Incipient Motion of Sediment Particles Over Fixed Beds

Novák, Pavel; Nalluri, C.

doi:10.1080/00221688409499405

Cited by 78 publications

(63 citation statements)

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“…The author presented an equation in two forms. The first equation is the same as the equations presented earlier (by Ab Ghani et al, 1999;El-Zaemey, 1991;Novak and Nalluri, 1984) in the form of ( )…”

Section: Overview Of Exiting Equationsmentioning

confidence: 78%

“…The maximum diameter of sediment particles employed was greater than Novak and Nalluri's (1984). El-Zaemey (1991) presented the following equation, which has the same form as Novak and Nalluri's (1984) equation but different coefficients:…”

Section: Overview Of Exiting Equationsmentioning

confidence: 99%

“…This method does not refer to sediment and flow characteristics and is thus not reliable, as it leads to under or overestimated critical velocity for incipient motion . Therefore, several experimental research works have been conducted with a large variety of equations to estimate the incipient motion velocity (Ab Ghani et al, 1999;El-Zaemey, 1991;Novak and Nalluri, 1984;Safari et al, 2011). Some equations are applied extensively in many designs owing to their simplicity, but these equations do not consider the thickness of sediment deposited on the bed, which has significant impact on the dimensionless shear stress in the Shields diagram (Bong et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

“…The median diameters of sediment particles ranged from 3.6 mm to 37.2 mm. Novak and Nalluri (1984) considered Fr as a function of d/R and presented the following equation:…”

Section: Introductionmentioning

confidence: 99%

“…The results of the MLP neural network and several regression-based equations are compared with the MLP-DT results. Novak and Nalluri (1984) conducted different experimental tests on the incipient motion of sediment particles in flumes with rough and smooth beds. The flumes were rectangular glass-walled, 15 m and 6 m long and 300 mm wide.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Design of a new hybrid artificial neural network method based on decision trees for calculating the Froude number in rigid rectangular channels

Ebtehaj

Bonakdari

Zaji

et al. 2016

Journal of Hydrology and Hydromechanics

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A vital topic regarding the optimum and economical design of rigid boundary open channels such as sewers and drainage systems is determining the movement of sediment particles. In this study, the incipient motion of sediment is estimated using three datasets from literature, including a wide range of hydraulic parameters. Because existing equations do not consider the effect of sediment bed thickness on incipient motion estimation, this parameter is applied in this study along with the multilayer perceptron (MLP), a hybrid method based on decision trees (DT) (MLP-DT), to estimate incipient motion. According to a comparison with the observed experimental outcome, the proposed method performs well (MARE = 0.048, RMSE = 0.134, SI = 0.06, BIAS = -0.036). The performance of MLP and MLP-DT is compared with that of existing regression-based equations, and significantly higher performance over existing models is observed. Finally, an explicit expression for practical engineering is also provided.

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Section: Overview Of Exiting Equationsmentioning

confidence: 78%

Section: Overview Of Exiting Equationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…The median diameters of sediment particles ranged from 3.6 mm to 37.2 mm. Novak and Nalluri (1984) considered Fr as a function of d/R and presented the following equation:…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Design of a new hybrid artificial neural network method based on decision trees for calculating the Froude number in rigid rectangular channels

Ebtehaj

Bonakdari

Zaji

et al. 2016

Journal of Hydrology and Hydromechanics

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Direct measurements of lift and drag on shallowly submerged cobbles in steep streams: Implications for flow resistance and sediment transport

Lamb

Brun

Fuller

2017

Water Resources Research

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Steep mountain streams have higher resistance to flow and lower sediment transport rates than expected by comparison with low gradient rivers, and often these differences are attributed to reduced near‐bed flow velocities and stresses associated with form drag on channel forms and immobile boulders. However, few studies have directly measured drag and lift forces acting on bed sediment for shallow flows over coarse sediment, which ultimately control sediment transport rates and grain‐scale flow resistance. Here we report on particle lift and drag force measurements in flume experiments using a planar, fixed cobble bed over a wide range of channel slopes (0.004 < S < 0.3) and water discharges. Drag coefficients are similar to previous findings for submerged particles (CD ∼ 0.7) but increase significantly for partially submerged particles. In contrast, lift coefficients decrease from near unity to zero as the flow shallows and are strongly negative for partially submerged particles, indicating a downward force that pulls particles toward the bed. Fluctuating forces in lift and drag decrease with increasing relative roughness, and they scale with the depth‐averaged velocity squared rather than the bed shear stress. We find that, even in the absence of complex bed topography, shallow flows over coarse sediment are characterized by high flow resistance because of grain drag within a roughness layer that occupies a significant fraction of the total flow depth, and by heightened critical Shields numbers and reduced sediment fluxes because of reduced lift forces and reduced turbulent fluctuations.

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Bedload transport in two gravel‐bedded streams

Carling

1989

Earth Surf Processes Landf

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Bedload transport measurements in two upland streams are considered as a function of the excess stream power exerted on the bed by the flow.During low flows when the framework gravels remain undisturbed, fine sediments are winnowed from the bed-surface layer once a threshold of 3.4 W m-' is exceeded and the transport rate is strongly supply limited. However for stream powers in excess of 15 W m--2 framework gravels are mobilized and the efficiency of the transport process approaches a local maximum of about 1 per cent for discharges up to 2/3 of bankfull.An inverse depth dependence in the efficiency of the transport process was noted but although bedload calibre increased as a function of discharge its influence on efficiency could not be demonstrated. However it was suspected that the size-sorting relationships of the bed-material in a number of rivers in relation to the transport efficiency might profitably be examined further.

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Incipient Motion of Sediment Particles Over Fixed Beds

Cited by 78 publications

References 1 publication

Design of a new hybrid artificial neural network method based on decision trees for calculating the Froude number in rigid rectangular channels

Design of a new hybrid artificial neural network method based on decision trees for calculating the Froude number in rigid rectangular channels

Direct measurements of lift and drag on shallowly submerged cobbles in steep streams: Implications for flow resistance and sediment transport

Bedload transport in two gravel‐bedded streams

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