Advertisement

Environmental Fluid Mechanics

, Volume 16, Issue 6, pp 1173–1193 | Cite as

Combined effects of bed friction and emergent cylinder drag in open channel flow

  • Victor DupuisEmail author
  • Sébastien Proust
  • Céline Berni
  • André Paquier
Original Article

Abstract

Open channel flows subjected to a longitudinal transition in roughness, from bed friction to emergent cylinder drag and vice versa, are investigated experimentally in an 18-m-long laboratory flume. These are compared to uniform flows subject to (1) bed roughness only and (2) an array of emergent vertical cylinders installed on bed roughness. The near-bed region is investigated in detail for uniform flows through the cylinder array. The water column can be divided into two parts: a region of constant velocity and a boundary layer near the channel bed. In the latter region, a local increase in velocity, or velocity bulge, is observed in line of a cylinder row. The velocity bulge may be related to the disorganization of the von Kármán vortex street by the bed-induced turbulence, resulting in reduced momentum loss in the cylinder wake. The boundary layer height is found to be independent of water depth and bed roughness (smooth or rough bottom). Strong oscillations of the free surface (seiching) are observed. Oscillation amplitude is dependent on the longitudinal position within the cylinder array and is found to decrease with decreasing array length. When water depth/boundary layer height ratio is close to unity, the disorganization of the von Kármán vortex street throughout the water column prevents seiching from occurring. In the case of roughness transition flows, the water depth is found to vary only upstream of the change in roughness. Vertical profiles of velocity and turbulence are self-similar upstream of the transition and collapse with the uniform flow profiles. Downstream of the roughness change, velocity and turbulence vary over a distance of 35–50 times the water depth. Roughness transition flows show that seiching is lowered by flow non-uniformity. A 1D momentum equation integrating bed friction and drag force exerted by the cylinder array predicts accurately the water surface profile (0.9 % mean relative error). The computed profiles show that upstream of the transition, flow depth varies over a distance of about 2600 times the uniform water depth of the upstream roughness. The 1D equation is solved analytically for zero bed friction.

Keywords

Laboratory study Roughness transition Rigid vegetation Free surface oscillation Seiching 

Notes

Acknowledgments

The authors wish to thank Fabien Thollet for his technical support and Sheng Chen for his relevant suggestions. The Ph.D. grant of V. Dupuis was funded by Irstea and by the French National Research Agency (Flowres project, Grant No. ANR-14-CE03-0010, http://flowres.irstea.fr/).

