NAFEMS International Journal of CFD Case Studies

Volume 11, April 2016

ISSN 1462-236X

Analysis of High Velocity Free Surface Flow Interaction with a Bridge Pier in a Trapezoidal Channel using CFD

AA Abo¹, D Greaves², RJ Muhammad³, A Raby² and A Kyte^2
1Marine Institute and School of Marine Science & Eng., Plymouth Univ., UK, and formerly College of Eng. University of Salahaddin -Hawler, Iraq.
²Marine Institute and School of Marine Science & Eng., Plymouth Univ., UK.
³Dept. of Water Resources Eng., Univ. of Duhok, Duhok-Iraq.

https://doi.org/10.59972/8xzkaqhw

Keywords: High Velocity, Free Surface Flow, Single Bridge Pier, Turbulence and Non-dimensional

Abstract

This study uses the computational fluid dynamics (CFD) code ANSYS-CFX-12, to simulate 3D flow through a straight trapezoidal cross section channel containing a single bridge pier. The fluid flow condition is assumed to be steady state, isothermal and incompressible, with symmetry along the centerline of the channel, and the simulation uses the k - &epsilon turbulence model. The study investigates the impact of variations of aspect ratio (channel bed width/flow depth), bed and side slopes of the channel, discharge (represented by a Froude number), and the length and thickness of the bridge pier on the free surface flow profile, both along the centerline and the on the wall of the channel. The code is based on the finite volume method, and uses the volume of fluid (VOF) approach to predict the free surface flow profile.
Prediction of the free surface flow profile is essential for the design of high velocity channels. Prior prediction of flow profiles can inform and improve the design of expensive structures, such as high velocity channels and bridges, in particular the height of channel walls and bridge decks.
Firstly, the code was validated against the numerical and experimental work of Stockstill (1996) for a channel containing three piers, and found to agree well. Then, the method was applied to the design test case, and mesh convergence tests to establish the required mesh size were carried out.
The simulations were conducted in parallel over 32 cores on the Plymouth University High Performance Computer Cluster (HPCC).
Finally, a parametric study was carried out and analytical expressions derived for maximum flow depth at the centre-line and at the side wall of the channel. Useful non-dimensional curves and equations derived from regressions of the study data are provided, which can be used as a guideline for the design of high velocity channels containing a bridge pier. For data regressions the statistical package software Statistical Product and Service Solutions (SPSS) was used.

References

ANSYS, I. (2009) ANSYS-CFX, version 12.0, . (Version 14) [Computer Program]. Canonsburg, PA. : Available

Berger, R. & Stockstill, R. (1995) 'Finite-element model for high-velocity channels'. J. Hydr. Eng., 121 (10). pp 710-716.

Chiu, C. L. (1988) 'Entropy and 2-D velocity distribution in open channels'. J. Hydr. Eng., 114 (7). pp 738-756.

French, R. H. (1985) Open Channel Hydraulics. 2nd Printing 1987 Singapore: McGraw-Hill Book New Yourk.

Hirt, C. W. & Nichols, B. D. (1981) 'Volume of fluid (VOF) method for the dynamics of free boundaries'. Journal of computational physics, 39 (1). pp 201-225.

Hos, C. & Kullman, L. (2007) 'A numerical study on the free-surface channel flow over a bottom obstacle'. Journal of Hydraulic Research, 42 (3). pp 263–272.

Ippen, A. T. (1951) 'High-Velocity Flow in Open Channels: A Symposium: Mechanics of Supercritical Flow'. Transactions of the American Society of Civil Engineers, 116 (1). pp 268-295.

Ippen, A. T. & Dawson, J. H. (1951) 'High-Velocity Flow in Open Channels: A Symposium: Design of Channel Contractions'. Transactions of the American Society of Civil Engineers, 116 (1). pp 326-346.

Kallaka, T. & Wang, C. J. (2011) 'Efficient Numerical Model for Studying Bridge Pier Collapse in Floods'. World Acad Sci Eng Technol, 60 pp 1011-1016.

Knapp, R. T. (1951) 'High-Velocity Flow in Open Channels: A Symposium: Design of Channel Curves for Supercritical Flow'. Transactions of the American Society of Civil Engineers, 116 (1). pp 296-325.

Lai, Y. G. (2010) ' Two-Dimensional Depth Averaged Flow Modelling with an Unstructured Hybrid Mesh. '. J. Hydr. Eng ASCE. , 136 (1). pp 12-23.

Lai, Y. G. & Greimann, B. P. (2010) 'Predicting contraction scour with a two-dimensional depth-averaged model'. Journal of Hydraulic Research, 48 (3). pp 383-387.

Lai, Y. G., Weber, L. J. & Patel, V. C. (2003) 'Nonhydrostatic three-dimensional model for hydraulic flow simulation. I: Formulation and verification'. J. Hydr. Eng., 129 (3). pp 196-205.

Marriott, M. J. & Jayaratne, R. (2010) 'Hydraulic roughness–links between Manning’s coefficient, Nikuradse’s equivalent sand roughness and bed grain size', Nikuradse’s equivalent sand roughness and bed grain size’Proceedings of Advances in Computing and Technology,(AC&T) The School of Computing and Technology 5th Annual Conference, University of East London. University of East London, School of Computing, Information Technology and Engineering, pp. 27-32.

MMSWM (1976) ' Manual of the management of storm water in mancipal area for -Iraq '.[in first edition edn.] (Accessed:MMSWM)

Rouse, H., Bhoota, B. & Hsu, E.-Y. (1951) 'High-Velocity Flow in Open Channels: A Symposium: Design of Channel Expansion'. Transactions of the American Society of Civil Engineers, 116 (1). pp 347-363.

Stockstill, R. L. (1996) A Two-Dimensional Free-Surface Flow Model for Trapezoidal High-Velocity Channels. DTIC Document. Available.

Stockstill, R. L. B., R. C. and Nece, R. E. (1997) 'Two-dimensional flow model for trapezoidal high-velocity channels'. J. Hydr. Eng. ASCE, 123 (10). pp 844-852.

Cite this paper

AA Abo, D Greaves, RJ Muhammad, A Raby, A Kyte, Analysis of High Velocity Free Surface Flow Interaction with a Bridge Pier in a Trapezoidal Channel using CFD, NAFEMS International Journal of CFD Case Studies, Volume 11, 2016, Pages 5-29, https://doi.org/10.59972/8xzkaqhw