Journal of Korea Water Resources Association (한국수자원학회논문집)

Korea Water Resources Association (한국수자원학회)
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Evaluation of the applicability of a buoyancy-modified turbulence model for free surface flow analysis based on the VOF method

VOF 기반 자유수면 흐름 해석을 위한 부력 수정 난류 모형의 적용성 평가

  • Lee, Du Hana (Department of Hydro Science and Engineering Research, Korea Institute of Civll Engineering and Building Technology)
  • 이두한 (한국건설기술연구원 수자원하천연구본부)
  • Received : 2024.05.17
  • Accepted : 2024.07.05
  • Published : 2024.08.31
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Abstract

RANS-based CFD analysis is widely applied in various engineering fields, including practical hydraulic engineering, due to its high computational efficiency. However, problems of non-physical behavior in the analysis of two phase flow, such as free surfaces, have long been raised. The two-equation turbulence models used in general RANS-based analysis were developed for single phase flow and simulate unrealistically high turbulence energy at the interface where there are abrupt changes in fluid density. To solve this issue, one of the methods recently developed is the buoyancy-modified turbulence model, which has been partially validated in coastal engineering, but has not been applied to open channel flows. In this study, the applicability of the buoyancy-modified turbulence model is evaluated using the VOF method in the open-source program OpenFoam. The results of the uniform flow showed that both the buoyancy-modified k-𝜖 model and the buoyancy-modified k-ω SST model effectively simulated the reduction of turbulence energy near the free surface. Specifically, the buoyancy-modified k-ω SST model accurately simulated the vertical velocity distribution. Additionally, the model is applied to dam-break flows to examine cases with significant surface variation and cavity formation. The simulation results show that the buoyancy-modified turbulence models produce varying results depending on the VOF method and shows non-physical behavior different from experimental results. While the buoyancy-modified turbulence model is applicable in cases with stable surface shapes, it still has limitations in general application when there are rapid changes in the free surface. It is concluded that appropriate adjustments to the turbulence model are necessary for flows with rapid surface changes or cavity formation.

RANS 기반의 CFD 해석은 계산 효율성이 높아 실무 수리해석을 포함한 다양한 공학 분야에서 널리 적용되고 있으나 자유수면과 같이 이상유체흐름 해석에서 비물리적인 거동이 나타나는 문제가 오랫동안 제기되어 왔다. 일반적인 RANS 기반의 해석에서 적용되는 2 방정식 난류 모형은 단상유체를 대상으로 개발되어 유체 밀도의 급격한 변화가 발생하는 이상유체에서는 경계면에서 실제와 다른 높은 난류 에너지 생성을 모의한다. 최근 이를 해결하기 위해 개발된 방법 중의 하나인 부력 수정 난류 모형은 해안 분야에 적용되어 일부 적합성이 검증되었으나 개수로 흐름에 적용된 사례는 없다. 본 연구에서는 오픈 소스 프로그램인 OpenFoam의 VOF 기법을 기반으로 부력 수정 난류 모형의 적용성을 평가하였다. 등류 흐름 적용 결과에 의하면 부력 수정 k-𝜖 모형과 부력 수정 k-ω SST 모형이 자유수면 부근에서의 난류 에너지 저감 현상을 잘 모의함을 확인하였으며, 특히 부력 수정 k-ω SST 모형은 연직 유속 분포를 잘 모의함을 확인하였다. 또한 댐 붕괴 흐름에 적용하여 수면형의 변동이 크고 공동이 형성되는 경우에 대해 검토하였다. 모의 결과 부력 수정 난류 모형은 VOF 기법에 따라 상이한 결과를 나타내며 실험결과와 다른 비물리적인 거동을 나타내었다. 부력 수정 난류 모형이 수면이 안정적인 형태인 경우에는 적용성이 있으나 자유 수면의 급격한 변화가 발생하는 경우에 범용적으로 적용하기에는 여전히 한계가 있는 것으로 나타났다. 수면형이 급격하게 변화하거나 공동이 형성되는 흐름의 경우에는 난류 모형에 대한 적절한 보정이 필요한 것으로 판단된다.

