The Origin of Fine Sediment Determines the Observations of Suspended Sediment Fluxes Under Unsteady Flow Conditions

2018 ◽  
Vol 54 (8) ◽  
pp. 5654-5669 ◽  
Author(s):  
Carmelo Juez ◽  
Marwan A. Hassan ◽  
Mário J. Franca
Keyword(s):  
Unsteady Flow ◽  
Suspended Sediment ◽  
Fine Sediment ◽  
Flow Conditions ◽  
Sediment Fluxes

scholarly journals Sub-daily variability of suspended sediment fluxes in small mountainous catchments – implications for community-based river monitoring

2010 ◽  
Vol 7 (5) ◽  
pp. 8233-8263
Author(s):  
C. Duvert ◽  
N. Gratiot ◽  
J. Némery ◽  
A. Burgos ◽  
O. Navratil
Keyword(s):  
Suspended Sediment ◽  
Rural Areas ◽  
Temporal Variability ◽  
Fine Sediment ◽  
Community Based ◽  
Sediment Yields ◽  
Sediment Fluxes ◽  
Monitoring Strategies ◽  
Mountainous Catchments ◽  
Daily Variability

Abstract. Accurate estimates of suspended sediment yields depend on effective monitoring strategies. In mountainous environments undergoing intense seasonal precipitation, the implementation of such monitoring programs relies primarily on a rigorous study of the temporal variability of fine sediment transport. This investigation focuses on seasonal and short-term sediment variability in a subhumid region of the Mexican Volcanic Belt. Intensive hydrosedimentary monitoring was conducted during one year on four contrasting catchments (3 to 630 km2). Analyses revealed significant temporal variability in suspended sediment export over various time scales, with between 63 and 97% of the annual load exported in as little as 2% of the time. Statistical techniques were used to evaluate the sampling frequency required to get reliable annual sediment yield estimates at the four sites. A bi-daily sampling would be required at the outlet of the 630-km2 catchment, whereas in the three smaller catchments (3–12 km2), the achievement of accurate estimates would inevitably require hourly monitoring. At the larger catchment scale, analysis of the sub-daily variability of fine sediment fluxes showed that the frequency of sampling could be lowered by up to 100% (i.e. from bi-daily to daily) if considering a specific and regular sampling time in the day. In contrast, conducting a similar sampling strategy at the three smaller catchments could lead to serious misinterpretation (i.e. up to 1000% error). Our findings emphasise the importance of an analysis of the sub-daily variability of sediment fluxes in mountainous catchments. Characterising this variability may offer useful insights for improving the effectiveness of community-based monitoring strategies in rural areas of developing countries. In regions where historical records based on discrete sampling are available, it may also help assessing the quality of past flux estimates. Finally, the study confirms the global necessity of acquiring more high frequency data in small mountainous catchments, especially in poorly gauged areas.

scholarly journals Sub-daily variability of suspended sediment fluxes in small mountainous catchments &ndash implications for community-based river monitoring

2011 ◽  
Vol 15 (3) ◽  
pp. 703-713 ◽  
Author(s):  
C. Duvert ◽  
N. Gratiot ◽  
J. Némery ◽  
A. Burgos ◽  
O. Navratil
Keyword(s):  
Suspended Sediment ◽  
Temporal Variability ◽  
Fine Sediment ◽  
Sediment Flux ◽  
Community Based ◽  
Sediment Yields ◽  
Sediment Fluxes ◽  
Monitoring Strategies ◽  
Mountainous Catchments ◽  
Daily Variability

Abstract. Accurate estimates of suspended sediment yields depend on effective monitoring strategies. In mountainous environments undergoing intense seasonal precipitation, the implementation of such monitoring programs relies primarily on a rigorous study of the temporal variability of fine sediment transport. This investigation focuses on seasonal and short-term variability in suspended sediment flux in a subhumid region of the Mexican Volcanic Belt. Intensive monitoring was conducted during one year in four contrasting catchments (3 to 630 km2). Analyses revealed significant temporal variability in suspended sediment export over various time scales, with between 63 and 97% of the annual load exported in as little as 2% of the time. Statistical techniques were used to evaluate the sampling frequency required to get reliable estimates of annual sediment yield at the four sites. A bi-daily sampling scheme would be required at the outlet of the 630 km2 catchment, whereas in the three smaller catchments (3–12 km2), accurate estimates would inevitably require hourly monitoring. At the larger catchment scale, analysis of the sub-daily variability of fine sediment fluxes showed that the frequency of sampling could be lowered by up to 100% (i.e. from bi-daily to daily) if a specific and regular sampling time in the day was considered. In contrast, conducting a similar sampling strategy at the three smaller catchments could lead to serious misinterpretation (i.e. up to 1000% error). Our findings emphasise the importance of an analysis of the sub-daily variability of sediment fluxes in mountainous catchments. Characterising this variability may offer useful insights for improving the effectiveness of community-based monitoring strategies in rural areas of developing countries. In regions where historical records based on discrete sampling are available, it may also help assessing the quality of past flux estimates. Finally, the study confirms the global necessity of acquiring more high frequency data in small mountainous catchments, especially in poorly gauged areas.

