenFOAM (2018). OpenFOAM - The open source CFD toolbox 1812 User's Guide.
  24. Paik, J., Eghbalzadeh, A., and Sotiropoulos, F. (2009) "Three-dimensional unsteady RANS modeling of discontinuous gravity currents in rectangular domains." ASCE Journal of Hydraulic Engineering, Vol. 135, No. 6, pp. 505-521. https://doi.org/10.1061/(ASCE)HY.1943-7900.0000034
  25. Patterson, M. D., Simpson, J. E., Dalziel, S. B., and van Heijst, G. J. F. (2006). "Vortical motion in the head of an axisymmetric gravity current." Physics of Fluids, Vol. 18, p .046601. https://doi.org/10.1063/1.2174717
  26. Schiller, L., and Nauman, A. (1935). "A drag coefficient correlation." VDI Zeitung, Vol. 77, pp. 318-320.
  27. Shur, M. L., Spalart, P. R., Stretlets, M. K., and Travin, A. K. (2008). "A hybrid RANS-LES approach with delatyed-DES and wall-modelled LES capabilities." International Journal of Heat and Fluid Flow, Vol. 29, No. 6, pp. 1638-1649. https://doi.org/10.1016/j.ijheatfluidflow.2008.07.001
  28. Simpson, J. E. (1997). Gravity currents in the environment and the laboratory, 2nd ed. Cambridge University Press, New York.
  29. Spalart, P. R., and Allmaras, S. R. (1994). "A one-equation turbulence model for aerodynamic flows." La Rech. Aerospatiale, Vol. 1, pp. 5-21.
  30. Spalart, P. R., Deck, S., Shur, M. L., Squires, K. D., Strelets, M. K., and Travin, A. (2006). "A new version of detached-eddy simulation, resistant to ambiguous grid densities." Theoretical and Computational Fluid Dynamics, Vol. 20, pp. 181-195. https://doi.org/10.1007/s00162-006-0015-0
  31. Steenhauer, K., Rokyay, T., and Constantinescu, G. (2017). "Dynamics and structure of planar gravity currents propagating down on inclined surface." Physics of Fluids, Vol. 29, No. 3, p. 036604. https://doi.org/10.1063/1.4979063
  32. Strelets, M. (2001). "Detached eddy simulation of massively separated flow." AIAA Journal, pp. 1-18.
  33. Sutherland, B. R., Kyba, P. J., and Flynn, M. R. (2004) "Intrusive gravity currents in two-layer fluids." Journal of Fluid Mechanics, Vol. 514, pp. 327-353. https://doi.org/10.1017/S0022112004000394
  34. Ungarish, M. (2007). "A shallow-water model for high-Reynolds-number gravity currents for a wide range of density differences and fractional depths." Journal of Fluid Mechanics, Vol. 579, pp. 373-382. https://doi.org/10.1017/S0022112007005484
  35. Zgheib, N., Ooi, A., and Balachandar, S. (2016). "Front dynamics and entranment fo finite curcular gravity currents on a unbounded uniform slope." Journal of Fluid Mechanics, Vol. 801, pp. 322-352. https://doi.org/10.1017/jfm.2016.325