Experimental Study of the Coarse Surface Development Effect on the Bimodal Bed-Load Transport under Unsteady Flow Conditions

Güney, Mehmet Şükrü; Bombar, Gökçen; Aksoy, Aysegul Ozgenc

doi:10.1061/(asce)hy.1943-7900.0000640

Cited by 42 publications

(70 citation statements)

References 16 publications

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“…These methods are impractical or even impossible to be applied during flood wave propagation. Instead, a number of authors recommend formulae derived from flow equations (Ghimire and Deng, 2011;Graf and Song, 1995;Guney et al, 2013;Rowiński et al, 2000); nonetheless, this method needs further development because scarce measurement data very often restrict the relationships on resistance to simplified forms which provide uncertain results. Among simplifications applied in literature there are simplifications of momentum balance equation terms and simplifications that refer to the evaluation of the gradient of flow depth.…”

Section: M Mrokowska Et Al: a Methodological Approach Of Estimatmentioning

confidence: 99%

A methodological approach of estimating resistance to flow under unsteady flow conditions

Mrokowska

Rowiński

Kalinowska

2015

Hydrol. Earth Syst. Sci.

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Abstract. This paper presents an evaluation and analysis of resistance parameters: friction slope, friction velocity and Manning coefficient in unsteady flow. The methodology to enhance the evaluation of resistance by relations derived from flow equations is proposed. The main points of the methodology are (1) to choose a resistance relation with regard to a shape of a channel and (2) type of wave, (3) to choose an appropriate method to evaluate slope of water depth, and (4) to assess the uncertainty of result. In addition to a critical analysis of existing methods, new approaches are presented: formulae for resistance parameters for a trapezoidal channel, and a translation method instead of Jones' formula to evaluate the gradient of flow depth. Measurements obtained from artificial dam-break flood waves in a small lowland watercourse have made it possible to apply the method and to analyse to what extent resistance parameters vary in unsteady flow. The study demonstrates that results of friction slope and friction velocity are more sensitive to applying simplified formulae than the Manning coefficient (n). n is adequate as a flood routing parameter but may be misleading when information on trend of resistance with flow rate is crucial. Then friction slope or friction velocity seems to be better choice.

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Section: M Mrokowska Et Al: a Methodological Approach Of Estimatmentioning

confidence: 99%

A methodological approach of estimating resistance to flow under unsteady flow conditions

Mrokowska

Rowiński

Kalinowska

2015

Hydrol. Earth Syst. Sci.

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“…It is, in fact, a subject of ongoing debate and multiple interpretations (Guney et al, 2013;Mao et al, 2011;Mrokowska et al, 2016).…”

Section: Evaluation Of Bed Shear Stress and Stream Powermentioning

confidence: 99%

“…Bombar et al (2011) reported an anti-clockwise hysteresis in experiments with a static armour layer, where the maximum bedload transport was possible only after the peak flowrate, when the armour layer was destroyed by a high flow. When sediment is heterogeneous, sediment transport is affected by grain arrangement (Ockelford and Haynes, 2013): microforms (clusters) are formed (Mao, 2012), static or mobile armour layer appears (Guney et al, 2013), and partial transport may take place (Sun et al, 2015). To make things more complicated, bedload transport is additionally controlled by the availability of upstream sediment in supply-limited rivers (Mao et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

“…They varied in terms of various factors, such as the shape of unsteady flow hydrograph, e.g., triangular (Lee et al, 2004), trapezoidal (Bombar et al, 2011), step-wise (Mao, 2012), naturally shaped (Humphries et al, 2012); bed composition -uni-modal or bimodal (Wang et al, 2015); supply of sediment from upstream (Mao, 2012); initial bed conditions -armoured bed (Bombar et al, 2011) and not armoured bed (Humphries et al, 2012), or duration of flow from a few minutes (Guney et al, 2013) to a few hours (Mao, 2012). Some studies took into account or commented on scaling from natural to laboratory conditions, e.g., (Cooper and Tait, 2009;Wang et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

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Laboratory studies on bedload transport under unsteady flow conditions

Mrokowska

Rowiński

Książek

et al. 2017

Journal of Hydrology and Hydromechanics

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Two sets of triangular hydrographs were generated in a 12-m-long laboratory flume for two sets of initial bed conditions: intact and water-worked gravel bed. Flowrate ranging from 0.0013 m 3 s -1 to 0.0456 m 3 s -1 , water level ranging from 0.02 m to 0.11 m, and cumulative mass of transported sediment ranging from 4.5 kg to 14.2 kg were measured. Then, bedload transport rate, water surface slope, bed shear stress, and stream power were evaluated. The results indicated the impact of initial bed conditions and flow unsteadiness on bedload transport rate and total sediment yield. Difference in ratio between the amount of supplied sediment and total sediment yield for tests with different initial conditions was observed. Bedload rate, bed shear stress, and stream power demonstrated clock-wise hysteretic relation with flowrate. The study revealed practical aspects of experimental design, performance, and data analysis. Water surface slope evaluation based on spatial water depth data was discussed. It was shown that for certain conditions stream power was more adequate for the analysis of sediment transport dynamics than the bed shear stress. The relations between bedload transport dynamics, and flow and sediment parameters obtained by dimensional and multiple regression analysis were presented.

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“…While those studies are all based on steady flow, limited research has been performed to investigate the effect of unsteadiness in free surface flows. Some unsteady flow experiments focus on velocity measurements, sediment transport behavior or studied the river as an ecosystem [3,[12][13][14][15][16][17]. Others address different types of flows, like gravity currents [18,19].…”

Section: Introductionmentioning

confidence: 99%

Dynamic Lift on an Artificial Static Armor Layer During Highly Unsteady Open Channel Flow

Spiller

Rüther

Friedrich

2015

Water

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Abstract:The dynamic lift acting on a 100 mm × 100 mm section of a static armor layer during unsteady flow is directly measured in a series of physical experiments. The static armor layer is represented by an artificial streambed mold, made from an actual gravel bed. Data from a total of 190 experiments are presented, undertaken in identical conditions. Results show that during rapid discharge increases, the dynamic lift on the streambed repeatedly exhibits three clear peaks. The magnitude of the observed lift depends on the following hydrograph characteristics: (1) the initial flow depth; (2) the ramping duration and therefore the ramping rate; and (3) the total discharge increase. An adjusted unsteadiness parameter combines those three hydrograph characteristics for rapid discharge increases. Direct correlations between the unsteadiness parameter and the measured dynamic lift during unsteady flow are presented. In addition, the armor layer porosity showed a major impact on the observed effects. It is shown that increasing bed porosity leads to decreasing dynamic lift.

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Experimental Study of the Coarse Surface Development Effect on the Bimodal Bed-Load Transport under Unsteady Flow Conditions

Cited by 42 publications

References 16 publications

A methodological approach of estimating resistance to flow under unsteady flow conditions

A methodological approach of estimating resistance to flow under unsteady flow conditions

Laboratory studies on bedload transport under unsteady flow conditions

Dynamic Lift on an Artificial Static Armor Layer During Highly Unsteady Open Channel Flow

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