Characteristics of flow through rigid, emergent and sparse vegetation

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Abstract

This paper looks into the flow profiles in terms of longitudinal and transverse velocities, turbulence intensity and turbulent kinetic energy in relation to the vegetation density, flow depth and stem Reynolds number. An experimental study was conducted in a fully vegetated flume, whereby a control volume was selected for detailed velocity measurement using Acoustic Doppler Velocimeter (ADV). This research considered 0.97%, 3.90% and 7.80% vegetation density or solid volume fractions (SVF) which are categorised as sparse in the lab work. Series of experiments were conducted in uniform flow condition with stem Reynolds number, Red ranging between 1300 and 3000. Experimental results managed to capture the wake area (velocity deficit; ūxz/U < 1) and fast flow region (velocity enhance; ūxz/U > 1). The boundary between the wake area and fast flow region is reflected by the highest magnitude of the normalised longitudinal turbulence intensity and turbulent kinetic energy. Positive normalised transverse velocity represents the flow diversion away from the vegetation and the negative normalised transverse velocity indicates flux towards the centre of the wake. Both turbulence intensity and turbulent kinetic energy display no observable relation with the flow depth. This is probably because the characteristic length for turbulent flow through vegetation is the stem diameter.

Original languageEnglish
Pages (from-to)77-85
Number of pages9
JournalJurnal Teknologi
Volume78
Issue number10
DOIs
Publication statusPublished - 1 Oct 2016

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Kinetic energy
Turbulence
Acoustic wave velocity measurement
Reynolds number
Velocimeters
Turbulent flow
Volume fraction
Fluxes
Experiments

Keywords

  • Emergent vegetation
  • Mean velocity
  • Transverse velocity
  • Turbulence intensity
  • Turbulent kinetic energy

ASJC Scopus subject areas

  • Engineering(all)

Cite this

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title = "Characteristics of flow through rigid, emergent and sparse vegetation",
abstract = "This paper looks into the flow profiles in terms of longitudinal and transverse velocities, turbulence intensity and turbulent kinetic energy in relation to the vegetation density, flow depth and stem Reynolds number. An experimental study was conducted in a fully vegetated flume, whereby a control volume was selected for detailed velocity measurement using Acoustic Doppler Velocimeter (ADV). This research considered 0.97{\%}, 3.90{\%} and 7.80{\%} vegetation density or solid volume fractions (SVF) which are categorised as sparse in the lab work. Series of experiments were conducted in uniform flow condition with stem Reynolds number, Red ranging between 1300 and 3000. Experimental results managed to capture the wake area (velocity deficit; ūxz/U < 1) and fast flow region (velocity enhance; ūxz/U > 1). The boundary between the wake area and fast flow region is reflected by the highest magnitude of the normalised longitudinal turbulence intensity and turbulent kinetic energy. Positive normalised transverse velocity represents the flow diversion away from the vegetation and the negative normalised transverse velocity indicates flux towards the centre of the wake. Both turbulence intensity and turbulent kinetic energy display no observable relation with the flow depth. This is probably because the characteristic length for turbulent flow through vegetation is the stem diameter.",
keywords = "Emergent vegetation, Mean velocity, Transverse velocity, Turbulence intensity, Turbulent kinetic energy",
author = "Suraya Sharil and {Wan Mohtar}, {Wan Hanna Melini} and {Mohd Razali}, {Siti Fatin}",
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AB - This paper looks into the flow profiles in terms of longitudinal and transverse velocities, turbulence intensity and turbulent kinetic energy in relation to the vegetation density, flow depth and stem Reynolds number. An experimental study was conducted in a fully vegetated flume, whereby a control volume was selected for detailed velocity measurement using Acoustic Doppler Velocimeter (ADV). This research considered 0.97%, 3.90% and 7.80% vegetation density or solid volume fractions (SVF) which are categorised as sparse in the lab work. Series of experiments were conducted in uniform flow condition with stem Reynolds number, Red ranging between 1300 and 3000. Experimental results managed to capture the wake area (velocity deficit; ūxz/U < 1) and fast flow region (velocity enhance; ūxz/U > 1). The boundary between the wake area and fast flow region is reflected by the highest magnitude of the normalised longitudinal turbulence intensity and turbulent kinetic energy. Positive normalised transverse velocity represents the flow diversion away from the vegetation and the negative normalised transverse velocity indicates flux towards the centre of the wake. Both turbulence intensity and turbulent kinetic energy display no observable relation with the flow depth. This is probably because the characteristic length for turbulent flow through vegetation is the stem diameter.

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