The Estimation of Discharge in an Experimental Open Channel

2014 ◽  
Vol 905 ◽  
pp. 369-373
Author(s):  
Choo Tai Ho ◽  
Yoon Hyeon Cheol ◽  
Yun Gwan Seon ◽  
Noh Hyun Suk ◽  
Bae Chang Yeon
Keyword(s):  
Unsteady Flow ◽  
River Discharge ◽  
Open Channel ◽  
Flow Conditions ◽  
Mean Velocity ◽  
Velocity Equation ◽  
The Mean ◽  
Loop Form

The estimation of a river discharge by using a mean velocity equation is very convenient and rational. Nevertheless, a research on an equation calculating a mean velocity in a river was not entirely satisfactory after the development of Chezy and Mannings formulas which are uniform equations. In this paper, accordingly, the mean velocity in unsteady flow conditions which are shown loop form properties was estimated by using a new mean velocity formula derived from Chius 2-D velocity formula. The results showed that the proposed method was more accurate in estimating discharge, when compared with the conventional formulas.

Computational Study of the Risø-B1-18 Airfoil with a Hinged Flap Providing Variable Trailing Edge Geometry

2005 ◽  
Vol 29 (2) ◽  
pp. 89-113 ◽  
Author(s):  
Niels Troldborg
Keyword(s):  
Reynolds Number ◽  
Unsteady Flow ◽  
Computational Study ◽  
Turbine Blades ◽  
Aerodynamic Characteristics ◽  
Flow Conditions ◽  
Wind Turbine Blades ◽  
Trailing Edge ◽  
Edge Geometry ◽  
Fully Developed Turbulent Flow

A comprehensive computational study, in both steady and unsteady flow conditions, has been carried out to investigate the aerodynamic characteristics of the Risø-B1-18 airfoil equipped with variable trailing edge geometry as produced by a hinged flap. The function of such flaps should be to decrease fatigue-inducing oscillations on the blades. The computations were conducted using a 2D incompressible RANS solver with a k-w turbulence model under the assumption of a fully developed turbulent flow. The investigations were conducted at a Reynolds number of Re = 1.6 · 106. Calculations conducted on the baseline airfoil showed excellent agreement with measurements on the same airfoil with the same specified conditions. Furthermore, a more widespread comparison with an advanced potential theory code is presented. The influence of various key parameters, such as flap shape, flap size and oscillating frequencies, was investigated so that an optimum design can be suggested for application with wind turbine blades. It is concluded that a moderately curved flap with flap chord to airfoil curve ratio between 0.05 and 0.10 would be an optimum choice.

Competitive flow and anastomosis angle influence on bypass hemodynamics in unsteady flow conditions

2017 ◽  
Author(s):  
A. F. Totorean ◽  
S. I. Bernad ◽  
I. C. Hudrea ◽  
R. F. Susan-Resiga
Keyword(s):  
Unsteady Flow ◽  
Flow Conditions

scholarly journals Fractal derivative model for the transport of the suspended sediment in unsteady flows

2018 ◽  
Vol 22 (Suppl. 1) ◽  
pp. 109-115 ◽  
Author(s):  
Shiqian Nie ◽  
Hong Sun ◽  
Xiaoting Liu ◽  
Wang Ze ◽  
Mingzhao Xie
Keyword(s):  
Vertical Distribution ◽  
Unsteady Flow ◽  
Suspended Sediment ◽  
Suspended Sediment Concentration ◽  
Spatial Location ◽  
Sediment Concentration ◽  
Equation Model ◽  
Advection Dispersion ◽  
Fractal Derivative ◽  
The Vertical Distribution

This paper makes an attempt to develop a Hausdorff fractal derivative model for describing the vertical distribution of suspended sediment in unsteady flow. The index of Hausdorff fractal derivative depends on the spatial location and the temporal moment in sediment transport. We also derive the approximate solution of the Hausdorff fractal derivative advection-dispersion equation model for the suspended sediment concentration distribution, to simulate the dynamics procedure of suspended concentration. Numerical simulation results verify that the Hausdorff fractal derivative model provides a good agreement with the experimental data, which implies that the Hausdorff fractal derivative model can serve as a candidate to describe the vertical distribution of suspended sediment concentration in unsteady flow.

Suspended sediment fluxes in a tidal wetland: Measurement, controlling factors, and error analysis

Estuaries ◽  
2005 ◽  
Vol 28 (6) ◽  
pp. 812-822 ◽  
Author(s):  
Neil K. Ganju ◽  
David H. Schoellhamer ◽  
Brian A. Bergamaschi
Keyword(s):  
Error Analysis ◽  
Suspended Sediment ◽  
Controlling Factors ◽  
Tidal Wetland ◽  
Sediment Fluxes
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