Influence of Blade Flexibility on the Drag Coefficient of Aquatic Vegetation

Houser, Chris; Trimble, Sarah; Morales, Bradley

doi:10.1007/s12237-014-9840-3

Cited by 51 publications

(44 citation statements)

References 23 publications

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“…The variable C D approaches required modifications to the SWAN source code to compute C D based on the Keulegan–Carpenter number. Model runs using variable C D expressions from Mendez and Losada (), Bradley and Houser (), Sánchez‐González et al (), and Houser et al () were compared to the field data. The formulation of Sánchez‐González et al (), who carried out flume experiments on artificial P. oceanica (a Mediterranean seagrass) meadows, best reproduced the observed wave characteristics ( H s , T m , and

ϵ

) during the late May northward wind event and was selected to compare against the constant C D approach in Run 4.…”

Section: Methodsmentioning

confidence: 99%

Spectral wave dissipation by submerged aquatic vegetation in a back‐barrier estuary

Nowacki

Beudin

Ganju

2017

Limnology & Oceanography

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Submerged aquatic vegetation is generally thought to attenuate waves, but this interaction remains poorly characterized in shallow-water field settings with locally generated wind waves. Better quantification of wave-vegetation interaction can provide insight to morphodynamic changes in a variety of environments and also is relevant to the planning of nature-based coastal protection measures. Toward that end, an instrumented transect was deployed across a Zostera marina (common eelgrass) meadow in Chincoteague Bay, Maryland/Virginia, U.S.A., to characterize wind-wave transformation within the vegetated region. Field observations revealed wave-height reduction, wave-period transformation, and wave-energy dissipation with distance into the meadow, and the data informed and calibrated a spectral wave model of the study area. The field observations and model results agreed well when local wind forcing and vegetation-induced drag were included in the model, either explicitly as rigid vegetation elements or implicitly as large bed-roughness values. Mean modeled parameters were similar for both the explicit and implicit approaches, but the spectral performance of the explicit approach was poor compared to the implicit approach. The explicit approach over-predicted low-frequency energy within the meadow because the vegetation scheme determines dissipation using mean wavenumber and frequency, in contrast to the bed-friction formulations, which dissipate energy in a variable fashion across frequency bands. Regardless of the vegetation scheme used, vegetation was the most important component of wave dissipation within much of the study area. These results help to quantify the influence of submerged aquatic vegetation on wave dynamics in future model parameterizations, field efforts, and coastal-protection measures. In the aforementioned studies, local (re-) generation of waves was not considered. However, in limited-fetch environments like back-barrier lagoons, local winds are critical to the wave field, the resulting bed stress, sediment transport, and ultimately the character of the local geomorphology. In addition to measuring bulk quantities like significant wave height, wave period, and wave dissipation in vegetated regions, a full quantification of the spectral wave field is crucial to understanding the wave dynamics and potential feedbacks between seagrass, sediment transport, and light availability.Wave-vegetation interaction models generally characterize vegetation as rigid cylinders with a constant drag Limnol. Oceanogr. 62, 2017, 736-753

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ϵ

) during the late May northward wind event and was selected to compare against the constant C D approach in Run 4.…”

Section: Methodsmentioning

confidence: 99%

Spectral wave dissipation by submerged aquatic vegetation in a back‐barrier estuary

Nowacki

Beudin

Ganju

2017

Limnology & Oceanography

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“…Under oscillatory flows, the hydrodynamics of incident flow conditions become increasingly important as wave period and frequency can often force the plant to flex in or out of phase with the incoming wave (dynamic reconfiguration) . The plant can, therefore, move passively with the wave or alternatively generate resistance by moving more slowly or in the opposing direction to the wave . Bouma et al observed that a stiff salt marsh grass was three times more effective at dissipating waves than a relatively flexible seagrass.…”

Section: The Influence Of Vegetation Structure and Plant Mechanical Pmentioning

confidence: 99%

“…Swaying of vegetation in response to oscillatory flows is sometimes incorporated through an additional drag coefficient or by modifying the approach velocity . These empirically derived models have also been incorporated into more complex 2D/3D numerical modeling software such as SWAN‐VEG and DELFT‐3D …”

Section: The Influence Of Vegetation Structure and Plant Mechanical Pmentioning

confidence: 99%

A review of plant‐flow interactions on salt marshes: the importance of vegetation structure and plant mechanical characteristics

2015

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Observations of plant-flow interactions on salt marshes have revealed a highly complex process dominated by the tightly coupled effects of plant characteristics and hydrodynamic conditions. This paper highlights the importance of vegetation structures such as plant density and height, as well as their spatial variability and mechanical properties including flexibility, upon energy dissipation and flow modification. Many field, laboratory and modeling studies which attempt to predict flow dissipation or improve our understanding of plant-flow interactions use simplified structural measures of salt marsh vegetation or artificial representations. These simplifications neglect important plant and canopy elements and are unlikely to be truly representative of their natural counterparts. Such approaches limit our understanding of plant-flow interactions and potentially compromise the predictive accuracy and application of numerical flow models. It is important therefore that improved techniques to measure vegetation structure are adopted in order to better define the key relationships between measurable plant characteristics and dragrelevant plant properties.

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“…To provide a predictive estimation of wave attenuation, the bulk drag coefficient is typically defined as a function of nondimensional flow parameters, either the stem Reynolds or Keulegan-Carpenter number (Kobayashi et al, 1993;Ozeren et al, 2014;Houser et al, 2015; among many others). The reasoning for selecting either the Reynolds or Keulegan-Carpenter is largely statistical and switches throughout the literature.…”

Section: Parameters Rolesmentioning

confidence: 99%

“…The reasoning for selecting either the Reynolds or Keulegan-Carpenter is largely statistical and switches throughout the literature. Houser et al (2015) suggests that the decision to use one over the other does not necessarily improve the description of the physical processes …”

Section: Parameters Rolesmentioning

confidence: 99%

Engineering with Nature to Reduce Wave Energy in Wetlands

Smith¹,

Bryant²

2017

Handbook of Coastal and Ocean Engineering

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A body of literature quantifying wave attenuation through vegetation has developed within the last few decades and serves as the foundation for growing interest in wetlands for engineering with nature applications. Wave dissipation is shown to be highly variable, influenced by hydrodynamics, plant structure, and the interaction between the two. The current method of predicting wave dissipation often makes use of an empirical drag coefficient, which is given as a function of nondimensional flow parameter. These empirical equations are shown to have limitations, particularly in the transition from the submerged to emergent regime, and are highly variable in nature and in magnitude. Vegetation is shown to preferentially dissipate energy at frequencies higher than the spectral peak for single-and double-peaked wave spectra. Idealized simulations of Jamaica Bay with STeady-state spectral WAVE (STWAVE) demonstrate the potential for vegetation to provide shoreline protection by reducing wave height under severe wind and water level conditions.

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Influence of Blade Flexibility on the Drag Coefficient of Aquatic Vegetation

Cited by 51 publications

References 23 publications

Spectral wave dissipation by submerged aquatic vegetation in a back‐barrier estuary

Spectral wave dissipation by submerged aquatic vegetation in a back‐barrier estuary

A review of plant‐flow interactions on salt marshes: the importance of vegetation structure and plant mechanical characteristics

Engineering with Nature to Reduce Wave Energy in Wetlands

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