scholarly journals Wave Height Attenuation and Flow Resistance Due to Emergent or Near-Emergent Vegetation

Water ◽  
2018 ◽  
Vol 10 (4) ◽  
pp. 402 ◽  
Author(s):  
Paolo Peruzzo ◽  
Francesca De Serio ◽  
Andrea Defina ◽  
Michele Mossa
Keyword(s):  
Wave Height ◽  
Flow Resistance ◽  
Emergent Vegetation ◽  
Wave Height Attenuation

scholarly journals LABORATORY SIMULATIONS OF WAVE ATTENUATION BY AN EMERGENT VEGETATION OF ARTIFICIAL PHRAGMITES AUSTRALIS: AN EXPERIMENTAL STUDY OF AN OPEN-CHANNEL WAVE FLUME

2015 ◽  
Vol 23 (4) ◽  
pp. 251-266 ◽  
Author(s):  
Li YIPING ◽  
Desmond Ofosu ANIM ◽  
Ying WANG ◽  
Chunyang TANG ◽  
Wei DU ◽  
...  
Keyword(s):  
Experimental Study ◽  
Phragmites Australis ◽  
Wave Height ◽  
Plant Density ◽  
Wave Attenuation ◽  
Emergent Vegetation ◽  
Irregular Waves ◽  
Shore Protection ◽  
Near Shore ◽  
Wave Conditions

This paper presents a well-controlled laboratory experimental study to evaluate wave attenuation by artificial emergent plants (Phragmites australis) under different wave conditions and plant stem densities. Results showed substantial wave damping under investigated regular and irregular wave conditions and also the different rates of wave height and within canopy wave-induced flows as they travelled through the vegetated field under all tested conditions. The wave height decreased by 6%–25% at the insertion of the vegetation field and towards the downstream at a mean of 0.2 cm and 0.32 cm for regular and irregular waves respectively. The significant wave height along the vegetation field ranged from 0.89–1.76 cm and 0.8–1.28 cm with time mean height of 1.38 cm and 1.11 cm respectively for regular and irregular waves. This patterns as affected by plant density and also location from the leading edge of vegetation is investigated in the study. The wave energy attenuated by plant induced friction was predicted in terms of energy dissipation factor (fe) by Nielsen’s (1992) empirical model. Shear stress as a driving force of particle resuspension and the implication of the wave attenuation on near shore protection from erosion and sedimentation was discussed. The results and findings in this study will advance our understanding of wave attenuation by an emergent vegetation of Phragmites australis, in water system engineering like near shore and bank protection and restoration projects and also be employed for management purposes to reduce resuspension and erosion in shallow lakes.

scholarly journals Wave energy dissipation in the mangrove vegetation off Mumbai, India

2017 ◽  
Author(s):  
Samiksha S. Volvaiker ◽  
Ponnumony Vethamony ◽  
Prasad K. Bhaskaran ◽  
Premanand Pednekar ◽  
MHamsa Jishad ◽  
...  
Keyword(s):  
Energy Dissipation ◽  
Drag Coefficient ◽  
Wave Height ◽  
Wave Attenuation ◽  
Coastal Region ◽  
Measured Data ◽  
Vegetation Density ◽  
Mangrove Vegetation ◽  
Wave Height Attenuation ◽  
Set Up

Abstract. Coastal regions of India are prone to sea level rise, cyclones, storm surges and human induced activities, resulting in flood, erosion, and inundation. The primary aim of the study is to estimate wave attenuation by mangrove vegetation using SWAN model in standalone mode, as well as SWAN nested with WW3 model for the Mumbai coastal region. To substantiate the model results, wave measurements were carried out during 5–8 August 2015 at 3 locations in a transect normal to the coast using surface mounted pressure level sensors under spring tide conditions. The measured data presents wave height attenuation of the order of 52 %. The study shows a linear relationship between wave height attenuation and gradual changes in water level in the nearshore region, in phase with the tides. Model set-up and sensitivity analyses were conducted to understand the model performance to vegetation parameters. It was observed that wave attenuation increased with an increase in drag coefficient (Cd), vegetation density, and stem diameter. For a typical set-up for Mumbai coastal region having vegetation density of 0.175 per m2, stem diameter of 0.3 m and drag coefficient varying from 0.4 to 1.5, the model reproduced attenuation, ranging from 49 to 55 %, which matches well with the measured data. Spectral analysis performed for the cases with and without vegetation very clearly portrays energy dissipation in the vegetation area as well as spectral changes. This study has the potential of improving the quality of wave prediction in vegetation areas, especially during monsoon season and extreme weather events.

Flow Resistance of Emergent Vegetation

2004 ◽  
Author(s):  
Brian D. Barkdoll ◽  
Sandeep Vittilam ◽  
Sean J. Bennett ◽  
Carlos V. Alonso
Keyword(s):  
Flow Resistance ◽  
Emergent Vegetation

Investigation of flow resistance exerted by rigid emergent vegetation in open channel

2019 ◽  
Vol 67 (3) ◽  
pp. 971-986 ◽  
Author(s):  
Antonino D’Ippolito ◽  
Agostino Lauria ◽  
Giancarlo Alfonsi ◽  
Francesco Calomino
Keyword(s):  
Flow Resistance ◽  
Open Channel ◽  
Emergent Vegetation ◽  
Rigid Emergent Vegetation

scholarly journals FLOW DYNAMICS OF WAVES PROPAGATING OVER DIFFERENT PERMEABLE BEDS

