FLOW RESISTANCE OF POSIDONIA OCEANICA IN SHALLOW WATER

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Abstract

Management of coastal waters and lagoons by mathematical circulation models requires determination of the hydraulic resistance of submerged vegetation. A plant typical of sandy coastal bottoms in the Mediterranean Sea is Posidonia oceanica, which is constituted by very thin and flexible ribbon-like leaves, about 1 cm wide and up to 1.5 m long, and usually covers the bottom with a density of 500-1000 plants/ m2. From the hydraulic viewpoint, P. oceanica constitutes a particular roughness, because, as the velocity increases, the leaves bend more and more until they lie down on the bottom. Although P. oceanica is widespread, in the technical literature it is difficult to find indications about flow resistance due to this plant. In this paper, the results of specific experimental research are reported. The runs were carried out in a laboratory flume, where the plants were reproduced assembling plastic strips. In these experiments, the leaf length was larger than the flow depth, reproducing a shallow water situation which is very frequent in lagoons. The results allow one to recognize the hydraulic behaviour of the plants with variation in the Reynolds number of flow and the ratio between the leaf length and the flow depth. Velocity distribution in the section is also examined and a simple flow resistance law is achieved, which expresses Darcy-Weisbach's friction factor as a function only of a particular Reynolds number
Lingua originaleEnglish
pagine (da-a)189-202
RivistaJOURNAL OF HYDRAULIC RESEARCH
Volume44 N. 2
Stato di pubblicazionePublished - 2006

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shallow water
Hydraulics
Reynolds number
Water
hydraulics
Velocity distribution
submerged vegetation
Surface roughness
Friction
Plastics
coastal lagoon
roughness
coastal water
lagoon
friction
plastic
posidonia
Experiments
experiment

All Science Journal Classification (ASJC) codes

  • Civil and Structural Engineering
  • Water Science and Technology

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@article{8b9f9d31674243d59a663a2d5d08edf6,
title = "FLOW RESISTANCE OF POSIDONIA OCEANICA IN SHALLOW WATER",
abstract = "Management of coastal waters and lagoons by mathematical circulation models requires determination of the hydraulic resistance of submerged vegetation. A plant typical of sandy coastal bottoms in the Mediterranean Sea is Posidonia oceanica, which is constituted by very thin and flexible ribbon-like leaves, about 1 cm wide and up to 1.5 m long, and usually covers the bottom with a density of 500-1000 plants/ m2. From the hydraulic viewpoint, P. oceanica constitutes a particular roughness, because, as the velocity increases, the leaves bend more and more until they lie down on the bottom. Although P. oceanica is widespread, in the technical literature it is difficult to find indications about flow resistance due to this plant. In this paper, the results of specific experimental research are reported. The runs were carried out in a laboratory flume, where the plants were reproduced assembling plastic strips. In these experiments, the leaf length was larger than the flow depth, reproducing a shallow water situation which is very frequent in lagoons. The results allow one to recognize the hydraulic behaviour of the plants with variation in the Reynolds number of flow and the ratio between the leaf length and the flow depth. Velocity distribution in the section is also examined and a simple flow resistance law is achieved, which expresses Darcy-Weisbach's friction factor as a function only of a particular Reynolds number",
keywords = "HYDRAULIC RESISTANCE, LAYER, OPEN-CHANNEL FLOW, SMOOTH, TURBULENCE, VEGETATION, VELOCITY DISTRIBUTION",
author = "{La Loggia}, Goffredo and Ferreri, {Giovanni Battista} and Giuseppe Ciraolo",
year = "2006",
language = "English",
volume = "44 N. 2",
pages = "189--202",
journal = "Journal of Hydraulic Research/De Recherches Hydrauliques",
issn = "0022-1686",
publisher = "Taylor and Francis Ltd.",

}

TY - JOUR

T1 - FLOW RESISTANCE OF POSIDONIA OCEANICA IN SHALLOW WATER

AU - La Loggia, Goffredo

AU - Ferreri, Giovanni Battista

AU - Ciraolo, Giuseppe

PY - 2006

Y1 - 2006

N2 - Management of coastal waters and lagoons by mathematical circulation models requires determination of the hydraulic resistance of submerged vegetation. A plant typical of sandy coastal bottoms in the Mediterranean Sea is Posidonia oceanica, which is constituted by very thin and flexible ribbon-like leaves, about 1 cm wide and up to 1.5 m long, and usually covers the bottom with a density of 500-1000 plants/ m2. From the hydraulic viewpoint, P. oceanica constitutes a particular roughness, because, as the velocity increases, the leaves bend more and more until they lie down on the bottom. Although P. oceanica is widespread, in the technical literature it is difficult to find indications about flow resistance due to this plant. In this paper, the results of specific experimental research are reported. The runs were carried out in a laboratory flume, where the plants were reproduced assembling plastic strips. In these experiments, the leaf length was larger than the flow depth, reproducing a shallow water situation which is very frequent in lagoons. The results allow one to recognize the hydraulic behaviour of the plants with variation in the Reynolds number of flow and the ratio between the leaf length and the flow depth. Velocity distribution in the section is also examined and a simple flow resistance law is achieved, which expresses Darcy-Weisbach's friction factor as a function only of a particular Reynolds number

AB - Management of coastal waters and lagoons by mathematical circulation models requires determination of the hydraulic resistance of submerged vegetation. A plant typical of sandy coastal bottoms in the Mediterranean Sea is Posidonia oceanica, which is constituted by very thin and flexible ribbon-like leaves, about 1 cm wide and up to 1.5 m long, and usually covers the bottom with a density of 500-1000 plants/ m2. From the hydraulic viewpoint, P. oceanica constitutes a particular roughness, because, as the velocity increases, the leaves bend more and more until they lie down on the bottom. Although P. oceanica is widespread, in the technical literature it is difficult to find indications about flow resistance due to this plant. In this paper, the results of specific experimental research are reported. The runs were carried out in a laboratory flume, where the plants were reproduced assembling plastic strips. In these experiments, the leaf length was larger than the flow depth, reproducing a shallow water situation which is very frequent in lagoons. The results allow one to recognize the hydraulic behaviour of the plants with variation in the Reynolds number of flow and the ratio between the leaf length and the flow depth. Velocity distribution in the section is also examined and a simple flow resistance law is achieved, which expresses Darcy-Weisbach's friction factor as a function only of a particular Reynolds number

KW - HYDRAULIC RESISTANCE

KW - LAYER

KW - OPEN-CHANNEL FLOW

KW - SMOOTH

KW - TURBULENCE

KW - VEGETATION

KW - VELOCITY DISTRIBUTION

UR - http://hdl.handle.net/10447/16992

M3 - Article

VL - 44 N. 2

SP - 189

EP - 202

JO - Journal of Hydraulic Research/De Recherches Hydrauliques

JF - Journal of Hydraulic Research/De Recherches Hydrauliques

SN - 0022-1686

ER -