Keywords

Acknowledgement

본 연구는 한국건설기술연구원 2024년도 목적형 목적형 R&R 사업 '기후위기 대응 물문제 해결형 이슈 발굴 및 미래선도 기술 개발(20240128-001)'의 일환으로 수행되었습니다.

References

  1. ANSYS Fluent (2016). ANSYS Fluent theory guide. PA, U.S.
  2. Bradford, S.F. (2000). "Numerical simulation of surf zone dynamics." Journal of Waterway, Port, Coastal, and Ocean Engineering, Vol. 126, No. 1, pp. 1-13. doi: 10.1061/(ASCE)0733-950X(2000)126:1(1).
  3. Brown, S.A., Greaves, D.M., Magar, V., and Conley, D.C. (2016). "Evaluation of turbulence closure models under spilling and plunging breakers in the surf zone." Coastal Engineering, Vol. 114, pp. 177-193. doi: 10.1016/j.coastaleng.2016.04.002.
  4. Christensen, E.D. (2006). "Large eddy simulation of spilling and plunging breakers." Coastal Engineering, Vol. 53, No. 5-6, pp. 463-485. doi: 10.1016/j.coastaleng.2005.11.001.
  5. Deshpande, S.S., Anumolu, L., and Trujillo, M.F. (2012). "Evaluating the performance of the two-phase flow solver interFoam." Computational Science & Discovery, IOP Publishing Ltd, Vol. 5, No. 1, 014016.
  6. Devolder, B., Troch, P., and Rauwoens, P. (2018). "Performance of a buoyancy-modified k-ω and k-ω SST turbulence model for simulating wave breaking under regular waves using Open-FOAM®." Coastal Engineering, Vol. 138, pp. 49-65. https://doi.org/10.1016/j.coastaleng.2018.04.011
  7. Egorov, Y., Boucker, M., Martin, A., Pigny, S., Scheuerer, M., and Willemsen, S. (2004). "Validation of CFD codes with PTS-relevant test cases." 5th Euratom Framework Programme ECORA Project 2004, pp. 91-116.
  8. Fernandez-Mora, A., Ribberink, J.S., van der Zanden, J., van der Werf, J.J., and Jacobsen, N.G. (2017). "RANS-VOF modeling of hydrodynamics and sand transport under full-scale nonbreaking and breaking waves." Proceedings of 35th Conference on Coastal Engineering, Antalya, Turkey, pp. 1-15. doi: 10.9753/ICCE.V35.SEDIMENT.29.
  9. Frederix, E.M.A., Mathur, A., Dovizio, D., Geurts, B.J., and Komen, E.M.J. (2018). "Reynolds-averaged modeling of turbulence damping near a large-scale interface in two-phase flow." Nuclear Engineering and Design, Vol. 333, pp. 122-130. doi: 10.1016/j.nucengdes.2018.04.010.
  10. Garoosi, F., Mellado-Cusicahua, A.N., Shademani, M., and Shakibaeinia, A. (2022). "Experimental and numerical investigations of dam break flow over dry and wet beds." International Journal of Mechanical Sciences, Vol. 215, 106946. doi: 10.1016/j.ijmecsci.2021.106946.
  11. Guo, J., Julien, P.Y., and Meroney, R.N. (2005). "Modified Log-wake law in Zero-pressure-gradient turbulent boundary layers." Journal of Hydraulic Research, IAHR, Vol. 43, No. 4, pp. 421-430. https://doi.org/10.1080/00221680509500138
  12. Hirt, C.W., and Nichols, B.D. (1981). "Volume of fluid (VoF) method for the dynamics of free boundaries." Journal of Computational Physics, Vol. 39, No. 1, pp. 201-225. doi: 10.1016/0021-9991(81)90145-5.
  13. Hoang, D.A., van Steijn, V., Portela, L.M., Kreutzer, M.T., Kleijn, C.R. (2013). "Benchmark numerical simulations of segmented two-phase flows in microchannels using the Volume of Fluid method." Computers & Fluids, Vol. 86, pp. 28-36. doi: 10.1016/j.compfluid.2013.06.024.
