Numerical simulation of the effect of waves on the vortex formed in the vertical intake

Document Type : Original Research

Authors
E. Pakdel 1
M. majdzadeh tabatabaie 2
H. Sarkarde 3
S. H. Ghoraishi Najafabadi 4
1 Master Student of Shahid Beheshti University
2 Assistant professor of Shahid Beheshti university
3 Assistant Professor of Hakim Sabzevari University
4 Assistant professor of Shahid Beheshti University
Abstract
The formation of a vortex at the mouth of power plant intake is one of the unfavorable hydraulic phenomena that occur during dewatering of dams. More precisely, the formation of vortex flows in the openings of the intake disturbs the proper functioning of the intake structure. vortices cause problems such as oscillating in the system, reducing turbine output, increasing hydraulic losses in the intake openings, entering the air and particles into the intake pipe and eventually reducing its efficiency. In recent years, various scholars have conducted extensive studies on the phenomenon of vortex. In the meantime, research has been carried out experimentally using mechanical devices and less attention has been paid to the natural phenomena existing on the level of reservoirs of dams and their impact on the vortex. One of the most important natural phenomena that occurs in the reservoir of dams is the waves that can affect the vortex. In this research, with the aim of investigating the effect of waves on the vortex, numerical simulation of waves in the openings of vertical intake has been studied in various vortex formation conditions. In this regard, three class of vortices A, B and C were simulated in numerical model and the results were investigated after dealing with waves. To simulate the flow in the vertical intake, the model designed by Sun and Liu was used. This model is designed in a cylindrical shape with four rectangular inlets, with a vertical intake located at the center and end of the cylinder. In the present study, the model was studied in three-dimensional and two-phase mode, so that numerical simulation of vortex and wave can be investigated with this approach. In order to reduce the computational time to solve the equations, Euler's method was chosen and the turbulence was simulated using the LES model in STAR-CCM Software. After sensitivity analysis, 3 mm grid dimensions were selected. For computational mesh domain, a Cartesian coordinate was used and the free surface was considered using the VOF method. Accordingly, after formation of three classes of vortices A, B and C in the numerical model, three waves with a/d ratio of 2.6%, 1.3% and 0.3% were generated and the effect of their collisions on vortices was analyzed. The amplitudes of the waves are determined in relative proportions of the reservoir water's height and are not far from reality. The results showed that the waves reduced the components of tangential, radial and axial velocity. According to the results, the maximum component of the tangential velocity at the time of the presence of waves is reduced by about 14%, 19% and 23%, respectively, in the class A, B, and C vortices. The radial velocity component is also reduced by about 9%, 13% and 18% for the A, B, and C vortices, respectively. The maximum axial velocity was also reduced to 26%, 13%, and 23% for class A, B, and C vortices, respectively. According to the simulation results, the decrease rate with decrease decreasing wave amplitude, which means that smaller waves can lower the velocity components and thus weaken the vortex flow.

