Flow resistance in mobile bed rills shaped in soils with different texture

2021 ◽  
Author(s):  
Francesco G. Carollo ◽  
Costanza Di Stefano ◽  
Alessio Nicosia ◽  
Vincenzo Palmeri ◽  
Vincenzo Pampalone ◽  
...  
Keyword(s):  
Flow Resistance ◽  
Mobile Bed

scholarly journals Roughness Effect of Submerged Groyne Fields with Varying Length, Groyne Distance, and Groyne Types

Water ◽  
2019 ◽  
Vol 11 (6) ◽  
pp. 1253 ◽  
Author(s):  
Ronald Möws ◽  
Katinka Koll
Keyword(s):  
Flow Resistance ◽  
Relative Increase ◽  
Design Guidelines ◽  
Water Levels ◽  
Constant Field ◽  
Initial Water ◽  
Mobile Bed ◽  
Wake Interference ◽  
Backwater Effect ◽  
Varying Length

Design guidelines were developed for a number of in-stream structures; however, the knowledge about their morphological and hydraulic function is still incomplete. A variant is submerged groynes, which aim to be applicable for bank protection especially in areas with restricted flood water levels due to their shallow height. Laboratory experiments were conducted to investigate the backwater effect and the flow resistance of submerged groyne fields with varying and constant field length and groyne distance. The effect of the shape of a groyne model was investigated using two types of groynes. The validity of different flow types, from “isolated roughness” to “quasi smooth”, was analyzed in relation to the roughness density of the groyne fields. The results show a higher backwater effect for simplified groynes made of multiplex plates, compared to groynes made of gravel. The relative increase of the upstream water level was lower at high initial water levels, for short length of the groyne field, and for larger distance between the single groynes. The highest roughness of the groyne fields was found at roughness densities, which indicated wake interference flow. Considering a mobile bed, the flow resistance was reduced significantly.

Testing slope effect on flow resistance equation for mobile bed rills

2018 ◽  
Vol 32 (5) ◽  
pp. 664-671 ◽  
Author(s):  
Costanza Di Stefano ◽  
Vito Ferro ◽  
Vincenzo Palmeri ◽  
Vincenzo Pampalone
Keyword(s):  
Flow Resistance ◽  
Mobile Bed ◽  
Resistance Equation

scholarly journals Influence of riparian vegetation on flow resistance in mobile bed straight compound channels

2018 ◽  
Vol 1049 ◽  
pp. 012027 ◽  
Author(s):  
M Jumain ◽  
Z Ibrahim ◽  
Z Ismail ◽  
K Entalai ◽  
M R Makhtar ◽  
...  
Keyword(s):  
Riparian Vegetation ◽  
Flow Resistance ◽  
Compound Channels ◽  
Mobile Bed

scholarly journals FLOW RESISTANCE IN MOBILE-BED RIVERS

1984 ◽  
Vol 1984 (342) ◽  
pp. 15-21
Author(s):  
Sachio OZAKI ◽  
Takeshi ISHIBASHI ◽  
Takao SHIRASUNA
Keyword(s):  
Flow Resistance ◽  
Mobile Bed

Comparing flow resistance law for fixed and mobile bed rills

2019 ◽  
Vol 33 (26) ◽  
pp. 3330-3348 ◽  
Author(s):  
Costanza Di Stefano ◽  
Alessio Nicosia ◽  
Vincenzo Palmeri ◽  
Vincenzo Pampalone ◽  
Vito Ferro
Keyword(s):  
Flow Resistance ◽  
Mobile Bed

Experiments for testing soil texture effects on flow resistance in mobile bed rills

CATENA ◽  
2018 ◽  
Vol 171 ◽  
pp. 176-184 ◽  
Author(s):  
Vincenzo Palmeri ◽  
Vincenzo Pampalone ◽  
Costanza Di Stefano ◽  
Alessio Nicosia ◽  
Vito Ferro
Keyword(s):  
Soil Texture ◽  
Flow Resistance ◽  
Mobile Bed

scholarly journals Rill flow resistance law under sediment transport

2021 ◽  
Author(s):  
Costanza Di Stefano ◽  
Alessio Nicosia ◽  
Vincenzo Palmeri ◽  
Vincenzo Pampalone ◽  
Vito Ferro
Keyword(s):  
Sediment Transport ◽  
Flow Velocity ◽  
Friction Factor ◽  
Flow Resistance ◽  
Fixed Bed ◽  
Accurate Estimate ◽  
Mean Flow ◽  
Mobile Bed ◽  
Resistance Equation ◽  
Rill Flow