References

  1. 1.
    Antonia R, Luxton R (1971) The response of a turbulent boundary layer to a step change in surface roughness Part 1. Smooth to rough. J Fluid Mech 48(04):721–761CrossRefGoogle Scholar
  2. 2.
    Carravetta A, Della Morte R (2004) Response of velocity to a sudden change of bed roughness in sub critical open channel flow. In: River Flow 2004: Proceedings of the Second International Conference on Fluvial Hydraulics, 23–25 June 2004, Napoli, Italy, Two Volme Set. CRC Press, p 389Google Scholar
  3. 3.
    Chanson H, Trevethan M, Koch C (2007) Discussion of “Turbulence measurements with acoustic Doppler velocimeters” by C. M. García, M. I. Cantero, Y. Niño, and M. H. García. J Hydraul Eng 133(11):1283–1286CrossRefGoogle Scholar
  4. 4.
    Chen X, Chiew YM (2003) Response of velocity and turbulence to sudden change of bed roughness in open-channel flow. J Hydraul Eng 129(1):35–43CrossRefGoogle Scholar
  5. 5.
    Chen X, Chiew YM (2004) Response of velocity and turbulence to sudden change of bed roughness in open-channel flow. J Hydraul Eng 130(6):589–590CrossRefGoogle Scholar
  6. 6.
    Cheng H, Castro IP (2002) Near-wall flow development after a step change in surface roughness. Bound-Layer Meteorol 105(3):411–432CrossRefGoogle Scholar
  7. 7.
    Defina A, Pradella I (2014) Vortex-induced cross-flow seiching in cylinder arrays. Adv Water Resour 71:140–148CrossRefGoogle Scholar
  8. 8.
    Dupuis V, Proust S, Berni C, Paquier A, Thollet F (2015) Open-channel flow over longitudinal roughness transition from highly-submerged to emergent vegetation. 36th IAHR World Congress, The HagueGoogle Scholar
  9. 9.
    Goring DG, Nikora VI (2002) Despiking acoustic Doppler velocimeter data. J Hydraul Eng 128(1):117–126CrossRefGoogle Scholar
  10. 10.
    Graf WH, Altinakar MS (1998) Fluvial hydraulics. Wiley, ChichesterGoogle Scholar
  11. 11.
    Jafari A, Ghomeshi M, Bina M, Kashefipour SM (2010) Experimental study on ten modes of transverse waves due to vertical cylinders in open channels. J Food Agric Environ 8(2):949–955Google Scholar
  12. 12.
    Kironoto B, Graf WH (1994) Turbulence characteristics in rough uniform open-channel flow. Proceedings of the ICE-Water Maritime and Energy 106(4):333–344CrossRefGoogle Scholar
  13. 13.
    Kothyari UC, Hayashi K, Hashimoto H (2009) Drag coefficient of unsubmerged rigid vegetation stems in open channel flows. J Hydraul Res 47(6):691–699CrossRefGoogle Scholar
  14. 14.
    Liu D, Diplas P, Fairbanks J, Hodges C (2008) An experimental study of flow through rigid vegetation. J Geophys Res: Earth Surf (2003–2012) 113(F4)Google Scholar
  15. 15.
    Martino R, Paterson A, Piva M (2012) Double-average mean flow and local turbulence intensity profiles from PIV measurements for an open channel flow with rigid vegetation. Environ Fluid Mech 12(1):45–62CrossRefGoogle Scholar
  16. 16.
    Nepf H (1999) Drag, turbulence, and diffusion in flow through emergent vegetation. Water Resour Res 35(2):479–489CrossRefGoogle Scholar
  17. 17.
    Nezu I, Rodi W (1986) Open-channel flow measurements with a laser Doppler anemometer. J Hydraul Eng 112(5):335–355CrossRefGoogle Scholar
  18. 18.
    Pendergrass W, Arya S (1984) Dispersion in neutral boundary layer over a step change in surface roughness—I. Mean flow and turbulence structure. Atmos Environ (1967) 18(7): 1267–1279Google Scholar
  19. 19.
    Poggi D, Porporato A, Ridolfi L, Albertson J, Katul G (2004) The effect of vegetation density on canopy sub-layer turbulence. Bound-Layer Meteorol 111(3):565–587CrossRefGoogle Scholar
  20. 20.
    Rabinovich AB (2009) Seiches and harbor oscillations. Handbook of coastal and ocean engineering, pp 193–236Google Scholar
  21. 21.
    Raupach M, Antonia R, Rajagopalan S (1991) Rough-wall turbulent boundary layers. Appl Mech Rev 44(1):1–25CrossRefGoogle Scholar
  22. 22.
    Robert A, Roy AG, de Serres B (1992) Changes in velocity profiles at roughness transitions in coarse grained channels. Sedimentology 39(5):725–735CrossRefGoogle Scholar
  23. 23.
    Rominger JT, Nepf HM (2011) Flow adjustment and interior flow associated with a rectangular porous obstruction. J Fluid Mech 680:636–659CrossRefGoogle Scholar
  24. 24.
    Sarkar A (2012) Vortex-excited transverse surface waves in an array of randomly placed circular cylinders. J Hydraul Eng 138(7):610–618CrossRefGoogle Scholar
  25. 25.
    Siuru W, Logan E (1977) Response of a turbulent pipe flow to a change in roughness. J Fluids Eng 99(3):548–553CrossRefGoogle Scholar
  26. 26.
    Stoesser T, Kim S, Diplas P (2010) Turbulent flow through idealized emergent vegetation. J Hydraul Eng 136:1003–1017Google Scholar
  27. 27.
    Terrier B (2010) Flow characteristics in straight compound channels with vegetation along the main channel. Ph.D. thesis, Loughborough UniversityGoogle Scholar
  28. 28.
    Yen BC (2002) Open channel flow resistance. J Hydraul Eng 128(1):20–39CrossRefGoogle Scholar
  29. 29.
    Zhao K, Cheng NS, Huang Z (2014) Experimental study of free-surface fluctuations in open-channel flow in the presence of periodic cylinder arrays. J Hydraul Res 52(4):465–475CrossRefGoogle Scholar
  30. 30.
    Zima L, Ackermann NL (2002) Wave generation in open channels by vortex shedding from channel obstructions. J Hydraul Eng 128(6):596–603CrossRefGoogle Scholar
  31. 31.
    Zong L, Nepf H (2010) Flow and deposition in and around a finite patch of vegetation. Geomorphology 116(3):363–372CrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media Dordrecht 2016

Authors and Affiliations

  • Victor Dupuis
    • 1
    Email author
  • Sébastien Proust
    • 1
  • Céline Berni
    • 1
  • André Paquier
    • 1
  1. 1.Irstea, UR HHLY Hydrologie-Hydraulique, Centre de Lyon-VilleurbanneVilleurbanne CedexFrance

Personalised recommendations