Advertisement

Acta Geophysica

, Volume 67, Issue 3, pp 961–970 | Cite as

Turbulent mixing and dispersion mechanisms over flexible and dense vegetation

  • Donatella TerminiEmail author
Research Article - Special Issue

Abstract

The present study investigates flow turbulence and dispersion processes in the presence of flexible and dense vegetation on the bed. The turbulent dispersion coefficients and the terms of the turbulent kinetic energy equation are determined by using data collected in a straight laboratory channel with living vegetation on the bed. Results show that the turbulent integral lengths assume an order of magnitude comparable to the stems’ characteristic dimension independently by the direction and the turbulence assumes an isotropic behavior. The coefficients of dispersion have a trend similar to that of the turbulent lengths and assume low values in the longitudinal, transversal and vertical directions. Results also show that, in the mixing layer, the shear and wake turbulence production terms balance the dissipation; the turbulent diffusion term also assumes low values and its sign varies along the vertical indicating a transport of turbulent energy both from the vegetation to the free surface and from the free surface to vegetation.

Keywords

Vegetated channels Flexible vegetation Turbulence Dispersion 

References

  1. Ackerman JD, Okumbo A (1993) Reduced mixing in a marine macrophyte canopy. Funct Ecol 7:305–309Google Scholar
  2. Antonia RA, Kim J, Browne LWB (1991) Some characteristics of small-scale turbulence in a turbulent duct flow. J Fluid Mech 233:368–388Google Scholar
  3. Brunet Y, Finnigan J, Raupach MR (1994) A wind tunnel study of air flow in waving wheat: single-point velocity statistics. Bound-Layer Meteorol 70:95–132Google Scholar
  4. Carollo FG, Ferro V, Termini D (2002) Flow velocity measurement in vegetated channels. J Hydraul Eng ASCE 128(7):664–673Google Scholar
  5. Carollo FG, Ferro V, Termini D (2005) Flow resistance law in channels with flexible submerged vegetation. J Hydraul Eng 131:554–564Google Scholar
  6. Carollo FG, Ferro V, Termini D (2006) Experimental investigation of flow characteristics in vegetated channels. International Congress Riverflow 2006—Lisbon (Portugal) 6–8 SeptGoogle Scholar
  7. Carollo FG, Ferro V, Termini D (2007) Analysing longitudinal turbulence intensity in vegetated channels. J Agric Eng 4:25–35Google Scholar
  8. Carollo FG, Ferro V, Termini D (2008) Determinazione del profilo di velocità e di intensità della turbolenza in canali vegetati, 31° Convegno Nazionale di Idraulica e Costruzioni Idrauliche, 9–12 Sept Perugia, Italy (in Italian) Google Scholar
  9. Carpenter SR, Lodge DM (1986) Effects of submersed macrophytes on ecosystem processes. Aquat Bot 26:341–370Google Scholar
  10. Chandler M, Colarusso P, Buchsbaum R (1996) A study of eelgrass beds in Boston Harbor and Northern Massachusetts bays. Proj. Rep. Off. Res. Dev. US EPA, Narragansett, RIGoogle Scholar
  11. Coceal O, Dobre TG, Thomas TG, Belcher SE (2007) Structure of turbulent flow over regular arrays of cubical roughness. J Fluid Mech 589:375–409Google Scholar
  12. Corenblit D, Tabacchi E, Steiger J, Grunell AM (2007) Reciprocal interactions and adjustments between fluvial landforms and vegetation dynamics in river corridors: a review of complementary approaches. Earth Sci Rev 84(1–2):56–86Google Scholar
  13. Cornacchia L, Licci S, Nepf H, Folkard A, van der Wal D, van de Koppel J, Puijalon S, Bouma TJ (2018) Turbulence-mediated facilitation of resource uptake in patchy stream macrophytes. Limnol Oceanog.  https://doi.org/10.1002/lno.11070 Google Scholar