Abstract Purpose In this paper, a deduced flow resistance equation for open-channel flow was tested using measurements carried out in mobile bed rills with sediment-laden flows and fixed bed rills. The main aims were to (i) assess the effect of sediment transport on rill flow resistance, and (ii) test the slope-flow velocity relationship in fixed bed rills. Methods The following analysis was developed: (i) a relationship between the Γ function of the velocity profile, the rill slope and the Froude number was calibrated using measurements carried out on fixed bed rills; (ii) the component of Darcy-Weisbach friction factor due to sediment transport was deduced using the corresponding measurements carried out on mobile bed rills (grain resistance and sediment transport) and the values estimated by flow resistance equation (grain resistance) for fixed bed rills in the same slope and hydraulic conditions; (iii) the Γ function relationship was calibrated using measurements carried out on mobile bed rills and the data of Jiang et al. (2018). Results This analysis demonstrated that the effect of sediment transport on rill flow resistance law is appreciable only for 7.7% of the examined cases and that the theoretical approach allows for an accurate estimate of the Darcy-Weisbach friction factor. Furthermore, for both fixed and mobile beds, the mean flow velocity was independent of channel slope, as suggested by Govers (1992) for mobile bed rills. Conclusions The investigation highlighted that the effect of sediment transport on rill flow resistance is almost negligible for most of the cases and that the experimental procedure for fixing rills caused the unexpected slope independence of flow velocity.

The influence of planform on flow resistance in mobile bed compound channels

2001 ◽  
Vol 148 (1) ◽  
pp. 5-14 ◽  
Author(s):  
J. F. Lyness ◽  
W. R. C. Myers ◽  
J. B. C. Cassells ◽  
J. J. O'Sullivan
Keyword(s):  
Flow Resistance ◽  
Compound Channels ◽  
Mobile Bed

Drag and Turbulent Characteristics of Mobile Bed Channel With Mixed Vegetation Densities Under Downward Seepage

2016 ◽  
Vol 138 (7) ◽  
Author(s):  
Thokchom Bebina Devi ◽  
Rishabh Daga ◽  
Sumit Kumar Mahto ◽  
Bimlesh Kumar
Keyword(s):  
Drag Coefficient ◽  
Reynolds Stress ◽  
Flow Resistance ◽  
Flow Characteristics ◽  
Vegetation Density ◽  
Streamwise Direction ◽  
Mobile Bed ◽  
Downward Seepage ◽  
Turbulent Characteristics ◽  
Sediment Particles

The present study addresses the drag owing to the presence of vegetation and turbulent characteristics in a mobile bed channel, characterized by fully submerged vegetation formed by nonuniform vegetation densities. The influence of seepage on the velocity profiles, Reynolds stress, and turbulence intensities is discussed. Experimental results show that vegetation density is one of the important parameters that affect the flow resistance. It is found that higher vegetation density when placed at the downstream side leads to a reduction in velocity, Reynolds stress, and turbulent intensities. Downward seepage increases the near bed velocity, Reynolds stress, and turbulent intensities. Moment analysis shows that there is an increase in the inrush of flow, and sediment particles are transported more toward the streamwise direction with the application of seepage. The dominance of sweep events over ejection events increases more sediment transport. However, high vegetation density when placed at the downstream portion slightly decreases the dominance of sweep event. Drag coefficient decreases near the vegetation top and increases near the bed. Downward seepage decreases the effect of drag offered by the vegetation stems. The reduction in flow characteristics, viz., velocity, Reynolds stress, turbulent intensities, in the downstream portion of lesser spacing vegetation stems is attributed an increased drag coefficient.

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