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.
Similar content being viewed by others
References
Ackerman JD, Okumbo A (1993) Reduced mixing in a marine macrophyte canopy. Funct Ecol 7:305–309
Antonia RA, Kim J, Browne LWB (1991) Some characteristics of small-scale turbulence in a turbulent duct flow. J Fluid Mech 233:368–388
Brunet Y, Finnigan J, Raupach MR (1994) A wind tunnel study of air flow in waving wheat: single-point velocity statistics. Bound-Layer Meteorol 70:95–132
Carollo FG, Ferro V, Termini D (2002) Flow velocity measurement in vegetated channels. J Hydraul Eng ASCE 128(7):664–673
Carollo FG, Ferro V, Termini D (2005) Flow resistance law in channels with flexible submerged vegetation. J Hydraul Eng 131:554–564
Carollo FG, Ferro V, Termini D (2006) Experimental investigation of flow characteristics in vegetated channels. International Congress Riverflow 2006—Lisbon (Portugal) 6–8 Sept
Carollo FG, Ferro V, Termini D (2007) Analysing longitudinal turbulence intensity in vegetated channels. J Agric Eng 4:25–35
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)
Carpenter SR, Lodge DM (1986) Effects of submersed macrophytes on ecosystem processes. Aquat Bot 26:341–370
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, RI
Coceal O, Dobre TG, Thomas TG, Belcher SE (2007) Structure of turbulent flow over regular arrays of cubical roughness. J Fluid Mech 589:375–409
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):56–86
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
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 120:98–113
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
Ellenberg HH (2009) Vegetation ecology on Central Europe. Cambridge University Press, Cambridge
Finnigan JJ, Shaw RH (2008) Double-averaging methodology and its application to turbulent flow in and above vegetation canopies. Acta Geophys 56(3):534–561
Folkard AM (2011) Vegetated flows in their environmental context: a review. Eng Comput Mech ICE Proc 164(EM1):3–24
Ghisalberti M, Nepf H (2006) The structure of the shear layer in flows over rigid and flexible canopies. Environ Fluid Mech 6:277–301
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):57–68
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):1405–1422
Lawn CJ (1971) The determination of the rate of dissipation in turbulent pipe flow. J Fluid Mech 48:477–505
Leuven RSEW, Ragas AMJ, Smits AJM, van der Velde G (2006) Living rivers: trends and challenges in science and management. Springer, Amsterdam
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):1–16
Lumley JL (1965) Interpretation of time spectra measured in high-intensity shear flows. Phys Fluids 6:1056–1062
Nepf H (1999) Drag, turbulence and diffusivity in flow through emergent vegetation. Water Resour Res 35(2):479–489
Nepf HM (2012) Hydrodynamics of vegetated channels. J Hydraul Res 50(3):262–279
Nepf H, Ghisalberti M (2008) Flow and transport in channels with submerged vegetation. Acta Geophys 56(3):753–777
Nepf H, Vivoni E (2000) Flow structure in depth-limited, vegetated flow. J Geophys Res 105(C12):28547–28557
Nepf H, Koch EW (1999) Vertical secondary flows in submersed plant-like arrays. Limnology and Oceanography 44(4):1072–1080
Nepf H, Mugnier C, Zavistoski R (1997) The effects of vegetation on longitudinal dispersion. Estuar Coast Shelf Sci 44:675–684
Nezu I, Nakagawa H (1993) Turbulence on open channel flows. A.A. Balkema Publishers, Rotterdam
Nezu I, Sanjou M (2008) Turbulence structure and coherent motion in vegetated canopy open-channel flows. J Hydro-environ Res 2:62–90
Nikora V, Goring DG, McEwan I, Griffiths G (2001) Spatially-averaged open-channel flow over a rough bed. J Hydraul Eng ASCE 127(2):123–133
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):1326–1332
Okamoto T, Nezu I (2009) Turbulence structure and “Monami” phenomena in flexible vegetated open-channel flows. J Hydraul Res 47:798–810
Oldham CE, Sturman JJ (2001) The effect of emergent vegetation on convective flushing in shallow wetlands: scaling and experiments. Limnol Oceanogr 46(6):1486–1493
Poggi D, Porporato A, Ridolfi L, Albertson JD, Katul GG (2004) The effect of vegetation density on canopy sub-layer turbulence. Bound-Layer Meteorol 111:565–587
Poggi D, Krug C, Katul GG (2009) Hydraulic resistance of submerged rigid vegetation derived from first-order closure models. Water Resour Res 45:W10442
Pope SB (2000) Turbulent flows. Cambridge University Press, Cambridge
Raupach M, Shaw R (1982) Averaging procedures for flow within vegetation canopies. Bound-Layer Meteorol 22:79–90
Raupach MR, Coppin PA, Legg BJ (1986) Experiments on scalar dispersion in a model plant canopy, part I: the turbulence structure. Bound-Layer Meteorol 35:21–52
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 50:4131–4148
Righetti M (2008) Flow analysis in a channel with flexible vegetation using double-averaging method. Acta Geophys 56:801
Rutherford JC (1994) River mixing. Cambridge University Press, Cambridge
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):1142–1157
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 29:201–226
Shucksmith JD, Boxall JB, Guymer I (2011) Determining longitudinal dispersion coefficients for submerged vegetated flow. Water Resour Res 47(W10516):1–13
Sivpure V, Devi TB, Kumar B (2015) Analysing turbulent characteristics of flow over submerged flexible vegetated channel. ISH J Hydraul Eng 21(3):265–275
Sivpure V, Bebi TB, Kumar B (2016) Turbulent characteristics of densely flexible submerged vegetated channel. ISH J Hydraul Eng 22(2):220–226
Stoesser T, Kim S, Diplas P (2010) Turbulent flow through idealized emergent vegetation. J Hydraul Eng 136(12):1003–1017
Tanino Y, Nepf H (2008) Lateral dispersion in random cylinder arrays at high Reynolds number. J Fluid Mech 600:339–371
Termini D (2013) Effect of vegetation on fluvial erosion processes: experimental analysis in a laboratory flume. Procedia Environ Sci 19:904–911
Termini D (2015) Flexible vegetation behavior and effects on flow conveyance: experimental observations. Int J River Basin Manage 13(4):401–411
Termini D (2016) Experimental analysis of the effect of vegetation on flow and bed shear stress distribution in high-curvature bends. Geomorphology 274:1–10
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)
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Termini, D. Turbulent mixing and dispersion mechanisms over flexible and dense vegetation. Acta Geophys. 67, 961–970 (2019). https://doi.org/10.1007/s11600-019-00272-8
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s11600-019-00272-8