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

Peruzzo, Paolo; Serio, Francesca De; Defina, Andrea; Mossa, Michele

doi:10.3390/w10040402

Cited by 33 publications

(14 citation statements)

References 50 publications

(70 reference statements)

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“…These methods may be costly for developing countries because of significant capital investment requirements [18]. Currently, ecological, natural methods are widely considered in many developed and underdeveloped countries [19][20][21][22][23]. Ecosystem degradation is a major cause of increasing water resources management challenges [24][25][26][27][28].…”

Section: Introductionmentioning

confidence: 99%

Experimental Investigation of Flood Energy Dissipation by Single and Hybrid Defense System

Ahmed

Ghumman

2019

Water

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In this study, a series of laboratory experiments were conducted to investigate the energy loss through the hybrid defense system (HDS) in the order of dike, moat, and emergent vegetation in steady subcritical flow conditions. The results of HDS were compared with a single defense system (SDS) comprising only vegetation (OV). The dimensions of dike were kept constant while two different shapes (trapezoidal and rectangular) of moat were considered. The impacts of vegetation of variable thickness and density were investigated. Two combinations of HDS were investigated including the combination of dike and vegetation (DV) and the combination of dike, moat, and vegetation (DMV). The effect of backwater rise due to the vegetation, hydraulic jump formation and the impact of the arrival time of floodwater on energy dissipation were investigated. It was observed that on the upstream side of obstructions, the backwater depth increased by increasing the Froude number in both the SDS and HDS. The hydraulic jump observed in HDS was classified and the energy dissipation due to it was calculated. Under various conditions investigated in this paper, the maximum average energy dissipation was 32% in SDS and 46% in HDS. The trapezoidal moat performed better than rectangular moat as energy dissipater. The delay time was also greater with trapezoidal moat as compared to that in rectangular one. The maximum delay time was 140 s in the case of HDS. Hence, the hybrid defense system offered maximum resistance to the flow of water, thus causing a significant energy loss. For each case of SDS and HDS, empirical equations were developed by regression analysis to estimate the energy dissipation amounts.

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Section: Introductionmentioning

confidence: 99%

Experimental Investigation of Flood Energy Dissipation by Single and Hybrid Defense System

Ahmed

Ghumman

2019

Water

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“…Classical approaches to detect and follow free surfaces are based on surface piercing wave gauges [20][21][22][23][24][25] or ultrasonic/acoustic probes, which measure the delay of the ultrasonic signal echo caused by the density change at the free surface [26,27]. Submerged acoustic instruments can measure the fluid velocity beneath the free surface at laboratory scale [28,29] as well as for field applications [30].…”

Section: Introductionmentioning

confidence: 99%

Capturing the Motion of the Free Surface of a Fluid Stored within a Floating Structure

Gabl

Steynor

Forehand

et al. 2018

Water

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Large floating structures, such as liquefied natural gas (LNG) ships, are subject to both internal and external fluid forces. The internal fluid forces may also be detrimental to a vessel’s stability and cause excessive loading regimes when sloshing occurs. Whilst it is relatively easy to measure the motion of external free surface with conventional measurement techniques, the sloshing of the internal free surface is more difficult to capture. The location of the internal free surface is normally extrapolated from measuring the pressure acting on the internal walls of the vessel. In order to understand better the loading mechanisms of sloshing internal fluids, a method of capturing the transient inner free surface motion with negligible affect on the response of the fluid or structure is required. In this paper two methods will be demonstrated for this purpose. The first approach uses resistive wave gauges made of copper tape to quantify the water run-up height on the walls of the structure. The second approach extends the conventional use of optical motion tracking to report the position of randomly distributed free floating markers on the internal water surface. The methods simultaneously report the position of the internal free surface with good agreement under static conditions, with absolute variation in the measured water level of around 4 mm. This new combined approach provides a map of the free surface elevation under transient conditions. The experimental error is shown to be acceptable (low mm-range), proving that these experimental techniques are robust free surface tracking methods in a range of situations.

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“…Nevertheless, rigid cylinder models can be considered qualitatively effective for simulating the cross-section scale effects on the turbulence structure and describing morphodynamic processes of channels with vegetated floodplains [13]. Because of the practical importance of modeling turbulence in natural watercourses and coastal wetlands, an increasing interest in describing the turbulent flow structure in vegetated flows [14][15][16], highly rough beds, and obstructed flows [17] is noticeable.…”

Section: Introductionmentioning

confidence: 99%

Vegetated Channel Flows: Turbulence Anisotropy at Flow–Rigid Canopy Interface

et al. 2018

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This laboratory study aimed at investigating the mean and turbulent characteristics of a densely vegetated flow by testing four different submergence ratios. The channel bed was covered by a uniform array of aligned metallic cylinders modeling rigid submerged vegetation. Instantaneous velocities, acquired with a three-component acoustic Doppler velocimeter (ADV), were used to analyze the mean and turbulent flow structure. The heterogeneity of the flow field was described by the distributions of mean velocities, turbulent intensities, skewness, kurtosis, Reynolds stresses, and Eulerian integral scales. The exchange processes at the flow-vegetation interface were explored by applying the turbulence triangle technique, a far less common technique for vegetated flows based on the invariant maps of the anisotropic Reynolds stress tensor.which reflects, to a large extent, the presence of organized motions. Indeed, the anisotropic Reynolds stress component is the only part of the total stress responsible for the momentum transport [22], and, therefore, its study is crucial for the understanding and modeling of turbulence in vegetated flows.The anisotropy pattern within the flow domain can be investigated using the technique of the anisotropy invariants proposed by Lumley and Newman [23]. This technique, fairly less common for the analysis of vegetated flows, allows for the characterization of the spatial distribution of the anisotropy degree and nature. Only few examples of the application of this methodology are available in the literature, and these mainly refer to numerical and experimental analyses of flows over highly rough beds [24,25].In this study, the turbulent structure of the flow over a submerged array of rigid cylinders was experimentally investigated by coupling the traditional approach based on the spatial distributions of velocity statistics and spectral analysis [5,6,26] with a new methodology adopted for providing the overall description of the turbulence anisotropy, represented by the turbulence triangles [27]. Specifically, the effects of the variability of the submergence, that is, the ratio between the uniform flow depth and the cylinder's height, on the mean velocity profiles, the distributions of higher-order velocity statistics, quadrant analysis, and the distribution of integral time and length scales were analyzed with reference to the anisotropy pattern resulting from the invariant maps. Materials and Methods Laboratory FlumeThe experiments were carried out in an 8 m long, 0.4 m wide, and 0.4 m high Plexiglas-walled recirculating flume in the Laboratory of Hydraulics and Hydraulic Structures at the University of Naples Federico II (Figure 1a). The channel was supplied by a 4.5 m 3 tank into which water was led through the water supply system of the laboratory from a water tower. Specifically, in order to stabilize flow rates in the channel, water was not directly pumped into the flume but, from the recirculating system reservoir, was led to a water tower with a pumping station.The discharge w...

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

Cited by 33 publications

References 50 publications

Experimental Investigation of Flood Energy Dissipation by Single and Hybrid Defense System

Experimental Investigation of Flood Energy Dissipation by Single and Hybrid Defense System

Capturing the Motion of the Free Surface of a Fluid Stored within a Floating Structure

Vegetated Channel Flows: Turbulence Anisotropy at Flow–Rigid Canopy Interface

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