Effect of Bed-Load Movement on Flow Friction Factor

Song, Tiancheng; Chiew, Yee‐Meng; Chin, C. O.

doi:10.1061/(asce)0733-9429(1998)124:2(165)

Cited by 69 publications

(61 citation statements)

References 13 publications

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“…The results of the¯ume experiment conducted for this study corroborate those of Song et al (1998) showing that increasing the concentration of bedload causes an augmentation of the eect of bedload on¯ow Figure 2. Normalised velocity dierence graphs for the sediment concentrations analysed in this study.…”

Section: Discussionsupporting

confidence: 86%

“…While Wiberg and Rubin (1989) pointed out that the eect of sediment concentration could potentially be important in situations where the river system is starved or oversupplied with sediment, they also noted that the dependence of roughness on concentration could not be included in a simple manner in their analysis. To the best of our knowledge, Song et al (1998) provided the only attempt to study speci®cally the eect of sediment concentration on bedload roughness. In their¯ume experiments, they observed that bedload transport caused an increase of the Darcy-Weisbach friction factor f and that the magnitude of this increase was positively related to sediment concentration.…”

Section: Introductionmentioning

confidence: 99%

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The effect of sediment concentration on bedload roughness

Bergeron

Carbonneau

1999

Hydrol. Process.

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Abstract:Bedload roughness is the roughness produced by sediment transported near the bed. While it is well established that the magnitude of this roughness is proportional to the thickness of the moving sediment layer, the eect of sediment concentration remains largely unknown. This paper presents the results of a¯ume experiment that was designed to investigate the eect of sediment concentration on bedload roughness. The experiment consisted of creating¯ow conditions where bedload transport is supply-limited and injecting gravel size particles (D 50 7.4 mm) at the upstream end of the¯ume in order to produce bedload transport. While keeping¯ow conditions constant, sediment concentration was varied by successively increasing the injection rate of gravel in the¯ow. For each injection rate,¯ow velocity pro®les were measured in order to evaluate changes of mean¯ow velocity U, shear velocity u * , roughness length z o and resistance to¯ow f. The results indicate that low sediment concentration aects mainly the near bed portion of the¯ow where it causes a reduction of mean¯ow velocity and an increase of shear velocity and roughness length. For larger sediment concentration, the whole¯ow velocity pro®le becomes aected by bedload roughness but the importance of this eect always remain larger near the bed. As sediment concentration is augmented, mean¯ow velocity is consistently reduced but shear velocity and roughness length increase until a plateau is reached where these two variables become constant.

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Section: Discussionsupporting

confidence: 86%

Section: Introductionmentioning

confidence: 99%

The effect of sediment concentration on bedload roughness

Bergeron

Carbonneau

1999

Hydrol. Process.

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“…This is despite the fact that experimental studies have shown measurable increases in the friction factor due to the bed load transport in both pipes and open channel flows (Song et al, 1998;Gao and Abrahams, 2004).…”

Section: -------------------------------mentioning

confidence: 94%

“…Bagnold ( (7.5) Song et al (1998) and Gao and Abrahams (2004) investigated the flow resistance (energy dissipation) caused by bed load movement in flumes under plane bed conditions with no suspended sediment transport. They found that flow resistance increased as either sediment concentration or sediment size increased and demonstrated that the contribution of bed load transport to overall flow resistance could be as great as that due to grain roughness.…”

Section: -------------------------------mentioning

confidence: 99%

Morphological Response of the Brahmaputra–Padma–Lower Meghna River System to the Assam Earthquake of 1950

Sarker

Thorne

2006

Braided Rivers

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Sediment rating curves Chapter 6 Conceptual model 174 6.1 Introduction 6.2 Celerity of the disturbance in a riverbed 6.3 Changes in the Independent Variables 6.3.1 Changes in the flow regime 6.3.2 Changes in bed sediment size 6.3.3 Changes in the sediment regime 6.4 Changes in the Dependent Variables 6.4.1 Changes in bed elevation 6.4.2 Changes in width 6.4.3 Changes in braiding intensity 6.4.4 Phase lags in the observed morphological changes 65 Development of the conceptual process-response model.. 201 6.5.1 Background 201 6.5.2Adjustments in the upstream reach of the Jamuna River 202 6.5.3 Downstream reach of the

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“…From the viewpoint of the physics of flow, it is intuitive that because of slip or motion of the bed particles, the resistance to the flowing fluid from a mobile bed is always less than that from an immobile bed. Thus, the contradictory findings of Song et al (1994Song et al ( , 1998, who argued that the friction factor increases with sediment transport may invite uncertainty. They calculated u Ã from the bed slopes, suggesting that the calculation of u Ã from the bed slopes is valid only for immobile beds and cannot truly predict u Ã for mobile beds because the original derivation of u Ã ¼ ðghSÞ 0:5 is based on a rigid wall (Streeter and Wylie 1983).…”

Section: Time-averaged Velocity and Reynolds Shear Stressmentioning

confidence: 96%

Near-Bed Turbulence Characteristics at the Entrainment Threshold of Sediment Beds

2011

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This experimental study is devoted to quantification of the near-bed turbulence characteristics at an entrainment threshold of noncohesive sediments. Near the bed, the departure in the distributions of the observed time-averaged streamwise velocity from the logarithmic law is more for immobile beds than for entrainment-threshold beds. In the Reynolds shear stress distributions, a damping that occurs near the bed for sediment entrainment is higher than that for immobile beds. Quadrant analysis reveals that in the near-bed flow zone, ejections and sweeps on immobile beds cancel each other, giving rise to the outward interactions, whereas sweeps are the dominant mechanism toward sediment entrainment. The bursting duration for entrainment-threshold beds is smaller than that for immobile beds. On the other hand, the bursting frequency for entrainment-threshold beds is larger than that for immobile beds. The third-order correlations indicate that during sediment entrainment, a streamwise acceleration associated with a downward flux and advection of streamwise Reynolds normal stress is prevalent. The streamwise and the downward vertical fluxes of turbulent kinetic energy (TKE) increase with sediment entrainment. The TKE budget proves that for sediment entrainment, the pressure energy diffusion changes drastically to a negative magnitude, indicating a gain in turbulence production.

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Effect of Bed-Load Movement on Flow Friction Factor

Cited by 69 publications

References 13 publications

The effect of sediment concentration on bedload roughness

The effect of sediment concentration on bedload roughness

Morphological Response of the Brahmaputra–Padma–Lower Meghna River System to the Assam Earthquake of 1950

Near-Bed Turbulence Characteristics at the Entrainment Threshold of Sediment Beds

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