Laboratory Investigation of Mean Drag in a Random Array of Rigid, Emergent Cylinders

Tanino, Yukie; Nepf, Heidi

doi:10.1061/(asce)0733-9429(2008)134:1(34)

Cited by 392 publications

(379 citation statements)

References 23 publications

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“…Huang et al (2011) determined drag coefficient on a basis of own experiments with a solitary wave propagating over a vegetation model made of rigid cylinders of varying aligned and staggered arrangement. The results were completed by experimental data by Tanino and Nepf (2008), obtained for randomly arranged cylinders. Similar to the work by Harada and Imamura (2001), the drag coefficient was also expressed in terms of the submerged volume ratio:…”

Section: Flow Resistance Of Single Mangrove Models Under Solitary Wavmentioning

confidence: 99%

Tsunami damping by mangrove forest: a laboratory study using parameterized trees

Strusińska-Correia¹,

Husrin

Oumeraci

2013

Nat. Hazards Earth Syst. Sci.

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Tsunami attenuation by coastal vegetation was examined under laboratory conditions for mature mangroves Rhizophora sp. The developed novel tree parameterization concept, accounting for both bio-mechanical and structural tree properties, allowed to substitute the complex tree structure by a simplified tree model of identical hydraulic resistance. The most representative parameterized mangrove model was selected among the tested models with different frontal area and root density, based on hydraulic test results. The selected parameterized tree models were arranged in a forest model of different width and further tested systematically under varying incident tsunami conditions (solitary waves and tsunami bores). The damping performance of the forest models under these two flow regimes was compared in terms of wave height and force envelopes, wave transmission coefficient as well as drag and inertia coefficients. Unlike the previous studies, the results indicate a significant contribution of the foreshore topography to solitary wave energy reduction through wave breaking in comparison to that attributed to the forest itself. A similar rate of tsunami transmission (ca. 20%) was achieved for both flow conditions (solitary waves and tsunami bores) and the widest forest (75 m in prototype) investigated. Drag coefficient CD attributed to the solitary waves tends to be constant (CD = 1.5) over the investigated range of the Reynolds number

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Section: Flow Resistance Of Single Mangrove Models Under Solitary Wavmentioning

confidence: 99%

Tsunami damping by mangrove forest: a laboratory study using parameterized trees

Strusińska-Correia¹,

Husrin

Oumeraci

2013

Nat. Hazards Earth Syst. Sci.

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“…Dean and Bender (2006) used linear wave theory to show that wave damping over vegetated areas had a significant effect on the static wave setup, where the vegetation was represented by emergent cylinders. The attenuation of uni-directional flow within vegetation has been well documented (Mazda et al 1997;Nepf 1999;Leonard and Reed 2002;Tanino and Nepf 2008).…”

Section: Previous Studiesmentioning

confidence: 99%

Wave Damping in Reed: Field Measurements and Mathematical Modeling

Lövstedt

Larson

2010

J. Hydraul. Eng.

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Wave damping in vegetation in shallow lakes reduces resuspension and thereby improves the light climate and decreases nutrient recycling. In this study, wave transformation in reed (Phragmites australis) was measured in a shallow lake. Theoretical models of wave height decay, based on linear wave theory, and transformation of the probability density function, using a wave-by-wave approach, were developed and compared to the collected data. Field data showed an average decrease in wave height of 4-5% m -1 within the first 5-14 m of the vegetation. Incident root-mean-square wave height varied between 1 and 8 cm, which is typical for the studied lake. A species-specific drag coefficient, C D , was found to be about 9 (most probable range: 3-25), and the model was relatively insensitive to moderate variations in this parameter. The coefficient showed little correlation with aReynolds number or a Keulegan-Carpenter number. The probability density function for the wave height did not change significantly, but for longer distances into the vegetation and higher incident waves it tended to be less similar to a Rayleigh distribution and more similar to the theoretically developed transformed distribution, where the higher waves are more damped than the smaller. Relationships developed in this study can be employed for management purposes to reduce resuspension and erosion in shallow lakes.

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“…and Ball et al [3] assumed c D = 1 for simplicity, while Chen et al [2] estimated c D for each pile arrangement by assuming that the local drag is proportional to the solid volume fraction φ of the array [20]. All of the experimental results plotted in figure 6a are for configurations where φ < 0.…”

Section: Example Applications (A) Prediction Of Core Flow Velocity Thmentioning

confidence: 99%

Flow through a very porous obstacle in a shallow channel

et al. 2017

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A theoretical model, informed by numerical simulations based on the shallow water equations, is developed to predict the flow passing through and around a uniform porous obstacle in a shallow channel, where background friction is important. This problem is relevant to a number of practical situations, including flow through aquatic vegetation, the performance of arrays of turbines in tidal channels and hydrodynamic forces on offshore structures. To demonstrate this relevance, the theoretical model is used to (i) reinterpret core flow velocities in existing laboratory-based data for an array of emergent cylinders in shallow water emulating aquatic vegetation and (ii) reassess the optimum arrangement of tidal turbines to generate power in a tidal channel. Comparison with laboratory-based data indicates a maximum obstacle resistance (or minimum porosity) for which the present theoretical model is valid. When the obstacle resistance is above this threshold the shallow water equations do not provide an adequate representation of the flow, and the theoretical model over-predicts the core flow passing through the obstacle. The second application of the model confirms that natural bed resistance increases the power extraction potential for a partial tidal fence in a shallow channel and alters the optimum arrangement of turbines within the fence.

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Laboratory Investigation of Mean Drag in a Random Array of Rigid, Emergent Cylinders

Cited by 392 publications

References 23 publications

Tsunami damping by mangrove forest: a laboratory study using parameterized trees

Tsunami damping by mangrove forest: a laboratory study using parameterized trees

Wave Damping in Reed: Field Measurements and Mathematical Modeling

Flow through a very porous obstacle in a shallow channel

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