Experimental and Numerical Investigation of Scouring Process around the Piers with Lateral Boundaries Fitted by Velocity Profile under Steady State Flow condition

Document Type : Research Article

Authors

1 MSc. in Civil Engineering, Marine Structures, Sahand University of Technology, Tabriz, Iran

2 Professor, Civil Engineering Faculty, Sahand University of Technology, Tabriz, Iran

Abstract

The piers’ shape may be considered as one of the key factors in controlling the scour process around it, as this mainly changes the stream flow pattern around the structure. Furthermore, piers with variable section in depth may also be of interest in reducing the scour around them. The aim of this study was to evaluate the effectiveness of the piers with lateral boundaries fitted by velocity profile due to steady flow, in reducing local scour, when compared to the circular and conical shaped piers. The section of the piers was circular and the widths or diameters of these piers reduce from bed to water surface with a slope fitted by velocity profile. Due to increasing flow discharge close to the water surface, the flow which has maximum velocity in this region will then pass around the piers easier than the cylindrical pier and its velocity is reduced. Therefore, in using these piers, the dynamic pressure in upper regions decreases relative to that of the cylindrical pier and there will be a weaker down flow in front of pier which will consequently cause decreasing of the scour depth. The models tested in this study were three models with logarithmic profiles fitted by (d50=0.78, 1.1, 1.3 mm) and three models with conical profiles by ( degrees, in which φ is the angle of lateral slope). Then, the relative scour depth for these models compared with the cylindrical reference model and the maximum scour depth decreased with the rate of 55.9%, 65.4%, 73.2%, 38.5%, 47.2% and 52.7%, respectively. These tests have been performed in a wide flume at hydraulic research laboratory and under clear water conditions over12 hours using relatively uniform sediments particles. For the numerical models, the maximum scour depth around the piers was simulated using Flow-3D model. It was found that the numerical model results were in reasonably good agreement with the experimental data.  

Keywords

References

پور احمدی ،م. (1389). "بررسی تجربی و عددی پدیده آبشستگی اطراف پایه مخروطی و هرمی." پایان نامه کارشناسی ارشد مهندسی سازه‌های دریایی، دانشگاه صنعتی سهند تبریز، تبریز، ایران.
توحیدی، ح. (1392). "بررسی عددی و تجربی فرایند آبشستگی اطراف پایه‌هایی با مرزهای جانبی متناسب با پروفیل سرعت تحت جریان دائمی"، پایان نامه کارشناسی ارشد مهندسی سازه‌های دریایی، دانشگاه صنعتی سهند تبریز، تبریز، ایران.
Breusers, H. and Raudkivi, A. (1991). "Scouring, hydraulic structures design manual", Vol. 2, Balkema, Rotterdam.
Flow Science, Inc. (2010). Flow-3D User’s Manual.
Fredsoe, J. and Sumer, B. M. (1997). "Scour at the round head of a rubble-mound breakwater", Journal of Coastal Engineering, Vol. 29, pp. 231-262.
Garde, R.J. and Ranga Raju, K.G. (1985). "Mechanism of sediment transportation and alluvial stream problems". Published by New Age International Limited, New Delhi.
Hakimzadeh, H., Mehrzad, R. and Azari, N. (2012). 'Experimental investigation of the effects of slotted conical shaped piers on scour process due to steady flow'. 6th Conference on Scour and Erosion, Paris, France.
Johnson, P. (1991) "Advancing bridge-pier scour engineering". Journal of Professional Issues in Engineering Education and Practice, Vol. 117.
Melville, B. and Chiew, Y. (1999). "Time scale for local scour at bridge piers". Journal of Hydraulic Engineering, ASCE, 125(1): pp. 59-65.
Melville, B. and Raudkivi, A. (1996). "Effects of foundation geometry on bridge pier scour". Journal of Hydraulic Engineering, Vol. 122, No. 4, pp. 203-9.
Raudkivi, A. and Ettema, R. (1983). "Clear-Water scour at cylindrical piers". Journal of Hydraulic Engineering, Vol. 109, No. 3, pp. 338-50.
Sanoussi, A. and Habib, A. (2008). "Local scour at rounded and sloped face piers with skew angles", The International Conference on Construction and
Building Technoloy, Kuala Lumpur, Malaysia, D(41), 439-461.
Shen, H.W. (1971). "River mechanics", Vol. 1 and Vol. 2, water resources publication. Department of Civil Engineering. Colorado State University.
Shen, H. and Schneider, V. (1969). "Local scour around bridge piers", Journal of the Hydraulics Division, Proceedings of the American Society of Civil Engineering, 95(6): pp. 1919-1941.
Sumer, B.M., Fredsoe, J., Christiansen, N., and Hensen, SB. (1994). "Bed shear stress and scour around coastal structures", Proc., 24th International Coastal Engineering Conference, e. Robert M. Ragan, ed., Kobe, Japan, ASCE, 1595–1609.
Sumer, B.M. and Fredsoe, J. (2002). The mechanics of the scour in the marine environment, Advanced Series on Ocean Engineering, Vol. 17, Word Scientific.
Tseng, M., Yen, C. and Song, C. (2000). "Computation of three-dimensional flow around square and circular piers", International Journal for Numerical Methods in Fluids, Vol. 34, No. 3, pp. 207-27.
Zhao, M. (2010). "Experimental and numerical investigation of local scour around a submerged vertical circular cylinder in steady currents", Journal of Coastal Engineering 57.
Journal of Hydraulics
Volume 9, Issue 4 - Serial Number 94
February 2015
Pages 39-53

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History

  • Receive Date: 07 July 2014
  • Revise Date: 16 February 2015
  • Accept Date: 27 May 2015

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