  14. Jacobsen, N.G., Fredsoe, J., and Jensen, J.H. (2014). "Formation and development of a breaker bar under regular waves. Part 1: Model description and hydrodynamics." Coastal Engineering, Vol. 88, pp. 182-193. doi: 10.1016/j.coastaleng.2013.12.008.
  15. Kamath, A., Gabor F., and Hans B. (2019). "Investigation of free surface turbulence damping in RANS simulations for complex free surface flows." Water, Vol. 11, No. 3, 456. doi: 10.3390/w11030456.
  16. Marschall, H., Hinterberger, K., Schuler, C., Habla, F., and Hinrichsen, O. (2012). "Numerical simulation of species transfer across fluid interfaces in free-surface flows using OpenFOAM." Chemical Engineering Science, Vol. 78, pp. 111-127. doi: 10.1016/j.ces.2012.02.034.
  17. Mayer, S., and Madsen, P.A. (2001). "Simulation of breaking waves in the surf zone using a Navier-Stokes solver." Coastal Engineering 2000, ASCE, Sydney, Australia, pp. 928-941. https://doi.org/10.1061/40549(276)72.
  18. 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
  19. Mukha, T., Almeland, S.K., and Bensow, R.E. (2022). "Large-eddy simulation of a classical hydraulic jump: Influence of modelling parameters on the predictive accuracy." Fluids 2022, Vol. 7, No. 3, 101.
  20. Nezu, I., and Rodi, W. (1986). "Open-channel flow measurements with a laser doppler anemometer." Journal of Hydraulic Engineering, Vol. 112, No. 5, pp. 335-355. https://doi.org/10.1061/(ASCE)0733-9429(1986)112:5(335)
  21. Raeini, A.Q., Blunt, M.J., and Bijeljic, B. (2012). "Modelling twophase flow in porous media at the pore scale using the volumeof- fluid method." Journal of Computational Physics, Vol. 231, No. 17, pp. 5653-5668, doi: 10.1016/j.jcp.2012.04.011.
  22. Roenby, J., Bredmose, H., and Jasak, H. (2016). "A computational method for sharp interface advection." Royal Society Open Science, Vol. 3, No. 11, 160405.
  23. Roenby, J., Larsen, B.E., Bredmose, H., and Jasak H. (2017). "A new volume-of-fluid method in OpenFOAM." VII International Conference on Computational Methods in Marine Engineering, Rome, Italy.
  24. Weller, H. (2008). A new approach to VOF-based interface capturing methods for incompressible and compressible flows. Report TR/HGW/04, OpenCFD Ltd., MA, U.S.
  25. Xie, Z. (2013). "Two-phase flow modelling of spilling and plunging breaking waves." Applied Mathematical Modelling, Vol. 37, No. 6, pp. 3698-3713. doi: 10.1016/j.apm.2012.07.057.
  26. Xie, Z., Lin, B., Falconer, R.A., Nichols, A., Tait, S.J., and Horoshenkov, K.V. (2022). "Large-eddy simulation of turbulent free surface flow over a gravel bed." Journal of Hydraulic Research, Vol. 60, No. 2, pp. 205-219. doi: 10.1080/00221686.2021.1908437.
  27. Zhou, Z., Hsu, T.J., Cox, D., Liu, X. (2017). "Large-eddy simulation of wave-breaking induced turbulent coherent structures and suspended sediment transport on a barred beach." Journal of Geophysical Research: Oceans, Vol. 122, No. 1, pp. 207-235. doi: 10.1002/2016JC011884.