  14. De Serio F, Ben Meftah M, Mossa M, Termini D (2018) Experimental investigation on dispersion mechanisms in rigid and flexible vegetated beds”. Adv Water Resour 120:98–113Google Scholar
  15. Defina A, Bixio AC (2005) Mean flow and turbulence in vegetated open channel flow. Water Resour Res 41:W07006.  https://doi.org/10.1029/2004WR003475 Google Scholar
  16. Ellenberg HH (2009) Vegetation ecology on Central Europe. Cambridge University Press, CambridgeGoogle Scholar
  17. Finnigan JJ, Shaw RH (2008) Double-averaging methodology and its application to turbulent flow in and above vegetation canopies. Acta Geophys 56(3):534–561Google Scholar
  18. Folkard AM (2011) Vegetated flows in their environmental context: a review. Eng Comput Mech ICE Proc 164(EM1):3–24Google Scholar
  19. Ghisalberti M, Nepf H (2006) The structure of the shear layer in flows over rigid and flexible canopies. Environ Fluid Mech 6:277–301Google Scholar
  20. Khaleghi E, Ramin AA (2005) Study of the effects of salinity on growth and development of lawns (Lolium perenne L., Festuca arundinacea and Cynodon dactylon). JWSS 9(3):57–68Google Scholar
  21. Kubrak E, Kubrak J, Kiczko A (2015) Experimental Investigation of kinetic energy and momentum coefficients in regular channels with stiff and flexible elements simulating submerged vegetation. Acta Geophys 63(5):1405–1422Google Scholar
  22. Lawn CJ (1971) The determination of the rate of dissipation in turbulent pipe flow. J Fluid Mech 48:477–505Google Scholar
  23. Leuven RSEW, Ragas AMJ, Smits AJM, van der Velde G (2006) Living rivers: trends and challenges in science and management. Springer, AmsterdamGoogle Scholar
  24. Łoboda AM, Bialik RJ, Karpiński M, Przyborowski Ł (2019) Two simultaneously occurring Potamogeton species: similarities and differences in seasonal changes of biomechanical properties. Pol J Environ Stud 28(1):1–16Google Scholar
  25. Lumley JL (1965) Interpretation of time spectra measured in high-intensity shear flows. Phys Fluids 6:1056–1062Google Scholar
  26. Nepf H (1999) Drag, turbulence and diffusivity in flow through emergent vegetation. Water Resour Res 35(2):479–489Google Scholar
  27. Nepf HM (2012) Hydrodynamics of vegetated channels. J Hydraul Res 50(3):262–279Google Scholar
  28. Nepf H, Ghisalberti M (2008) Flow and transport in channels with submerged vegetation. Acta Geophys 56(3):753–777Google Scholar
  29. Nepf H, Vivoni E (2000) Flow structure in depth-limited, vegetated flow. J Geophys Res 105(C12):28547–28557Google Scholar
  30. Nepf H, Koch EW (1999) Vertical secondary flows in submersed plant-like arrays. Limnology and Oceanography 44(4):1072–1080Google Scholar
  31. Nepf H, Mugnier C, Zavistoski R (1997) The effects of vegetation on longitudinal dispersion. Estuar Coast Shelf Sci 44:675–684Google Scholar
  32. Nezu I, Nakagawa H (1993) Turbulence on open channel flows. A.A. Balkema Publishers, RotterdamGoogle Scholar
  33. Nezu I, Sanjou M (2008) Turbulence structure and coherent motion in vegetated canopy open-channel flows. J Hydro-environ Res 2:62–90Google Scholar
  34. Nikora V, Goring DG, McEwan I, Griffiths G (2001) Spatially-averaged open-channel flow over a rough bed. J Hydraul Eng ASCE 127(2):123–133Google Scholar
  35. Nikora V, Lamed S, Nikora N, Debnath K, Cooper G, Reid M (2008) Hydraulic resistance due to aquatic vegetation in small streams: field study. J Hydraul Eng 134(9):1326–1332Google Scholar
  36. Okamoto T, Nezu I (2009) Turbulence structure and “Monami” phenomena in flexible vegetated open-channel flows. J Hydraul Res 47:798–810Google Scholar
