Manning’s ‘n’ co-efficient for flexible emergent vegetation in tandem configuration

Noarayanan, L.; Murali, K.; Sundar, V.

doi:10.1016/j.jher.2011.05.002

Cited by 39 publications

(29 citation statements)

References 10 publications

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“…Abrahams et al (1994) found Darcy-Weisbach coefficient better than the Manning's coefficient because it can be applied to different flow states. Noarayanan et al (2012) tested Manning's roughness coefficient under different water flow conditions and plant parameters and concluded that Manning's roughness coefficient is ideal for calculating and describing surface shallow flow resistance. Di Cristo et al (2012) decided that only the Darcy-Weisbach resistance coefficient f can be applied to laminar flow and turbulent flow.…”

Section: Methodsmentioning

confidence: 99%

Simulation study of anisotropic flow resistance of farmland vegetation

Zhang¹,

Yin²,

Zhang³

et al. 2017

Soil & Water Res.

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Farmland vegetation is commonly cultivated with uniform planting spacing and heights. The effect of these features on resistance to hydraulic erosion is unclear. Hydraulic model experiments with the angle between the crop rows and the water flow direction set at 15°, 30°, 45° or 90° were conducted to analyze variation in the law of water flow resistance under partial or complete submergence of the crop. Cultivation can impact the flow resistance on slopes and this effect was greater when the crop was partially submerged. When planting spacing, slope, and water depth were constant, the change of the water flow Darcy-Weisbach resistance coefficient f with crop row-water flow angle was f 15° > f 30° > f 45° > f 90°. This suggests that flow resistance of farmland vegetation is anisotropic. The water flow resistance coefficient of crops that were partly submerged increased with water depth, but decreased with water depth when the crop was completely submerged. At the critical change from partial submergence to complete submergence, the water flow resistance coefficient was the highest when water depth was equal to crop height. These results may be useful for optimizing farmland planting and soil and water conservation.

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Section: Methodsmentioning

confidence: 99%

Simulation study of anisotropic flow resistance of farmland vegetation

Zhang¹,

Yin²,

Zhang³

et al. 2017

Soil & Water Res.

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“…This was similar with the results of Noarayanan et al . (). It was also observed that the combined vegetation layer experiments (1 and 2) imposed more flow resistance than the single vegetation layer experiments.…”

Section: Discussionmentioning

confidence: 97%

“…() and Noarayanan et al . () who investigated and analysed the resistance and roughness coefficient for both SV and EV. This observation suggests that river systems with higher EV density can have a positive influence in maintaining water quality.…”

Section: Discussionmentioning

confidence: 99%

“…The Manning's n due to vegetation was determined using the relationship proposed by Noarayanan et al . (), and this enabled the influence of stem density on flow resistance to be shown clearly;

n_{((), v)} = \{(\frac{1}{v_{((), normalv + normalw)}}) * (R^{2 / 3} * S_{v + w}^{1 / 2})\} - \{(\frac{1}{v_{((), w)}}) * (R^{2 / 3} * S_{((), w)}^{1 / 2})\}

where subscripts v and w refer to vegetation and sidewall, respectively; n (v) is Manning's n due to vegetation; v (v + w) is the average velocity of flow measured in the presence of vegetation; R is hydraulic radius; S v + w is the energy slope with vegetation; v (w) is average velocity measured in the absence of vegetation; and S (w) is the energy slope without vegetation.…”

Section: Methodsmentioning

confidence: 95%

“…To further interpret the experimental results and understand the behaviour of the vegetation in the steady flow, the Manning's n was calculated for the experiments. The Manning's n due to vegetation was determined using the relationship proposed by Noarayanan et al (2011), and this enabled the influence of stem density on flow resistance to be shown clearly;…”

Section: Manning's Roughness Coefficient Nmentioning

confidence: 99%

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An open‐channel flume study of flow characteristics through a combined layer of submerged and emerged flexible vegetation

Anim

Wang

et al. 2013

Ecohydrology

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Flowing water bodies often have plants that differ greatly in size and type, which interfere with fluid flow structure. Although there are studies describing vegetation–flow interactions in ideal laboratory conditions, their practical application is sometimes still difficult. This paper presents results of research involving laboratory simulations channel flow and the effects upon its structure as it passes through a combined layer of submerged and emerged vegetation in an open‐channel flume. Instantaneous time‐average velocity and turbulence at various locations were measured with a 3D acoustic Doppler velocimeter. The experimental results showed that the mean velocity profiles can be divided into three layers: bottom, middle and upper. The velocity profiles show the flow structure was complex variable over time creating mixing velocity layers associated with inflection points and velocity spikes. Turbulence intensity urms, vrms, wrms was nearly invariant for the flow depth at the bottom layer in most locations within the vegetation area. Maximum turbulence intensity occurred within the middle layer and migrated vertically as frontal width of the plant increased. Maximum turbulence intensity fluctuated at the velocity mixing layer where there is significant momentum exchange. The Manning's vegetation roughness coefficient n(v) due to vegetation resistance increased with vegetation density as expected. In all, the results show flow structure varies substantially at the stem section and at the canopy top of submerged vegetation. These analytical findings will be useful in understanding river channel hydraulic transport and mixing processes and useful in river engineering applications and modelling. Copyright © 2013 John Wiley & Sons, Ltd.

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Experimental investigation of 3D flow properties around emergent rigid vegetation

Kumar

Sharma

2022

Ecohydrology

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The condition of emergent or submerged vegetation plays a vital role in affecting the flow behaviour in open channels. To understand the flow processes in free surface flows under emergent rigid vegetation condition, an extensive experimental investigation is performed in a laboratory channel with staggered combination of emergent rigid vegetation. Three-dimensional velocities data are collected by ADV at various section and position of vegetated channel. The three-dimensional flow properties such as velocity distribution, turbulence intensity, turbulent kinetic energy, Reynolds shear stress in vegetation, and non-disturbed region are analysed and compared with the longitudinal and transverse length of vegetated zone. In the vegetation region, the longitudinal velocity in free stream region decreases as compared with nondisturbed region. However, the vertical velocity also decreases in free stream region except at the centre line of channel cross-section. Variations in velocity in the vegetation section were observed because of the local effect induced by the vegetation stems. Three-dimensional Reynolds shear stress and turbulent intensity were weaker in magnitude at vegetation region. The presence of vegetation reduces the longitudinal profile of flow velocity, Reynolds shear stress and turbulence intensities, which means that vegetation can be used as an effective tool to reduce the flow resistance.The turbulent kinetic energy, skewness and kurtosis are also evaluated and compared between the vegetated and non-vegetated zone. The outcomes of the results provide an important view to understand flow behaviour at immediately front and immediately behind of vegetation stem.

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Manning’s ‘n’ co-efficient for flexible emergent vegetation in tandem configuration

Cited by 39 publications

References 10 publications

Simulation study of anisotropic flow resistance of farmland vegetation

Simulation study of anisotropic flow resistance of farmland vegetation

An open‐channel flume study of flow characteristics through a combined layer of submerged and emerged flexible vegetation

Experimental investigation of 3D flow properties around emergent rigid vegetation

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