The debate about drag and reconfiguration of freshwater macrophytes: comparing results obtained by three recently discussed approaches

Statzner, Bernhard; Lamouroux, Nicolas; Nikora, Vladimir; Sagnes, Pierre

doi:10.1111/j.1365-2427.2006.01636.x

Cited by 61 publications

(65 citation statements)

References 17 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Both effects are reflected in the decreasing value of l e /l. Many previous studies characterized reconfiguration of aquatic vegetation through changes in the drag coefficient, 44 for which the total drag is, Blade posture in flow is governed by two parameters. The Cauchy number, Ca, describes the ratio of the drag force to the restoring force due to rigidity.…”

Section: Reconfiguration and Skewness In A Model Seagrassmentioning

confidence: 99%

Strong and weak, unsteady reconfiguration and its impact on turbulence structure within plant canopies

et al. 2014

View full text Add to dashboard Cite

Numerical evaluation of tree canopy shape near noise barriers to improve downwind shielding J. Acoust. Soc. Am. 123, 648 (2008); 10.1121/1.2828052 This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation. Flexible terrestrial and aquatic plants bend in response to fluid motion and this reconfiguration mechanism reduces drag forces, which protects against uprooting or breaking under high winds and currents. The impact of reconfiguration on the flow can be described quantitatively by introducing a drag coefficient that decreases as a power-law function of velocity with a negative exponent known as the Vogel number. In this paper, two case studies are conducted to examine the connection between reconfiguration and turbulence dynamics within a canopy. First, a flume experiment was conducted with a model seagrass meadow. As the flow rate increased, both the mean and unsteady one-dimensional linear elastic reconfiguration increased. In the transition between the asymptotic regimes of negligible and strong reconfiguration, there is a regime of weak reconfiguration, in which the Vogel number achieved its peak negative value. Second, large-eddy simulation was conducted for a maize canopy, with different modes of reconfiguration characterized by increasingly negative values of the Vogel number. Even though the mean vertical momentum flux was constrained by field measurements, changing the mode of reconfiguration altered the distribution, strength, and fraction of momentum carried by strong and weak events. Despite the differences between these two studies, similar effects of the Vogel number on turbulence dynamics were demonstrated. In particular, a more negative Vogel number leads to a more positive peak of the skewness of streamwise velocity within the canopy, which indicates a preferential penetration of strong events into a vegetation canopy. We consider different reconfiguration geometry (one-and two-dimensional) and regime (negligible, weak, and strong) that can apply to a wide range of terrestrial and aquatic canopies. C 2014 AIP Publishing LLC.

show abstract

Section: Reconfiguration and Skewness In A Model Seagrassmentioning

confidence: 99%

Strong and weak, unsteady reconfiguration and its impact on turbulence structure within plant canopies

et al. 2014

View full text Add to dashboard Cite

show abstract

“…It can also be frontal surface area, either estimated from body length and width (Waringer 1993;Asaeda et al 2005;Green 2005) or directly measured on photographs using image analysis procedures (Gaylord et al 1994;Niklas and Spatz 2000;Suren et al 2000;Rudnicki et al 2004;Boller andCarrington 2006, 2007;O'Hare et al 2007). As previously discussed (Alexander 1990;Statzner et al 2006), C d values obtained for these differently estimated reference areas are not comparable.…”

mentioning

confidence: 68%

“…For instance, ecologists currently have an increasing interest in quantifying and comparing (across shapes) drag, acting on organisms living in moving viscous fluids such a sea waves (Gaylord et al 1994), lotic freshwater (Suren et al 2000;Sagnes and Statzner 2009), or air (Rudnicki et al 2004). This interest is particularly witnessed through the recent debate about the quantification of the body shape of flexible freshwater macrophytes in drag parameterizations (Sand-Jensen 2003Green 2005;Sukhodolov 2005;Statzner et al 2006).…”

mentioning

confidence: 99%

“…However, it is not always possible to place the camera at a sufficient distance from the object without reducing the accuracy of subsequent image analyses. For instance, underwater studies (e.g., Statzner et al 2006) have to deal with decreasing water transparency (presence of air bubbles, etc.) when the distance between studied objects and camera increases.…”

mentioning

confidence: 99%

“…Estimating C d values of flexible bodies across different flows, the projected frontal surface area (A f ) captures flow-induced shape variation and is seemingly the most realistic physical description (see Sukhodolov 2005;Boller and Carrington 2006;Statzner et al 2006). In addition, this reference area provides C d estimates that are comparable with those measured for rigid objects, for which C d values are commonly defined relative to their projected frontal area (Vogel 1994).…”

mentioning

confidence: 99%

See 2 more Smart Citations

Using multiple scales to estimate the projected frontal surface area of complex three‐dimensional shapes such as flexible freshwater macrophytes at different flow conditions

