Investigation of turbulence characteristics in channel with dense vegetation

Afzalimehr, Hossein; Moghbel, Razieh; Gallichand, Jacques; Sui, Jueyi

doi:10.1016/s1001-6279(11)60093-0

Cited by 40 publications

(25 citation statements)

References 39 publications

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“…Mazumder et al (2009) have chosen H = 0, 2, 5, 6, 10, 15 in quadrant analysis over bedforms. Afzalimehr et al (2011) considered H = 0, 1, 2, 3 to investigate the characteristics of turbulent flow in channel with dense vegetation. A wide range of hole sizes, H = 0, 1, 2…10, 15, 20 are considered in order to recognize the differences between the weak and strong events in bursting process.…”

Section: Frequency Of Eventmentioning

confidence: 99%

“…Although quadrant analysis is traditionally performed for conditional sampling of the Reynolds shear stress and turbulent heat flux, recent studies (e.g., Poggi et al 2004;Ghisalberti and Nepf 2006;Zhu et al 2007;Afzalimehr et al 2011) extended the technique to include more general properties of turbulence in plant canopy flows, such as turbulent kinetic energy, vorticity, and dissipation rate. Jafari and Keshavarzi (2010) investigated turbulence flow and sediment entrainment over the ripples by using quadrant analysis.…”

Section: Introductionmentioning

confidence: 99%

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Investigation of turbulence flow and sediment entrainment around a bridge pier

Izadinia

Heidarpour

Schleiss

2012

Stoch Environ Res Risk Assess

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Local scour around the obstacles such as bridge pier is the result of complex interaction between turbulent flow and sediment particles at the mobile bed. The entrainment of sediment particles from the bed is stochastic in nature and it is strongly influenced by instantaneous shear stresses of the bursting process. The focus of this study is the investigation of turbulent flow and analysis of contribution of each bursting events to the Reynolds shear stress to find the dominant bursting events and also the flow structure around the circular bridge pier. The velocities around the bridge pier were measured in three dimensions using an Acoustic Doppler Velocimeter. These velocities were measured at different positions around the bridge pier and at different depths. Quadrant analysis is used to recognize the susceptible regions for sediment entrainment and deposition. According to quadrant analysis sedimentation is the dominant effect in the scour hole whereas at higher levels the erosion force becomes more important. In downstream of the pier, sediment particles are put in suspension and transported downstream due to sweep. Our results indicate that the secondary currents are more dominant in downstream of the pier, as compared to the upstream of the pier. Consequently the maximum velocity in downstream of the pier takes place in a location closer to the bed. In upstream of the pier the streamwise component of velocity becomes positive for which the universal log-law turns out to be valid.

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Section: Frequency Of Eventmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Investigation of turbulence flow and sediment entrainment around a bridge pier

Izadinia

Heidarpour

Schleiss

2012

Stoch Environ Res Risk Assess

View full text Add to dashboard Cite

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“…The quadrant analysis has been applied to canopy turbulent flows, e.g. wheat and bushes, over rigid and flexible canopies (Afzalimehr et al, 2011;Ghisalberti and Nepf, 2006) over intensive grass.…”

Section: Conditional Statistics Of Reynolds Shear Stressmentioning

confidence: 99%

“…In this study, the value of hole size is determined based on satisfaction of the equation (2). The range of H used in from 0 to 8 for our analysis as considered in other studies (Afzalimehr et al, 2011).…”

Section: Conditional Statistics Of Reynolds Shear Stressmentioning

confidence: 99%

“…Literature review in FPG flow reveals that the distributions of velocity, Reynolds shear stress and turbulence intensities under condition of steady flow have been investigated over smooth bed (Kachwal et al, 2012); over two dimensional bed forms (Mazumdar et al, 2009); over gravel-bed channels (Afzalimehr and Rennie, 2009;Afzalimehr et al, 2010;Song and Chiew, 2001); over sand bed with sediment transport conditions (Emadzadeh et al, 2010;Jamieson et al, 2013;Liu et al, 2012;Rennie et al, 2002); over cobble bed (Afzalimehr, 2010); and over vegetated bed (Afzalimehr et al, 2011;Ghisalberti and Nepf, 2006;Järvelä, 2005;Luhar et al, 2008). Yue et al (2007) conducted a case study in a flume that the channel bed covered by canopy.…”

Section: Introductionmentioning

confidence: 99%

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Turbulence characteristics of favorable pressure gradient flows in gravel-bed channel with vegetated walls

Najafabadi

Afzalimehr

Sui

2015

Journal of Hydrology and Hydromechanics

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Abstract:Field observations showed that in many gravel-bed rivers, rice stems and gravel interact with each other and affect the flow structure. This calls to conduct research in more details in laboratory to better understand impacts of interaction between rice stems and gravel bed rivers on the flow structure. The outcome of such investigations can improve the estimation of drag coefficient in hydrodynamic models. Experiments were carried out in a flume with gravel bed and the vegetated vertical flume walls to investigate turbulence characteristics under favorable pressure gradient flows. Results showed that the stress fraction involves both the sweep and ejection dominance near the vegetated flume walls, showing no negative Reynolds shear stress near water surface. The values of exuberance ratio play a significant role on the magnitude of the Reynolds shear stress which varies with the distance from the vegetation. Quadrant analysis reveals that a major part of the momentum flux is transported during a short period of strong turbulence activity near the bed at the central axis. Augmentation of the hole size makes difference between contributions of sweep and ejection with those of the outward and inward interactions near the bed, however, the hole size doesn't play any role near the water surface.

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Turbulent flow structures and geomorphic characteristics of a mining affected alluvial channel

Barman

Kumar

Sarma

2018

Earth Surf Processes Landf

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Sediment mining in rivers may have a major impact on river geomorphology and research is required to quantify these impacts. In this research, experimental studies were conducted to analyse the morphological changes of channel bed and the turbulent characteristics of flow in the presence of mining. The channel bed profile shows erosion at the bank of the pit and that the erosion expands to the whole width of the channel and propagates downstream with time. The deposition of sediment occurs along the upstream edge of the pit and the depth of the pit decreases with time. Velocity reversal occurs at the central bottom of the pit related to a recirculation zone. Reynolds shear stress and the turbulent intensities become higher in the mining pit region and downstream of it as compared to the upstream section, causing a more rapid movement of bed particles. Analysis of the bursting phenomenon shows that the contribution of sweep and ejection events to the total Reynolds shear stress is more dominant over outward and inward interaction events. The dominance of the sweep event over ejection is observed at the near‐bed region for all the sections, but the depth range of dominance of sweep events in the pit and downstream of the pit is found to be more than the upstream. The increase in thickness is responsible for the increase in bed material transport. The increased sediment transport capacity at the mining pit and downstream of it caused the deformation and lowering of channel bed downstream. An empirical formulation of bedload transport for mining induced channels is derived from two different sized uniform bed materials. Copyright © 2018 John Wiley & Sons, Ltd.

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Investigation of turbulence characteristics in channel with dense vegetation

Cited by 40 publications

References 39 publications

Investigation of turbulence flow and sediment entrainment around a bridge pier

Investigation of turbulence flow and sediment entrainment around a bridge pier

Turbulence characteristics of favorable pressure gradient flows in gravel-bed channel with vegetated walls

Turbulent flow structures and geomorphic characteristics of a mining affected alluvial channel

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