Numerical modelling of flow field in compound channels with non-prismatic floodplains

Document Type : Article


Department of Civil Engineering, Bu - Ali Sina University, Hamedan, Iran


In this paper an attempt has been made to study flow field in compound channels with non-prismatic floodplains. A three dimensional computational fluid dynamic (CFD) model is used to calculate the velocity distribution, secondary flow circulation and boundary shear stress in non-prismatic compound channels with two different convergence angles of 3.81o and 11.31o. The ANSYS-CFX software and k-e turbulence model is used to solve Reynolds Averaged Navier-Stokes (RANS) equations. The results of the numerical modeling were then compared to the experimental data on non-prismatic compound channels with the same convergence angles. The study shows that, more or less, the k-e turbulence model is capable of predicting the velocity and boundary shear stress distributions along the flume fairly well, especially for convergence angle of 3.81o. Also by increasing relative depth, discrepancy between numerical and experimental data decreases. The results of modeling show that the k-eturbulence model is able to predict secondary flow circulations in the main channel, created by the mass exchange between the floodplains and the main channel.


Main Subjects

1. Rezaei, B. \Overbank
ow in compound channels with
prismatic and non-prismatic
oodplains", PhD Thesis,
Birmingham University, UK (2006).
2. Tominaga, A. and Nezu, I. \Turbulent structure in
compound open-channel
ows", Journal of Hydraulic
Engineering, 117(1), pp. 21-41 (1991).
3. Bousmar, D. \Flow modeling in compound channels
-Momentum transfer between main channel and
prismatic or non-prismatic
oodplains", PhD Thesis,
Universite Catholique de Louvain, Belgium (2002).
4. Bousmar, D. and Zech, Y. \Momentum transfer for
ow computation in compound channel",
Journal of Hydraulic Engineering, 125(7), pp. 696-706
5. Bousmar, D., Wilkin, N., Jacquemart, J.H., and Zech,
Y. \Overbank
ow in symmetrically narrowing
Journal of Hydraulic Engineering, 130(4), pp.
305-312 (2004).
6. Proust, S., Riviere, N., Bousmar, D., Paquier, A.,
Zech, Y., and Morel, R. \Flow in compound channel
with abrupt
oodplain contraction", Journal of Hydraulic
Engineering, 132(9), pp. 958-970 (2006).
7. Rezaei, B. and Knight, D.W. \Overbank
ow in
compound channels with non-prismatic
Journal of Hydraulic Engineering, 137(8), pp. 815-824
8. Bousmar, D. and Zech, Y. \Discussion of twodimensional
solution for straight and meandering overbank

ows", D.A. Ervine, K. Babaeyan-Koopaei, and
Robert H.J. Sellin, Journal of Hydraulic Engineering,
126(9), pp. 653-669 (2000); Journal of Hydraulic
Engineering, 128(5), pp. 550-551 (2002).
9. Pezzinga, G. \Velocity distribution in compound channel

ows by numerical modeling", Journal of Hydraulic
Engineering, 120(10), pp. 1176-1197 (1994).
10. Kang, H. and Choi, S.U. \Turbulence modeling of
compound open-channel
ows with and without vegetation
on the
oodplain using the Reynolds stress
model", Advances in Water Resources, 29, pp. 1650-
1664 (2006).
11. Cokljat, D. \Turbulence models for non-circular ducts
and channels", PhD Thesis, City University London,
UK (1993).
12. Wright, N.G., Crosseley, A.J., Morvan, H.P., and
Stoesser, T. \Detailed validation of CFD for
ows in
straight channels", River Flow, Naples, Italy (2004).
13. Beaman, F. \Large eddy simulation of open channel

ows for conveyance estimation", PhD Thesis, Nottingham
University, UK (2010).
14. Bombardelli, F.A., Meireles, I., and Matos, J. \Laboratory
measurements and multi-block numerical simulations
of the mean
ow and turbulence in the nonaerated
ow region of steep stepped spillways",
Environmental Fluid Mechanics, 11(3), pp. 263-288
15. Bayon, A., Valero, D., Bartula, R.G., Moran, F.J.V.,
and Jimenez, P.A.L. \Performance assessment of
OpenFOAM and FLOW-3D in the numerical modeling
of a low Reynolds number hydraulic jump", Environmental
modelling & Software, 80, pp. 322-335 (2016).
16. Gholami, A., Akhtari, A.A., Minatour, Y., Bonakdary,
H., and Javadi, A.A. \Experimental and numerical
study on velocity eld and water surface pro le in
a strongly-curved 90 open channel bend", Journal
of Engineering Applications of Computation
uid Mechanics,
8(3), pp. 447-461 (2014).
17. Patel, V.C. \Calibration of the Preston tube and
limitations on its use in pressure gradients", Journal
of Fluid Mechanics, 23, pp. 85-208 (1965).
18. Davidson, P.A., Turbulence - An Introduction for
Scientists and Engineers, Oxford University Press, UK
19. Launder, B.E. and Spalding, D.B. \The numerical
computation of turbulent
ows", Computer Method
and Application and Engineering, 3(2), pp. 269-289
20. Versteeg, H.K. and Malalasekera, W. \An introduction
to computational
uid dynamics", The Finite Volume
Method, 2nd Edn., Pearson Education Limited, Essex,
England (2007).
21. Bonakdari, H., Baghalian, S., Nazari, F., and Fazli,
M. \Numerical analysis and prediction of the velocity
eld in curved channel using arti cial neural network
and genetic algorithm", Journal of Engineering Applications
of Computation
uid Mechanics, 5(3), pp.
384-396 (2011).
2424 B. Rezaei and H. Amiri/Scientia Iranica, Transactions A: Civil Engineering 25 (2018) 2413{2424
22. Morvan, N., Pender, G., Wright, N.G., and Ervine,
D.A. \Three-Dimensional hydrodynamics of meandering
compound channels", Journal of Hydraulic Engineering,
128(7), pp. 674-682 (2002).
23. Hirt, C.W. and Nichols, B.D. \Volume of
uid (VOF)
method for the dynamics of free boundaries", Journal
of Computational Physics, 39(1), pp. 201-225 (1981).
24. Celik, I.B., Ghia, U. and Roache, P.J. \Procedure
for estimation and reporting of uncertainty due to
discretization in CFD applications", ASME Journal of
Fluids Engineering, 130(7), pp. 1-4 (2008).