Journal
ESTUARINE COASTAL AND SHELF SCIENCE
Volume 114, Issue -, Pages 23-30Publisher
ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD
DOI: 10.1016/j.ecss.2011.08.020
Keywords
oscillating grid turbulence; submerged aquatic vegetation; non-dimensional model; turbulent kinetic energy; power law; sheltering
Categories
Funding
- Ministerio de Ciencia e Innovacion of the Spanish Government [CGL 2010-17289]
- University of Girona [BR08/11]
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The aim of this study is to model, under controlled laboratory conditions, the effect of submerged aquatic vegetation (SAV) on turbulence generated in a water column by an oscillating grid turbulence (OGT). Velocity profiles have been measured by an acoustic Doppler velocimeter (MicroADV). Experimental conditions are analysed in two canopy models (rigid and semi-rigid), using nine plant-to-plant distances (ppd), three stem diameters (d), four types of natural SAV (Cladium mariscus, Potamogeton nodosus, Myriophyllum verticillatum and Ruppia maritima) and two oscillation grid frequencies (f). To quantify this response, we have developed a non-dimensional model, with a specific turbulent kinetic energy (TKE), f, stroke (s), d, ppd, distance from the virtual origin to the measurement (z(m)) and space between grid bars (M). The experimental data show that, at z(m)/z(c) < 1 the turbulent kinetic energy decays with z(m), according to the well-known power law, z(m)(-2), and does not depend on the vegetation characteristics. In contrast, at z(m)/z(c) > 1, TKE decreases faster with z(m) and scales to the model variables according to TKE0/(f(2).s(2)) proportional to (d/ppd)(-0.25).(z(m)/M)(-3). Therefore, at z(m)/z(c) > 1 the TKE is affected by the geometric characteristics of the plants (both diameter and plant-to-plant distance), an effect called sheltering. Results from semi-rigid canopies and natural SAV are found to scale with the nondimensional model proposed for rigid canopies. We also discuss the practical implications for field conditions (wind and natural SAV). (C) 2011 Elsevier Ltd. All rights reserved.
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