2017 ◽  
pp. 35
Author(s):  
Sara Corvaro ◽  
Alessandro Mancinelli ◽  
Maurizio Brocchini
Keyword(s):  
Shear Stress ◽  
Flow Resistance ◽  
Single Layer ◽  
Coastal Engineering ◽  
Flow Dynamics ◽  
Bottom Shear Stress ◽  
Natural Stones ◽  
Wave Height Attenuation ◽  
Rough Beds ◽  
Good Agreement

The analysis of the hydrodynamics over porous media is of interest for many coastal engineering applications as the wave propagation over permeable structures or gravel beaches. The study of a boundary layer evolving over permeable beds is important to a better understanding of the interactions between the flow over and inside the porous medium. An experimental study has been performed to analyze the dynamics produced when waves propagate over two kinds of permeable beds: spheres (regular permeability) and natural stones. For comparative purposes the same analysis has been extended to two rough beds made, respectively, by a single layer of spheres and natural stones. We here focus on the correlation between the wave energy reduction induced by a porous bed and the flow resistance. An experimental law for the prediction of the friction factor is found by using the log-fit method in analogy to that reported in Dixen et al. (2008) for rough beds. Moreover, inspection of the turbulent velocity components allows one to evaluate the bottom shear stress. The latter analysis has been performed for different permeable beds (regular and irregular beds). A good agreement between the bottom shear stress behavior and the wave height attenuation over rough and permeable beds (Corvaro et al. 2010 and Corvaro et al. 2014a) has been observed.

scholarly journals The Maximum Height and Attenuation of Impulse Waves Generated by Subaerial Landslides

2018 ◽  
Vol 2018 ◽  
pp. 1-14 ◽  
Author(s):  
Baoliang Wang ◽  
Lingkan Yao ◽  
Haixin Zhao ◽  
Cong Zhang
Keyword(s):  
Influencing Factors ◽  
Wave Height ◽  
Water Waves ◽  
High Speed ◽  
Transient Flow ◽  
Evaluation Criteria ◽  
Maximum Height ◽  
Flume Experiments ◽  
Orthogonal Experiments ◽  
Wave Height Attenuation

High-speed landslides that flow into reservoirs can cause impulsive water waves. To study the characteristics of the maximum impulse wave’s height and its attenuation, 25 sets of flume experiments were conducted using orthogonal theory and 6 main influencing factors were considered. Taking the impulse wave heights as the evaluation criteria and analyzing the 6 influencing factors at 5 different levels, the characteristics of the maximum impulse wave’s height and its attenuations were obtained. Then, statistical relationships between the maximum wave height and the controlling factors were proposed. Then, by combining the continuity equation and the hydrodynamic open channel transient flow movement equation, the process of landslide wave height attenuation was studied, and it was found that the attenuation of the wave is consistent with exponential attenuation. Then, combined with the data obtained from the orthogonal experiments, an attenuation equation for the surge was derived. Finally, the proposed equation was validated by applying it to the landslides that took place along the shore of the Zipingpu reservoir, which were triggered by the Wenchuan earthquake, and the results indicate that the calculated results are very close to the observed results.

scholarly journals ENERGY LOSSES UNDER WAVE ACTION

1970 ◽  
Vol 1 (12) ◽  
pp. 16 ◽  
Author(s):  
P.D. Treloar ◽  
A. Brebner
Keyword(s):  
Boundary Layer ◽  
Energy Dissipation ◽  
Wave Height ◽  
Dissipation Function ◽  
Wave Action ◽  
Energy Losses ◽  
Boundary Layer Equations ◽  
Wave Height Attenuation ◽  
Prandtl Boundary Layer ◽  
Made In

Wave-height attenuation measurements were made in two identical flumes of different widths and the results used to separate bottom energy losses from sidewall energy losses These energy losses, in the form of rates of energy dissipation, were then compared with their theoretical values as calculated by solving the linearized Prandtl boundary layer equations and evaluating the Rayleigh dissipation function Using these results, an adjusted formula for the wave-height attenuation modulus was determined.

scholarly journals Wave energy dissipation in the mangrove vegetation off Mumbai, India

2018 ◽  
Author(s):  
Samiksha S. Volvaiker ◽  
Ponnumony Vethamony ◽  
Prasad K. Bhaskaran ◽  
Premanand Pednekar ◽  
Mhamsa Jishad ◽  
...  
Keyword(s):  
Energy Dissipation ◽  
Drag Coefficient ◽  
Wave Height ◽  
Wave Energy ◽  
Coastal Region ◽  
Measured Data ◽  
Vegetation Density ◽  
Mangrove Vegetation ◽  
Wave Height Attenuation ◽  
Set Up

Abstract. Coastal regions of India are prone to sea level rise, cyclones, storm surges and human induced activities, resulting in flood, erosion and inundation. The primary aim of the study is to estimate wave energy attenuation by mangrove vegetation using SWAN model, and validate the model results with measurements for the Mumbai coastal region. Wave measurements were carried out during 5–8 August 2015 at 3 locations in a transect normal to the coast using surface mounted pressure level sensors in spring tide conditions. The measured data presents wave height attenuation of the order of 52 %. The study shows a linear relationship between wave height attenuation and gradual changes in water level in the nearshore region, in phase with the tides. Model set-up and sensitivity analyses were conducted to understand the model performance to vegetation parameters. It was observed that wave attenuation increases with an increase in drag coefficient, vegetation density and stem diameter. For a typical set-up for Mumbai coastal region having vegetation density of 0.175 per m2, stem diameter of 0.3 m and drag coefficient varying from 0.4 to 1.5, the model reproduced attenuation, ranging from 49 to 55 %, which matches well with the measured data. Spectral analysis performed for the cases with and without vegetation very clearly portrays energy dissipation in the vegetation area. This study has the potential of improving the quality of wave prediction in vegetation areas, especially during monsoon season and extreme weather events.

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