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[1] Knauss, J. 1978. Prediction of critical submergence, swirling flow problems at intakes, IAHR Hydraulic Structures Design Manual, 1, 7-11, Netherlands: Balkema Rotterdam.
[2] Rankine, W. J. M. 1858. A Manual of Applied Mechanics, London: R. Griffen.
[3] Kundu, P. 2002. Fluid Mechanics. Academic Press.
[4] Khadem rabe, B. 2017. Numerical and experimental study of air-core vortex in inclined intakes of power plant, PhD Thesis, Department of Water Resources Engineering, Shahid Beheshti University, Tehran. (In Persian)
[5] Sarkardeh, H., Zarrati, A. R., & Roshan, R. 2010. Effect of intake head wall and trash rack on vortices, Journal of Hydraulic Research, 48(1), 108-112.
[6] Hite, J., & Mih, W. 1994. Velocity of Air-Core Vortices at Hydraulic Intakes, Journal of Hydraulic Engineering, 120(3), 284-297.
[7] Uchiyama, T., & Ishiguro, Y. 2016. Study of the interactions between rising air bubbles and vortex core of swirling water flow around vertical axis, Chemical Engineering Science (Elsevier), 142, 137-143.
[8] Wang, Y. K., Jiang, C. B., & Liang, D. F. 2010. Investigation of air-core vortex at hydraulic intakes, Journal of Hydrodynamics, 22(5), 696-701.
[9] Monshizadeh, M., Tahershamsi, A., Rahimzadeh, H., & Sarkardeh, H. 2017. Experimental investigation of dynamics of the air-core vortices and estimating the air entrainment rate at a horizontal intake, Modares Mechanical Engineering, 17(8), 59-67. (in Persian)
[10] Khanarmuei, M. R., Rahimzadeh, H., & Sarkardeh, H. 2014. Investigating the effect of intake withdrawal direction on critical submergence and strength of vortices, Modares Mechanical Engineering, 14(10), 35-42. (In Persian)
[11] Chen, Y., Wu, C., Wang, B., & Du, M. 2012. Three-dimensional Numerical Simulation of Vertical Vortex at Hydraulic Intake. 2012 International Conference on Modern Hydraulic Engineering, 55-60.
[12] Suerich Gulick, F., Gaskin, S. J., Villeneuve, M., Holder, G., & Parkinson, É. 2006. Experimental and Numerical Analysis of Free Surface Vortices at a Hydropower Intake, 7th Int. Conf. Hydroscience and Engineering (ICHE). Philadelphia, USA.
[13] Li, H. F., Chen, H. X., Ma, Z., & Zhou, Y. 2008. Experimental and Numerical Envestigation of Free Surface Vortex, Journal of hydrodynamics, 20(4), 485-491.
[14] Aybar, A. 2012. Computational Modeling of Free Surface Flow in Intake Structures Using Flow 3D Software, Turkey: M.Sc. Thesis in Civil Eng, Middle East Technical University.
[15] Lucino, C., Liscia, S., & Duró, G. 2010. Vortex Detection in Pump Sumps by Means of CFD. XXIV Latin American Cong. Hydraulics Punta Del Este. Uruguay.
[16] Sarkardeh, H., Zarrati, A. R., Jabbari, E., & Marosi, M. 2014. Numerical Simulation and Analysis of Flow in a Reservoir in the Presence of Vortex. Engineering Applications of Computational Fluid Mechanics, 8(4), 598–608.
[17] Bin, J., Xianwu, L., Roger, E. A., & Yulin, W. 2014. Numerical simulation of three dimensional cavitation shedding dynamics with special emphasis on cavitation–vortex interaction, Occean engineerind, 8, (4), 656–660.
[18] Khadem-Rabe, B., Ghoreishi-Najafi, S. H., & Sarkardeh, H. 2017. Numerical Simulation of Air-Core Vortex at Intake, Journal of Current Science, 112(11), 435-448.
[19] Khadem-Rabe, B., Ghoreishi-Najafi, S. H., & Sarkardeh, H. 2016. Numerical simulation of anti-vortex devices at water intakes, Journal of Water Management (ICE), 170(3), 1-12.
[20] Sarkardeh, H. 2017. Numerical calculation of air entrainment rates due to intake vortices, Journal of Meccanica, 52(15), 3629–3643.
[21] Overview, P. (n.d.). 2013. Simcenter STAR-CCM+ Product Overview.
[22] Hirt, C., & Nichols, B. 1981. Volume of fluid (VOF) method for the dynamics of free boundaries, Journal of Computational Physics, 39, 201-225.
[23] Hirt, C. W., & Sicilian, J. M. 1985. A porosity technique for the definition of obstacles in rectangular cell meshes, Proceedings of the 4th International Conference on Ship Hydrodynamics, National Academy of Science, Washington, DC, 1–19.
[24] Schneiderbauer, S., & Krieger, M. 2014. What do the Navier–Stokes equations mean?, European Journal of Physics, 35, 1-24.
[25] Anderson, J. D. 1996. Computational Fluid Dynamics, New York: McGraw-Hill.
[26] Ahn, S. H., Xiao, Y., Wang, Z., Zhou, X., & Luo, Y. 2017. Numerical prediction on the effect of free surface vortex on intake flow characteristics for tidal power station, Renewable Energy, 101, 617-628.
[27] Dean, R.G., & Dalrymple, R.A. 1984. Water Wave Mechanics for Engineers and Scientists, 2, 261-269, Prentice-Hall, Englewood CliVs, NJ: World Scintifice.
[28] Sun, H., & Liu, Y. 2015. Theoretical and experimental study on the vortex at hydraulic intakes. Journal of Hydraulic Research, 53(6), 787–796.
[29] Ning, D. Z., Zang, J., Liu, S. X., Taylor, R. E., Teng, B., & Taylor, P. H. 2009. Free-surface evolution and wave kinematics for nonlinear uni-directional focused wave groups. Ocean Engineering, 36, 1226-1243.
[30] Sarkardeh, H., Zarrati, A, R,. Jabbari, E,. & Tavakkoli, S. 2014. Velocity field in a reservoir in the presence of an air-core vortex, ICE. Proceedings of the Institution of Civil Engineers, 167, 356–364.
Modares Civil Engineering journal
Volume 19, Issue 5
November and December 2019
Pages 59-71