Study of Two-Phase Flow Behavior around Chute Aerator Using OpenFOAM

Hamzeh Ebrahimnezhadian, Mohammad Manafpour

Abstract


Aeration devices are installed on chute spillways to prevent cavitation damage in high-velocity flows. Large quantities of air-entrained characterize bottom aerators along with the jet interfaces and a strong de-aeration process near the impact of the water jet with the spillway bottom. Appropriate prediction of the air entrainment process, flow characteristics, and two-phase flow pattern at the aerator would contribute to reliable spillway operation. The mathematical formulation of two-phase flow at an aerator remains a challenging issue for spillway design due to its complexities. In the present study, 2D numerical simulations are performed to predict the distribution of air concentrations, flow velocity, turbulent intensity, and water surface profile along the chute aerator using open-source OpenFOAM software and RNG k-ε turbulent model. The correlation coefficients obtained between the numerical and experimental results indicate that a proper agreement exists between the relative cavity length and velocity profile results. The research results show that the turbulent intensity of flow passing over the aerator ramp is significantly increases. It means that the ramp acts as a turbulent generator on the spillway chute. The maximum value of turbulence intensity occurs at the 6-8% of flow depth(h) from the tip of the ramp, and it is raised as the Froude number increases. It is concluded that the intake air flow rate and air-entrainment coefficient (𝛽) are linearly increased concerning the Froude number.

Keywords


Aerator ramp; air entrainment; cavity length; RNG k-ε turbulence model; OpenFOAM

Full Text:

PDF

References


H. Falvey, “Cavitation in Chutes and Spillways” Engineering Monograph 42, United States Department of the Interior, Bureau of Reclamation, Denver, Colo, USA. 1990.

J. A. Kells, and C. D. Smith, “Reduction of cavitation on spillways by induced air entrainment” Canadian Journal of Civil Engineering., Vol 18, pp. 358–377, 1991.

N. L. Pinto, “Prototype aerator measurements” IAHR Hydraulic Structures Design Manual No. 4, Ed. I.R, 1991.

W. Wei, J, Deng, and Z. Faxing “Development of self-aeration process for supercritical chute flows” International Journal of Multiphase Flow, Vol 79, pp. 172–180, 2016.

A. J. Peterka, “The effect of entrained air on cavitation pitting” Joint Meeting Paper, IAHR/ASCE, Minneapolis, Minnesota, pp. 507-518, Aug. 1953.

J. M. Zhang, J. G. Chen, and W. L. Xu, “Three-dimensional numerical simulation of aerated flows downstream sudden fall aerator expansion in a tunnel” Journal of Hydrodynamics, Vol 23(1), pp. 71–80, 2011.

R.W.P. May, P. M. Brown, and I. R. Willoughby, “Physical and numerical modeling of aerators for dam spillways” Hydraulics Research Report, No. SR 278, Wallingford, U.K. 1991.

D. Vischer, , P. Volkart, and A. Sigenthaler, “Hydraulic modelling of air slots in open chute spillways” International Conference on the Hydraulic Modelling of Civil Engineering Structures, 1982, Coventry, U.K., pp. 22–24.

J. Yang, P. Teng, and H. Zhang, “Experiments and CFD modeling of high-velocity two-phase flows in a large chute aerator facility” Journal of Engineering Applications of Computational Fluid Mechanics, Vol 13(1), pp. 48-66, 2018.

H. Chanson, “Study of Air Entrainment and Aeration Devices” Journal of Hyd. Research, IAHR, Vol 27 (3), pp. 301-319, 1989a.

H. Chanson, “Aeration of a free jet above a spillway” Journal of Hyd. Res., IAHR, Vol 29(6), p. 864, 1991.

I. Schwartz, and L. P. Nutt, “Projected nappes subjected to transverse pressure” Journal of the Hydraulics Division, Vol 89(7), pp. 97–104,1963.

S. b. Pan, , Y. y. Shao, Q. s. Shi, and X. l. Dong, “Selfaeration capacity of a water jet over an aeration ramp” Shuili Xuebao Journal of Hydraulic Engineering, Beijing, Vol 5, pp.13–22, 1980.

