Relatively Rough Flow Resistance Equations

Smart, Graeme; Duncan, Maurice J.; Walsh, Jeremy M.

doi:10.1061/(asce)0733-9429(2002)128:6(568)

Cited by 154 publications

(137 citation statements)

References 13 publications

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“…However, for extreme cases such as rivers where there is large scale bed roughness due to coarser bed material, conventional 1/6th power law does not agree with log law and larger exponent is required. And according to Smart et al [16], the power law exponent can increase to 1/2 in high relative roughness conditions. And so he recommends 1/4th power for the range below is more sensitive to bed material size over rough bed rather than over smooth bed.…”

Section: N R Dmentioning

confidence: 93%

“…There are a number of studies that differentiate power law exponent of the flow over rough bed with that over smooth bed. Although many articles indicate that 1/6 is generally accepted as a power law exponent, on the other side, some articles indicate that there may be significant change in the power law exponent for the flow over rough bed [4,8,16]. According to Chen [4], power law exponent varies with Reynolds number and relative roughness.…”

Section: N R Dmentioning

confidence: 99%

See 1 more Smart Citation

Power Law Exponents for Vertical Velocity Distributions in Natural Rivers

Lee¹,

Lee²,

Kim³

et al. 2013

ENG

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While log law is an equation theoretically derived for near-bed region, in most cases, power law has been researched by experimental methods. Thus, many consider it as an empirical equation and fixed power law exponents such as 1/6 and 1/7 are generally applied. However, exponent of power law is an index representing bed resistance related with relative roughness and furthermore influences the shapes of vertical velocity distribution. The purpose of this study is to investigate characteristics of vertical velocity distribution of the natural rivers by testing and optimizing previous methods used for determination of power law exponent with vertical velocity distribution data collected with ADCPs during the years of 2005 to 2009 from rivers in South Korea. Roughness coefficient has been calculated from the equation of Limerinos. And using theoretical and empirical formulae, and representing relationships between bed resistance and power law exponent, it has been evaluated whether the exponents suggested by these equations appropriately reproduce vertical velocity distribution of actual rivers. As a result, it has been confirmed that there is an increasing trend of power law exponent as bed resistance increases. Therefore, in order to correctly predict vertical velocity distribution in the natural rivers, it is necessary to use an exponent that reflects flow conditions at the field.

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Section: N R Dmentioning

confidence: 93%

Section: N R Dmentioning

confidence: 99%

Power Law Exponents for Vertical Velocity Distributions in Natural Rivers

Lee¹,

Lee²,

Kim³

et al. 2013

ENG

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“…As consequence, in a coastal sector it is possible to obtain an evaluation of the present roughness useful in the elaboration of a near-future scenario, but that is not representative of a past tsunami impact. According to several studies performed on open channel flows (Smart et al, 2002;Smart, 2004) the roughness characteristics of the channel bottom are very well correlated with the standard deviation of the bottom surface, so it is possible to use in situ Terrestrial Laser Scanner (TLS) data to calculate Manning's n for given flow conditions. …”

Section: Hydrodynamic Equationsmentioning

confidence: 99%

Determination of Tsunami Inundation Model Using Terrestrial Laser Scanner Techniques

Mastronuzzi¹,

Pignatelli²

2011

The Tsunami Threat - Research and Technology

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“…Vegetation is thus a key factor in the interrelated systems of flow, sediment transport and geomorphology in rivers [4]. While the hydraulic resistance of solid boundaries with small-scale irregularities is quite well understood, situations in which resistance elements are of similar size to the flow depths still pose large problems [5]. The effects of vegetation on flow are significant and cause difficulties in hydraulic design.…”

Section: Introductionmentioning

confidence: 99%

Multilayer Numerical Modeling of Flows through Vegetation Using a Mixing-Length Turbulence Model

Barrios-Piña¹,

Ramírez-León

Rodríguez-Cuevas

et al. 2014

Water

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This work focuses on the effects of vegetation on a fluid flow pattern. In this numerical research, we verify the applicability of a simpler turbulence model than the commonly used k-ε model to predict the mean flow through vegetation. The novel characteristic of this turbulence model is that the horizontal mixing-length is explicitly calculated and coupled with a multi-layer approach for the vertical mixing-length, within a general three-dimensional eddy-viscosity formulation. This mixing-length turbulence model has been validated in previous works for different kinds of non-vegetated flows. The hydrodynamic numerical model used for simulations is based on the Reynolds-averaged Navier-Stokes equations for shallow water flows, where a vegetation shear stress term is considered to reproduce the effects of drag forces on flow. A second-order approximation is used for spatial discretization and a semi-implicit Lagrangian-Eulerian scheme is used for time discretization. In order to validate the numerical results, we compare them against experimental data reported in the literature. The comparisons are carried out for two cases of study: submerged vegetation and submerged and emergent vegetation, both within an open channel flow.

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Relatively Rough Flow Resistance Equations

Cited by 154 publications

References 13 publications

Power Law Exponents for Vertical Velocity Distributions in Natural Rivers

Power Law Exponents for Vertical Velocity Distributions in Natural Rivers

Determination of Tsunami Inundation Model Using Terrestrial Laser Scanner Techniques

Multilayer Numerical Modeling of Flows through Vegetation Using a Mixing-Length Turbulence Model

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