  37. Oldham CE, Sturman JJ (2001) The effect of emergent vegetation on convective flushing in shallow wetlands: scaling and experiments. Limnol Oceanogr 46(6):1486–1493Google Scholar
  38. Poggi D, Porporato A, Ridolfi L, Albertson JD, Katul GG (2004) The effect of vegetation density on canopy sub-layer turbulence. Bound-Layer Meteorol 111:565–587Google Scholar
  39. Poggi D, Krug C, Katul GG (2009) Hydraulic resistance of submerged rigid vegetation derived from first-order closure models. Water Resour Res 45:W10442Google Scholar
  40. Pope SB (2000) Turbulent flows. Cambridge University Press, CambridgeGoogle Scholar
  41. Raupach M, Shaw R (1982) Averaging procedures for flow within vegetation canopies. Bound-Layer Meteorol 22:79–90Google Scholar
  42. Raupach MR, Coppin PA, Legg BJ (1986) Experiments on scalar dispersion in a model plant canopy, part I: the turbulence structure. Bound-Layer Meteorol 35:21–52Google Scholar
  43. Ricardo AM, Koll K, Franca MJ, Schleiss A, Ferreira RML (2014) The terms of turbulent kinetic energy budget within random arrays of emergent cylinders. Water Resour Res 50:4131–4148Google Scholar
  44. Righetti M (2008) Flow analysis in a channel with flexible vegetation using double-averaging method. Acta Geophys 56:801Google Scholar
  45. Rutherford JC (1994) River mixing. Cambridge University Press, CambridgeGoogle Scholar
  46. Schnauder I, Sukhodolov AN (2012) Flow in a tightly curving meander bend: effects of seasonal changes in aquatic macrophyte cover. Earth Surf Proc Land 37(11):1142–1157Google Scholar
  47. Schultz RC, Colletti JP, Isenhart TM, Simpkins WW, Mize CW, Thompson ML (1995) Design and placement of a multi-species riparian buffer system. Agrofor Syst 29:201–226Google Scholar
  48. Shucksmith JD, Boxall JB, Guymer I (2011) Determining longitudinal dispersion coefficients for submerged vegetated flow. Water Resour Res 47(W10516):1–13Google Scholar
  49. Sivpure V, Devi TB, Kumar B (2015) Analysing turbulent characteristics of flow over submerged flexible vegetated channel. ISH J Hydraul Eng 21(3):265–275Google Scholar
  50. Sivpure V, Bebi TB, Kumar B (2016) Turbulent characteristics of densely flexible submerged vegetated channel. ISH J Hydraul Eng 22(2):220–226Google Scholar
  51. Stoesser T, Kim S, Diplas P (2010) Turbulent flow through idealized emergent vegetation. J Hydraul Eng 136(12):1003–1017Google Scholar
  52. Tanino Y, Nepf H (2008) Lateral dispersion in random cylinder arrays at high Reynolds number. J Fluid Mech 600:339–371Google Scholar
  53. Termini D (2013) Effect of vegetation on fluvial erosion processes: experimental analysis in a laboratory flume. Procedia Environ Sci 19:904–911Google Scholar
  54. Termini D (2015) Flexible vegetation behavior and effects on flow conveyance: experimental observations. Int J River Basin Manage 13(4):401–411Google Scholar
  55. Termini D (2016) Experimental analysis of the effect of vegetation on flow and bed shear stress distribution in high-curvature bends. Geomorphology 274:1–10Google Scholar
  56. Termini D, Di Leonardo A (2018) Turbulence structure and implications in exchange processes in high-amplitude vegetated meanders: experimental investigation. Adv Water Resour 120:114–127 (in press) Google Scholar

Copyright information

© Institute of Geophysics, Polish Academy of Sciences & Polish Academy of Sciences 2019

Authors and Affiliations

  1. 1.Department of Engineering, Polytechnic SchoolUniversity of PalermoPalermoItaly

Personalised recommendations