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Abstract(s)
A vegetação ripícola desempenha importantes funções no equilíbrio do ecossistema, bem
como melhora a qualidade da água. Nas últimas décadas, devido às preocupações
ambientais e à proteção contra inundações, a necessidade de entender o comportamento
hidrodinâmico dos rios tem crescido. A presença de vegetação afeta a resistência
hidráulica, o transporte de massas, a quantidade de movimento e a estrutura do
escoamento turbulento, com várias implicações ecológicas e morfológicas.
O objetivo da presente dissertação é compreender a hidrodinâmica do escoamento na
interface de áreas com vegetação.
De modo a interpretar melhor a influencia da vegetação na estrutura do escoamento foram
realizados ensaios experimentais no Laboratório de Hidráulica Fluvial e das Estruturas
(LHFE), na Universidade da Beira Interior (UBI). O leito do canal foi parcialmente
coberto por uma matriz uniforme de cilindros metálicos alinhados.
O trabalho prático consistiu na medição de campos de velocidade instantânea com o
auxílio de um Velocímetro Doppler Acústico (ADV), e o tratamento de dados foi realizado
num software próprio, denominado WinADV.
Os resultados obtidos permitiram concluir que a distribuição das velocidades longitudinais
apresentam perfis típicos, quer para o corredor ripícola, quer para o canal principal, sendo
quase constante no canal com hastes, e quase logarítmico a aumentar para a superfície no
canal principal.
A existência de um corredor ripícola leva a que parte do escoamento se afaste dele,
percorrendo o trajeto que oferece menor resistência, havendo transferências de massas
entre a zona vegetada e o canal principal. Foi ainda possível concluir que o efeito local da
presença das hastes é suprimido pelo efeito de corte da camada de mistura.
The riparian vegetation has an important role not only in the balance of the ecosystems but also on water quality improvement. In the past decades, due to environmental concerns and protection against floods, the need to understand the hydrodynamical behavior of the rivers has been growing. The existence of vegetation affects the hydraulic resistance, on mass transport, quantity of movement and turbulent flow structure, which leads to several environmental and morphological implications. The aim of this thesis is to understand the hydrodynamics of the flow in the interface of vegetated areas. In order to better understand the influence of vegetation in the flow structure, several experimental studies were carried out at the Laboratory of Hydraulics and Structures (LHFE), at University of Beira Interior (UBI). During these studies, the channel bed was partially covered by an array of circular in a staggered arrangement. In order to meet the proposed objective, the experimental tests were done by measurement instantaneous velocity fields using an ADV device and the data treatment was done with a specific software known as WinADV. The results reveal that the distribution of longitudinal velocities show typical profiles in both vegetated and non-vegetated area. It was also observed that for vegetated areas the profile presented a constant behavior while the main channel exhibited a logarithmic profile. The existence of a riparian zone leads to that part of the flow move away from it and consequently, follow the path that offers less resistance. In this way, there are mass transfer between vegetated and non-vegetated area. It was also concluded that the shear stress effect of the mixing layer overlaps the local effect of the presence of the stem.
The riparian vegetation has an important role not only in the balance of the ecosystems but also on water quality improvement. In the past decades, due to environmental concerns and protection against floods, the need to understand the hydrodynamical behavior of the rivers has been growing. The existence of vegetation affects the hydraulic resistance, on mass transport, quantity of movement and turbulent flow structure, which leads to several environmental and morphological implications. The aim of this thesis is to understand the hydrodynamics of the flow in the interface of vegetated areas. In order to better understand the influence of vegetation in the flow structure, several experimental studies were carried out at the Laboratory of Hydraulics and Structures (LHFE), at University of Beira Interior (UBI). During these studies, the channel bed was partially covered by an array of circular in a staggered arrangement. In order to meet the proposed objective, the experimental tests were done by measurement instantaneous velocity fields using an ADV device and the data treatment was done with a specific software known as WinADV. The results reveal that the distribution of longitudinal velocities show typical profiles in both vegetated and non-vegetated area. It was also observed that for vegetated areas the profile presented a constant behavior while the main channel exhibited a logarithmic profile. The existence of a riparian zone leads to that part of the flow move away from it and consequently, follow the path that offers less resistance. In this way, there are mass transfer between vegetated and non-vegetated area. It was also concluded that the shear stress effect of the mixing layer overlaps the local effect of the presence of the stem.
Description
Keywords
Adv Anisotropia Escoamento Turbulento Interface Vegetação Emersa Rígida