Investigation on flow air concentration effect on distance of the chute spillway aerators

Document Type : Research Article

Authors

Department of Civil Engineering, University of Sistan and Baluchestan, Zahedan- Iran

Abstract

Flow aeration using aeration systems has been used as one of the most effective methods to prevent the occurrence of cavitation. Today, access to equipped computers and software based on computational fluid dynamics caused increasing use of numerical simulations in current analysis. In this research, Flow-3D software was used to simulate flow through the spillway aerator of chute. To validate the results of a numerical model in which the criterion was the air concentration in the aerator downstream, laboratory data of other researchers are used and the results indicate that they are in good agreement with the laboratory data. The effect of geometric parameters on the changes in air concentration, flow characteristics such as velocity and pressure to determine the cavitation index in order to determine distance between two aerators were explained. The average air concentration is as layer changes in the depth of flow and the reduction of air concentration is as exponential function. The value of the cavitation index is greater than the critical value within 11 meters after aerator in the chute spillway and there is no risk of cavitation occurrence. Considering the calculated concentrations, it can generally be concluded that by decreasing the air concentration in the chute bed to the values of 0.0001, 0.001, 0.01 and 0.1, chutes with slopes of 10, 12, 30 and 50 degrees do not require more aeration, respectively.

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References

[1] H.T. Falvey, Cavitation in chutes and spillways, US Department of the Interior, Bureau of Reclamation Denver, Colorado, 1990.
[2] R. Bai, S. Liu, Z. Tian, W. Wang, F. Zhang, Experimental Investigation of Air–Water Flow Properties of Offset Aerators, Journal of Hydraulic Engineering, 144(2) (2017) 1-10.
[3] H. Kobus, Introduction to air-water flows, in, Routledge, Germany, 1991, pp. 1-28.
[4] P. Rutschmann, Belüftungseinbauten in Schussrinnen, in, ETH,Zurich_in German, Mitteilung,97,D.Vischer,ed., Laboratory of Hydraulics ,Hydrology and Glaciology VAW, 1988.
[5] H. Chanson, A study of air entrainment and aeration devices on a spillway model, Ph.D. thesis, Univ. of Canterbury, Christchurch, 1988.
[6] P. Rutschmann, W.H. Hager, Air entrainment by spillway aerators, Journal of Hydraulic Engineering, 116(6) (1990) 765-782.
[7] M.A. Kökpınar, M. Göğüş, High-speed jet flows over spillway aerators, Canadian Journal of Civil Engineering, 29(6) (2002) 885-898.
[8] H. Chanson, Flow downstream of an aerator-aerator spacing, Journal of Hydraulic Research 27(4) (1989a) 519-536.
[9] M. Pfister, W. Hager, Chute aerators. I: Air transport characteristics, Journal of Hydraulic Engineering, 136(6) (2010) 352-359.
[10] M. Pfister, W. Hager, Chute aerators. II: Hydraulic design, Journal of Hydraulic Engineering 136(6) (2010) 360-367.
[11] M. Pfister, Chute Aerators: Steep deflectors and cavity subpressure, Journal of hydraulic engineering 137(10) (2011) 1208-1215.
[12] M.C. Aydin, Aeration efficiency of bottom-inlet aerators for spillways, ISH Journal of Hydraulic Engineering 24 (2017) 1-8.
[13] R. Bai, S. Liu, Z. Tian, W. Wang, F. Zhang, Experimental investigation of bubbly flow and air entrainment discharge downstream of chute aerators, Environmental Fluid Mechanics, 19(6) (2019) 1455-1468.
[14] M. Arami, Investigation of aeration on flow overflow, Master's thesis in Civil-Hydraulic Structures, Sistan& Balouchestan university, zahedan, 1390. (In Persian).
[15] A. Erfanain, A.A. Kamanbedast, Determine the appropriate location of aerator system on gotvandoliadam's spillway using Flow 3D, American-Eurasian Journal of Agricultural & Environmental Sciences 13(3) (2013) 378-383.
[16] k. Golparian, B. Amin nezhad, Numerical Investigation of the Impact of Overflow Aeration Dimensions on Cavitation Index in Free Dam Overflow and Comparison of Results with Laboratory Model in:  4th International Conference on Advanced Technology in Civil Engineering, Tehran, Tehran, 1396. (In Persian).
[17] s. Rasouli, j. Bazargan, Check the slope of the aeration ramp on the flow aeration in the chute, in:  4th International Conference on New Horizons in Civil Engineering,Architecture and Urbanism, New Horizons Science and Technology Association, Tehran, 1397. (In Persian)
[18] j. Mehrabady, Case study of variables affecting the probability of cavitation on chute, in:  3rd International Conference on Applied Research in Structural Engineering and Construction Management Sharif University of Technology, Tehran, 1398. (In Persian)
[19] P. Teng, J. Yang, M. Pfister, Studies of two-phase flow at a chute aerator with experiments and CFD modelling, in:  Modelling and Simulation in Engineering Hindawi Publishing Corporation, 2016, pp. 1-11.
[20] M. Marosi, R. Roshan, Analysis and Designing using Flow-3d, FadakIstasis, Tehran, 1393. (In Persian)
[21] I.R. Wood, Uniform region of self-aerated flow, Journal of Hydraulic Engineering 109(3) (1983) 447-461.
[22] K. Kramer, Development of Aerated Chute Flow, ETH Zurich, Doctoral Thesis ETH No. 15428, Technical University of Darmstadt (TUD), 2004.
[23] J.A. Kells, C.D. Smith, Reduction of cavitation on spillways by induced air entrainment, canadian journal of civil engineering 18(3) (1991) 358-377.
[24] H. Hasanabady, A. Khosrojerdi, Effect of aeration on free dam overflow using Flow-3d, in:  Eighth National Congress of Civil Engineering,, Babol, Iran, 1393.(In Persian)
Amirkabir Journal of Mechanical Engineering
Volume 53, Issue 5 (Special Issue)
August 2021
Pages 3135-3150

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