Turburence structure and coherent motion in vegetated canopy open-channel flows

Nezu, Iehisa; Sanjou, Michio

doi:10.1016/j.jher.2008.05.003

Cited by 220 publications

(252 citation statements)

References 41 publications

Supporting

Mentioning

218

Contrasting

Unclassified

Order By: Relevance

“…Figure 8 shows the different possible configurations for each of the three length scales: s, k and D. To determine experimentally l 0 , the flow rate by integrating the calculated vertical velocity profile (steps 3c, 3d and 3e) is compared to the measured flow rate with an optimization method (simplex algorithm from Matlab). For all experiments from literature (Kouwen and Unny, 1969;Meijer and Velzen, 1999;Lopez and Garcia, 2001;Righetti and Armanini, 2002;Poggi et al, 2004;Jarvela, 2005;Ghisalberti and Nepf, 2006;Murphy and Nepf, 2007;Kubrak et al, 2008;Nezu and Sanjou, 2008;Huai et al, 2009;Yang and Choi, 2009;Florens et al, 2013) (2008) are reused, together with those obtained specifically for the present study. As indicated by Konings et al (2012), the experiments carried out with leafy vegetation behaved in a particular way because of viscosity terms.…”

Section: Submerged Conditionsmentioning

confidence: 99%

“…For the experiments performed in this study, the averaged error is 15.8%. Poggi et al (2004), Meijer and Velzen (1999), Ghisalberti and Nepf (2006), Murphy and Nepf (2007), Nezu and Sanjou (2008), Yang and Choi (2009), Kubrak et al (2008), Jarvela (2005, Kouwen and Unny (1969), Florens et al (2013), Huai et al (2009), Righetti andArmanini (2002).…”

Section: Submerged Conditionsmentioning

confidence: 99%

See 1 more Smart Citation

Design of emergent and submerged rock-ramp fish passes

Cassan

Laurens

2016

Knowl. Manag. Aquat. Ecosyst.

View full text Add to dashboard Cite

-An analytical model is developed to calculate the stage-discharge relationship for emergent and submerged rock-ramp fish passes. A previous model has been modified and simplified to be adapted to a larger range of block arrangement. For submerged flows, a two-layer model developed for aquatic canopies is used. A turbulent length scale is proposed to close the turbulence model thanks to a large quantity of data for fully rough flows from the literature and experiments. This length scale depends only on the characteristic lengths of arrangements of obstacles. Then the coefficients of the logarithmic law above the canopy can also be deduced from the model. As a consequence, the total discharge through the fish pass is computed by integrating the vertical velocity profiles. A good fit is found between the model and commonly observed values for fish pass or a vegetated canopy. The discharge of the fish pass is then accurately estimated for a large range of hydraulic conditions, which could be useful for estimating fish passability through the structure.

show abstract

Section: Submerged Conditionsmentioning

confidence: 99%

Section: Submerged Conditionsmentioning

confidence: 99%

Design of emergent and submerged rock-ramp fish passes

Cassan

Laurens

2016

Knowl. Manag. Aquat. Ecosyst.

View full text Add to dashboard Cite

show abstract

“…The vegetation density a (stems/m) was determined by dividing the projected plant area perpendicular to the flow by the vegetation volume (Nezu and Sanjou, 2008) according to a ¼ ðA=V Þ ¼ ðnA i =WhLÞ where n is the number of plants in area W Â L (W is the channel width and L is the channel length), A i is the mean frontal vegetal area and h is the vegetation bending height. To express the vegetation density as a dimensionless factor, the vegetation density was calculated as λ = a Â h and, in this study, the dimensionless vegetation density was 0·243.…”

Section: Laboratory Experiments and Field Measurementsmentioning

confidence: 99%

Non-uniform flow over cobble bed with submerged vegetation strip

Afzalimehr

Barahimi

Sui

2019

Proceedings of the Institution of Civil Engineers - Water Manag

View full text Add to dashboard Cite

2 3To better understand the influence of non-uniform flow in coarse-bed streams with a submerged vegetation strip on flow characteristics, data were collected from experiments in a laboratory flume and field investigations in a cobblebed river reach in central Iran. The results of the experiments and field observations showed that the velocity profiles for non-uniform flows in cobble-bed streams with vegetation strips can be divided into either two or three sub-zones. The velocity profiles of non-uniform flows in the laboratory flume and cobble-bed stream deviated from the log law in the wake and mixing zones, but fitted approximately in the log-law layer zone. The distribution of Reynolds stress for non-uniform flows was influenced by the vegetation strip and showed a non-concave shape. Near the channel bed, sweep motion occurred more frequently than the ejection process. Close to the top of vegetation strip, the correlation coefficient (r u 0 w 0 ) was negative, indicating downward momentum transport due to sweep and ejection processes. However, r u 0 w 0 was positive near the water surface, indicating upward momentum by the vegetation strip due to inward and outward interactions. The study shows that laboratory results cannot be easily applied to natural rivers without considerable assumptions.

show abstract

“…Many previous studies have incorporated rigid elements to simulate vegetation fields in directional fluid flow (Nepf 1999;Poggi et al 2004;Nezu and Sanjou 2008), directional atmospheric flow (Finnigan 2000), and in wave fluid flow (Dalrymple et al 1984), but there have been fewer studies that have incorporated flexible elements into the experimental design in either direct flow (Ghisalberti and Nepf 2006;Wunder et al 2009) or in wave conditions (Augustin et al 2009). Some research has looked at simpler properties such as wet biomass (Penning et al 2009) for defining the parameters of vegetation, but a more efficient characterization method is still needed.…”

Section: Introductionmentioning

confidence: 99%

“…Studies focusing on the characterization of turbulence through laser and Doppler techniques (Finnigan 2000;Poggi et al 2004;Nezu and Sanjou 2008) have provided insight into the wake effects and eddy structures that develop in canopies. While this is fundamental to deeper understanding of the interactions within the canopy, there is also a need for breaking the complexities down into simpler components such as the basic characterization of drag force differences occurring due to the flexibility of vegetation.…”

Section: Introductionmentioning

confidence: 99%

Flume instrumentation for measurement of drag on flexible elements under waves

2014

View full text Add to dashboard Cite

Understanding energy dissipation by vegetation is critical for the effective management of shoreline erosion. Current methods for estimating energy dissipation require plant-specific parameters that are difficult to estimate for the large variety of plant morphologies used in shoreline protection, requiring testing on each species of interest. A simple and fast method to characterize drag in terms of wave interaction and obstruction natural frequency is needed to fully explore drag forces on vegetation. Our method directly measures hydrodynamic forces on individual plant shoots using a torque sensor mounted beneath the bed of a flume. This sensor allows data to be collected simply and inexpensively with high temporal accuracy that provides insight into drag forces and torque frequency from a variety of flexible elements when coupled with wave monitoring. The technique can evaluate several types of obstructions quickly without the need to set up an entire obstruction field. The data collected also suggest that more flexible objects result in less drag force on each element and suggest that frequency response is related to the frequencies existing in the driving wave and the natural frequency of the obstruction element, although harmonic synchronization appears to occur in some cases doubling the expected drag force magnitude.

show abstract

Turburence structure and coherent motion in vegetated canopy open-channel flows

Cited by 220 publications

References 41 publications

Design of emergent and submerged rock-ramp fish passes

Design of emergent and submerged rock-ramp fish passes

Non-uniform flow over cobble bed with submerged vegetation strip

Flume instrumentation for measurement of drag on flexible elements under waves

Contact Info

Product

Resources

About