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Thermally driven exchange flow between open water and an aquatic canopy

Published online by Cambridge University Press:  27 July 2009

XUEYAN ZHANG  and
HEIDI M. NEPF
XUEYAN ZHANG*
Affiliation:
Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
HEIDI M. NEPF
Affiliation:
Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
*
†Email address for correspondence: [email protected]
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Abstract

Differential solar heating can result from shading by rooted emergent aquatic plants, producing a temperature difference between vegetated and unvegetated regions of a surface water body. This temperature difference will promote an exchange flow between the vegetation and open water. Drag associated with the submerged portion of the plants modifies this exchange, specifically, changing the dominant velocity scale. Scaling analysis predicts several distinct flow regimes, including inertia-dominated, drag-dominated and energy-limiting regimes. After a constant heat source is initiated, the flow is initially inertial, but quickly transitions to the drag-dominated regime. The energy-limiting regime is not likely to occur in the presence of rooted vegetation. Laboratory experiments describe the exchange flow and confirm the scaling analysis. Particle Imaging Velocimetry (PIV) was used to quantify the velocity field. Once the exchange flow enters the drag-dominated regime, the intrusion velocity uV is steady. The intrusion velocity decreases with increasing density of vegetation. The thickness of the intruding layer is set by the length scale of light penetration.

Type
Papers
Information
Journal of Fluid Mechanics , Volume 632 , 10 August 2009 , pp. 227 - 243
Copyright
Copyright © Cambridge University Press 2009