Sagnes¹

2010

Limnology & Ocean Methods

Self Cite

View full text Add to dashboard Cite

For different purposes, the projected frontal surface area (A f ) of various organisms is often measured through image analysis. Such A f estimates are particularly used to assess the drag coefficient (C d ) in hydro-or aerodynamic studies of organisms. So far, estimates of A f from image analysis were generally biased (as subsequent C d assessments) for flexible organisms at a given flow, as these estimates were obtained using the same scale for parts of the body being close to or far from the camera. To assess this problem, I used image analyses on 3 flexible freshwater macrophytes, each exposed to 3 different flows. For these, using a single image scale resulted iñ 20% errors of A f estimates if compared with a multiple scale (16 subscales, providing the "reference area") assessment. Using 4 subscales and a human-controlled plant contour definition for A f estimates was a good trade-off between accuracy of A f estimates (error < 3% if compared with the reference area) and analysis effort (6 to 10 min for 1 plant in 1 flow condition). In comparison, using an automated definition of the plant contour (through computer software) and a composite scale (i.e., the mean of the 4 previous subscales) provided slightly worse A f estimates (error < 5% if compared with the reference area). Using the automatic procedure reduced the time to estimate A f for 1 plant in 1 flow condition by ~30%. Therefore, future studies requiring accurate A f assessments of flexible, complex, and elongated bodies should use an appropriate number of subscales as reference.

show abstract

Modeling the flow resistance of woody vegetation using physically based properties of the foliage and stem

2014

View full text Add to dashboard Cite

[1] Both the foliage and stem essentially influence the flow resistance of woody plants, but their different biomechanical properties complicate the parameterization of foliated vegetation for modeling. This paper investigates whether modeling of flow resistance caused by natural woody vegetation can be improved using explicit description of both the foliage and stem. For this purpose, we directly measured the drag forces of Alnus glutinosa, Betula pendula, Salix viminalis, and Salix x rubens twigs in a laboratory flume at four foliation levels, parameterized with the leaf-area-to-stem-area ratio A L /A S . The species differed in the foliage drag but had approximately equal stem drag. For the foliated twigs, increasing A L /A S was found to increase the reconfiguration and the share of the foliage drag to the total drag. The experiments provided new insight into the factors governing the flow resistance of natural woody vegetation and allowed us to develop a model for estimating the vegetative friction factor using the linear superposition of the foliage and stem drag. The model is novel in that the foliage and stem are separately described with physically based parameters: drag coefficients, reconfiguration parameters, and leaf area and frontalprojected stem area per ground area. The model could satisfactorily predict the flow resistance of twig to sapling-sized specimens of the investigated species at velocities of 0.05-1 m/s. As a further benefit, the model allows exploring the variability in drag and reconfiguration associated with differing abundance of the foliage in relation to the stem.Citation: V€ astil€ a, K., and J. J€ arvel€ a (2014), Modeling the flow resistance of woody vegetation using physically based properties of the foliage and stem, Water Resour. Res., 50,[229][230][231][232][233][234][235][236][237][238][239][240][241][242][243][244][245]

show abstract

The debate about drag and reconfiguration of freshwater macrophytes: comparing results obtained by three recently discussed approaches

Cited by 61 publications

References 17 publications

Strong and weak, unsteady reconfiguration and its impact on turbulence structure within plant canopies

Strong and weak, unsteady reconfiguration and its impact on turbulence structure within plant canopies

Using multiple scales to estimate the projected frontal surface area of complex three‐dimensional shapes such as flexible freshwater macrophytes at different flow conditions

Modeling the flow resistance of woody vegetation using physically based properties of the foliage and stem

Contact Info

Product

Resources

About