Numerical Simulation of Cavitation and Aeration in Discharge Gated Tunnel of a Dam Based on the VOF Method

Cavitation, usually known as a destructive phenomenon, involves turbulent unsteady two-phase flow. Having such features, cavitating flows have been turned to a challenging topic in numerical studies and many researches are being done for better understanding of bubbly flows and proposing solutions to reduce its consequent destructive effects. Aeration may be regarded as an effective protection against cavitation erosion in many hydraulic structures, like gated tunnels. The paper concerns numerical simulation of flow in discharge gated tunnel of a dam using ing RNG k -ε model coupled with the volume of fluid (VOF) method and the zone which is susceptible of cavitation inception in the tunnel is predicted. In the second step, a vent is considered in the mentioned zone for aeration and the numerical simulation is done again to study the effects of aeration. The results show that aeration is an impressively useful method to exclude cavitation in mentioned tunnels.

Authors:

• Razieh Jalalabadi
• Norouz Mohammad Nouri

Keywords:

• Aeration
• Cavitation
• Two-phase flow
• TurbulentFlow
• Volume of Fluid (VOF) method.

References:

[1] S. Bernard, S. Muntean, R.F. Susan-Resiga, I. Anton, "Multiphase
Modeling of Cavitating Flows", Buletinul ┼×tiintific AL Universitatii
"POLITEHNICA" Din Timisoara, Transactions on Mechanics, 2004.
[2] S. Bernad, R. Susa-Resiga, S. Muntean, I. Anton, "Numerical Analysis
Of The Cavitating Flows", In Proceedings of The Romanian Academy,
Series A, vol. 7, no.1, 2006.
[3] Y. Xiong, Y. Gao, W. An, "Comparison of Turbulence Models in
Predicting Unsteady Supercavitating Flow", Sixth International
Symposium on Cavitation, CAV2006, Netherlands, 2006.
[4] F.R. Young, " Cavitation ", 1st ed, Imperial College press, 1999.
[5] FLUENT 6. User-s Guide, Fluent Incorporated, 2003.
[6] C.W. Hirt, B.D. Nichols., "Volume of Fluid (VOF) Method for the
Dynamics of Free Boundaries", Journal of Computational Physics, vol.
39, pp. 201-225, 1981.
[7] S.H. Rhee, B.P. Makarov, H. Krishinan, V. Ivanov, "Assessment of the
Volume of Fluid Method for Free-Surface Wave Flow", Journal of
Marine Science and Technology, vol. 10, pp. 173-180, 2005.
[8] M. R. Najafi, A. R. Zarrati, "Numerical simulation of air-water flow in
gated tunnels", Proceedings of the ICE - Water Management, vol. 163,
Issue 6, pp. 289 -295, 2010.
[9] M. Toorani, "An Investigation of Air Injection effect on Pressure
Changes in Super Critical Flows", Bachelor Thesis, K.N. Toosi
University of Technology, Civil Engineering Department, 2004.
[10] G. E. Reisman, M. E. Duttweiler, and C. E. Brennen, "Effects of Air
Injection on the Cloud Cavitation of a Hydrofoil", ASME Fluids
Engineering Division Summer Meeting, FEDSM'97, June, 1997.
[11] Jahed Motlagh, H.R., Noban, M.R., Eshraghi, M.A., Ansys, 1st Ed,
IUST Press,Tehran, pp. 285-297, 2002.
[12] X. Wang, X. Wang, C. Wang, J. An, Z. Zhang, Q. Duan, "Numerical
Simulation of Long-Distance Diversion Tunnel with Free Flow Based on
the VOF Method", Proceedings of International Symposium on
Information Science and Engineering, vol. 1, pp. 19-23, 2008.
[13] H. Tang, L.C. Wrobel, Z. Fan, "Tracking of Immiscible Interface in
Multiple-Material Mixing Process", Comput. Materials Science, vol. 29,
pp 103-118, 2004.
[14] V. Yakhot, S.A. Orszag, "Renormalization-Group Analysis of
Turbulence, Journal of Scientific Computing", vol. 1, no. 1, pp. 3-51,
1986.
[15] C. Xiangju, C. Yongcan, L. Lin, "Numerical simulation of air-water
two-phase flow over stepped spillways", Science in China Series E:
Technological Sciences, vol. 49, no. 6, pp. 674-684, 2006.
[16] A., Mohaghegh, J. H. WU, "Effects of hydraulic and geometric
parameters on downstream cavity length of discharge tunnel service
gate", Journal of Hydrodynamics, Ser. B, vol. 21, Issue 6, pp. 774-778,
2009.