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References

REFERENCES

Adams, E. E. & Wells, S. A. 1984 Field measurements on side arms of Lake Anna, VA. J. Hydraul. Engng 110 (6), 773–793.CrossRefGoogle Scholar
Burke, R. W. & Stolzenbach, K. D. 1983 Free surface flow through salt marsh grass. MIT Sea Grant Coll. Program Rep. MITSG 83-16. Massachusetts Institute of Technology.Google Scholar
Chimney, M. J., Wenkert, L. & Pietro, K. C. 2006 Patterns of vertical stratification in a subtropical constructed wetland in south Florida (USA). Ecol. Engng 27, 322–330.CrossRefGoogle Scholar
Coates, M. & Ferris, J. 1994 The radiatively driven natural convection beneath a floating plant layer. Limnol. Oceanogr. 39 (5), 1186–1194.Google Scholar
Coates, M. J. & Patterson, J. C. 1993 Unsteady natural convection in a cavity with non-uniform absorption of radiation. J. Fluid Mech. 256, 133–161.CrossRefGoogle Scholar
Farrow, D. E. 2004 Periodically forced natural convection over slowly varying topography. J. Fluid Mech. 508, 1–21.CrossRefGoogle Scholar
Farrow, D. E. & Patterson, J. C. 1993 On the response of a reservoir sidearm to diurnal heating and cooling. J. Fluid Mech. 246, 143–161.CrossRefGoogle Scholar
Gharib, M. & Daribi, D. 2000 Digital particle image velocimetry. In Flow Visualization (ed. Smits, A. J. & Lim, T. T.), Chapter 6, pp. 123–147. Imperial College Press.CrossRefGoogle Scholar
Horsch, G. M. & Stefan, H. G. 1988 Convective circulation in littoral water due to surface cooling. Limnol. Oceanogr. 33 (5), 1068–1083.CrossRefGoogle Scholar
Jamali, M., Zhang, X. & Nepf, H. M. 2008 Exchange flow between a canopy and open water. J. Fluid Mech. 611, 237–254.CrossRefGoogle Scholar
James, W. F. & Barko, J. W. 1991 Estimation of phosphorus exchange between littoral and pelagic zones during nighttime convection circulation. Limnol. Oceanogr. 36 (1), 179–187.CrossRefGoogle Scholar
James, W. F., Barko, J. W. & Eakin, H. L. 1994 Convective water exchanges during differential cooling and heating: implications for dissolved constituent transport. Hydrobiologia 394, 167–176.CrossRefGoogle Scholar
Kadlec, R. C. 1990 Overland flow in wetlands: vegetation resistance. J. Hydraul. Engng 166 (5), 691–706.CrossRefGoogle Scholar
Koch, D. L. & Ladd, A. J. C. 1997 Moderate Reynolds number flows through periodic and random arrays of aligned cylinders. J. Fluid Mech. 349, 31–66.CrossRefGoogle Scholar
Lei, C. & Patterson, J. C. 2002 a Natural convection in a reservoir sidearm subject to solar radiation: experimental observations. Exp. Fluids 552, 207–220.Google Scholar
Lei, C. & Patterson, J. C. 2002 b Unsteady natural convection in a triangular enclosure induced by absorption of radiation. J. Fluid Mech. 460, 181–209.CrossRefGoogle Scholar
Lightbody, A., Avener, M. & Nepf, H. M. 2008 Observations of short-circuiting flow paths within a constructed treatment wetland in Augusta, Georgia, USA. Limnol. Oceanogr. 53 (3), 1040–1053.CrossRefGoogle Scholar
MacIntyre, S. & Melack, J. M. 1995 Vertical and horizontal transport in lakes. Linking moral, benthic, and pelagic habitats. J. N. Am. Benthol. Soc. 14 (4), 599–615.CrossRefGoogle Scholar
Monismith, S. G., Imberger, J. & Morison, M. L. 1990 Convective motions in the sidearm of a small reservoir. Limnol. Oceanogr. 35 (8), 1676–1702.CrossRefGoogle Scholar
Oldham, C. E. & Sturman, J. J. 2001 The effect of emergent vegetation on convective flushing in shallow wetlands: scaling and experiment. Limnol. Oceanogr. 46 (6), 1486–1493.CrossRefGoogle Scholar
Patterson, J. C. 1984 Unsteady natural convection in a cavity with non-uniform absorption of radiation. J. Fluid Mech. 140, 135–151.CrossRefGoogle Scholar
Pokorný, & Květ, 2004 Aquatic plants and lake ecosystems. In The Lakes Handbook (ed. O'Sullivan, P. E. & Reynolds, C. S.), vol. 1, Chapter 11, pp. 309–340. Blackwell Science.Google Scholar
Sturman, J. J. & Ivey, G. N. 1998 Unsteady convective exchange flows in cavities. J. Fluid Mech. 386, 127–153.CrossRefGoogle Scholar
Sturman, J. J., Oldham, C. E. & Ivey, G. N. 1999 Steady convective exchange flows down slopes. Aquat. Sci. 61, 260–278.CrossRefGoogle Scholar
Sveen, J. K. 2004 An introduction to MatPIV v. 1.6.1. Internet Resources.Google Scholar
Tanino, Y. & Nepf, H. M. 2008 Lateral dispersion in random cylinder arrays at high Reynolds number. J. Fluid Mech. 600, 339–371.CrossRefGoogle Scholar
Tanino, Y., Nepf, H. M. & Kulis, P. S. 2004 Gravity currents in aquatic canopies. Water Resour. Res. 41 (12), W12402. doi: 10.1029/2005WR004216.Google Scholar
Trevisan, O. V. & Bejan, A. 1986 Convection driven by the non uniform absorption of thermal radiation at the free-surface of a stagnant pool. Numerical Heat Transfer, 10 (5), 483–506.CrossRefGoogle Scholar
Ultsch, G. 1973 The effect of water hyacinth (Eichhornia crassipes) on the microenvironment of aquatic communities. Arch. Hydrobiologia 72, 460–473.Google Scholar
Wetzel, R. G. 2001 Light in inland water. In Limnology, 3rd ed. Academic Press.Google Scholar
Zhang, X. & Nepf, H. M. 2008 Density driven exchange flow between open water and an aquatic canopy. Water Resour. Res. 44 (8), W08417. doi: 10.1029/2007WR006676.CrossRefGoogle Scholar