Bed Roughness Effects on the Turbulence Characteristics of Flows through Emergent Rigid Vegetation

Penna, Nadia; Coscarella, Francesco; D’Ippolito, Antonino; Gaudio, Roberto

doi:10.3390/w12092401

Cited by 19 publications

(34 citation statements)

References 59 publications

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“…Experimental studies of velocity profiles, like those shown in Figures 3-5, are of much interest; in some cases also the shear stress profiles are studied by means of velocity fluctuant components and Reynolds stress theory [19,[107][108][109][110][111].…”

Section: Methodsmentioning

confidence: 99%

“…The author gives, for every class of channels, the minimum, average, and maximum values of Manning n coefficient, warning that when the channel is artificial, the average values should be used in case of good maintenance only. In Tables 5 and 6 of Chow's book ( [47], p. [110][111][112][113], one can observe that the Manning coefficient is 0.018 sm −1/3 in case of the excavated channel, straight, clean, uniform cross-section with no vegetation, and 0.035 sm −1/3 in case of dense weeds. In natural streams, its values are 0.030 sm −1/3 when the cross-section is clean, and 0.045 sm −1/3 in case of weeds.…”

Section: Descriptive and Photographic Comparison Approachesmentioning

confidence: 99%

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Flow Resistance in Open Channel Due to Vegetation at Reach Scale: A Review

D’Ippolito

Calomino

Alfonsi

et al. 2021

Water

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Vegetation on the banks and flooding areas of watercourses significantly affects energy losses. To take the latter into account, computational models make use of resistance coefficients based on the evaluation of bed and walls roughness besides the resistance to flow offered by vegetation. This paper, after summarizing the classical approaches based on descriptions and pictures, considers the recent advancements related to the analytical methods relative both to rigid and flexible vegetation. In particular, emergent rigid vegetation is first analyzed by focusing on the methods for determining the drag coefficient, then submerged rigid vegetation is analyzed, highlighting briefly the principles on which the different models are based and recalling the comparisons made in the literature. Then, the models used in the case of both emergent and submerged rigid vegetation are highlighted. As to flexible vegetation, the paper reminds first the flow conditions that cause the vegetation to lay on the channel bed, and then the classical resistance laws that were developed for the design of irrigation canals. The most recent developments in the case of submerged and emergent flexible vegetation are then presented. Since turbulence studies should be considered as the basis of flow resistance, even though the path toward practical use is still long, the new developments in the field of 3D numerical methods are briefly reviewed, presently used to assess the characteristics of turbulence and the transport of sediments and pollutants. The use of remote sensing to map riparian vegetation and estimating biomechanical parameters is briefly analyzed. Finally, some applications are presented, aimed at highlighting, in real cases, the influence exerted by vegetation on water depth and maintenance interventions.

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Section: Methodsmentioning

confidence: 99%

Section: Descriptive and Photographic Comparison Approachesmentioning

confidence: 99%

Flow Resistance in Open Channel Due to Vegetation at Reach Scale: A Review

D’Ippolito

Calomino

Alfonsi

et al. 2021

Water

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“…Recently, Penna et al [18] analyzed the flow field, the turbulent kinetic energy (TKE), and the energy spectra of velocity fluctuations around a rigid stem on three different rough beds. They showed that, in the region below the free surface region, the flow is strongly influenced by the vegetation.…”

Section: Introductionmentioning

confidence: 99%

Anisotropy in the Free Stream Region of Turbulent Flows through Emergent Rigid Vegetation on Rough Beds

Penna

Coscarella

D’Ippolito

et al. 2020

Water

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Most of the existing works on vegetated flows are based on experimental tests in smooth channel beds with staggered-arranged rigid/flexible vegetation stems. Actually, a riverbed is characterized by other roughness elements, i.e., sediments, which have important implications on the development of the turbulence structures, especially in the near-bed flow zone. Thus, the aim of this experimental study was to explore for the first time the turbulence anisotropy of flows through emergent rigid vegetation on rough beds, using the so-called anisotropy invariant maps (AIMs). Toward this end, an experimental investigation, based on Acoustic Doppler Velocimeter (ADV) measures, was performed in a laboratory flume and consisted of three runs with different bed sediment size. In order to comprehend the mean flow conditions, the present study firstly analyzed and discussed the time-averaged velocity, the Reynolds shear stresses, the viscous stresses, and the vorticity fields in the free stream region. The analysis of the AIMs showed that the combined effect of vegetation and bed roughness causes the evolution of the turbulence from the quasi-three-dimensional isotropy to axisymmetric anisotropy approaching the bed surface. This confirms that, as the effects of the bed roughness diminish, the turbulence tends to an isotropic state. This behavior is more evident for the run with the lowest bed sediment diameter. Furthermore, it was revealed that also the topographical configuration of the bed surface has a strong impact on the turbulent characteristics of the flow.

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“…The second review paper [11] deals with the environmental impacts associated with the rapidly growing mariculture industry, while one research paper [12] investigated the flow and concentration patterns downstream an aquaculture cage net panel in parametric flume experiments. Four studies approached the stream and river systems from a variety of perspectives, ranging from the physical modelling of flow with vegetation [13] and the numerical simulation of solute transport in river with dead zones [14], to the laboratory study of flood discharge atomisation [15] and the geomorphic characterisation and classification of a large river [16]. Three contributions are about hyporheic fluxes: two field studies investigated these fluxes at a small river confluence [17] and the effects of such fluxes on the macroinvertebrate community [18], while their relationship with the bioturbation activity of macroinvertebrates was studied in laboratory [19].…”

mentioning

confidence: 99%

“…While studies focused on the flow-plant interaction were mostly performed on smooth channel beds, natural riverbeds are characterised by other roughness elements that also affect flow turbulent structures. As such, Penna et al [13] performed an experimental study on the bed roughness effects on the turbulence characteristics in an open-channel flow with rigid emergent vegetation. The results showed that the flow was strongly influenced by the vegetation in the intermediate layer below the free surface and was affected by a combined effect of vegetation and bed roughness in the near bed layer.…”

mentioning

confidence: 99%