K. Kramer, and W. H. Hager, “Air transport in chute flows” International Journal of Multiphase Flow, Vol 31(10-11), pp. 1181–1197, 2005.

M. C. Aydin, and M. Ozturk, “Verification and validation of a computational fluid dynamics (CFD) model for air entrainment at spillway aerators” Canadian Journal of Civil Engineering, Vol 36(5), pp.826–836, 2010.

H. W. Zhang, Z. P. Liu, D. Zhang, and Y. H. Wu, “Numerical simulation of aerated high velocity flow downstream of an aerator,” Journal of Hydraulic Engineering, Vol 39(12), pp. 1302–1308, 2008.

B. Ruidi, Z. Faxing, and L. Shanjun, “Air concentration and bubble characteristics downstream of a chute aerator” International Journal of Multiphase Flow, Vol 87, pp. 156–166, 2016.

P. Teng, J. Yang, and P. L. Ligier, “Air Demand Due to Flood Discharges at MOFORSEN dam ‒ CFD Modelling with Field Measurments” E-proceedings of the 2nd International Symposium on Hydraulic Modelling and Measuring Technology, 2018, Nanjing, China, pp. 68–76.

J. Lian, C. Qi, F. Liu, W. Gou, S. Pan and Q. Ouyang, “Air Entrainment and Air Demand in the Spillway Tunnel at the Jinping-I Dam” Journal of Applied Sciences, Vol 7, pp. 89–112, 2017.

J. Yang, P. Teng, and C. Lin, “Air-vent layouts and water-air flow behaviors of a wide spillway aerator” Journal of Theoretical & Applied Mechanics Letters, Vol 9, pp. 130–143, 2019.

J. Yang, P. Teng, and Q. Xie, “Modelling of Air Demand of Spillway Aerators with Two-Phase Flow Model” E-proceedings of the 2nd International Symposium on Hydraulic Modelling and Measuring Technology, 2018, Nanjing, China, pp. 150–159.

P. Teng, J. Yang, and M. Pfister, “Studies of Two-Phase Flow at a Chute Aerator with Experiments and CFD Modelling” Journal of Modelling and Simulation in Engineering” Vol 8, pp. 100–111, 2016.

B. Ruidi, S. Liu, Z. Tian, and Z. Faxing, “Experimental investigation of bubbly fow and air entrainment discharge downstream of chute aerators” Journal of Environmental Fluid Mechanics, Vol 19, pp. 1455–1468, 2019.

M. K. Sarvar, L. Ahmad, Z. A. Chaudary, and H. R. Mughal, “Experimental and numerical studies on orifice spillway aerator of Bunji Dam” Journal of the Chinese institute of engineering, Vol 6, pp. 68–79, 2019.

J. Yang, P. Teng, and H. Zhang, “Experiments and CFD modeling of high-velocity two-phase flows in a large chute aerator facility” Journal of Engineering Applications of Computational Fluid Mechanics, Vol 13(1), pp. 48–66, 2018.

M. C. Aydin, “Aeration efficiency of bottom-inlet aerators for spillways” Journal of ISH Journal of Hydraulic Engineering, Vol 7, pp. 124–136, 2017.

M. C. Aydin, E, Isik, and A. Emre Ulu “Numerical modeling of spillway aerators in high head dams” Journal of ISH Journal of Applied Water Science, Vol 10, pp. 178–188, 2020.

A. C. M. LIMA, “Caracterização da estrutura turbulenta em escoamentos aerados em canal de forte declividade com auxílio de técnicas de velocimetria a laser,” Ph.D. dissertation, Escola de Engenharia, Universidade de São Paulo, São Carlos, Brasil, 2004.

OpenCFD Limited, “OpenFoam User Guide” 1.7.1 edition, 2016.

J. Tu, G. H. Yeoh, and C. Liu “Computational Fluid Dynamics” Springer, 3rd edition, 2019.




DOI: http://dx.doi.org/10.18517/ijaseit.11.4.10197

Refbacks

  • There are currently no refbacks.



Published by INSIGHT - Indonesian Society for Knowledge and Human Development