The Uncertainty of Measurements in River Hydraulics: Evaluation of Friction Velocity Based on an Unrepeatable Experiment

Mrokowska, Magdalena M.; Rowiński, Paweł M.; Kalinowska, Monika B.

doi:10.1007/978-3-642-30209-1_13

Cited by 4 publications

(8 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Friction velocity is usually applied to further calculations, and for this reason information about the uncertainty of results is of high importance. In the case of unrepeatable experiments Mrokowska et al (2013) have suggested applying ::::::::::: deterministic :::::::: approach : -: the law of propagation of uncertainty (Holman, 2001;Fornasini, 2008), which for Eq. 15 In 4.…”

Section: Uncertainty Of Input Data and The Resultsmentioning

confidence: 99%

“…Data set Ol-1 was applied in (Mrokowska and Rowiński, 2012;Rowiński et al, 2000), and data set Ol-4 in (Mrokowska et al, 2013), and to the authors knowledge, none of the data sets have been utilised elsewhere in the context of the evaluation of friction velocity.…”

Section: Experimental Datamentioning

confidence: 99%

“…Aricó et al (2009) have pointed that this may be the case for mild and small bed slopes. Moreover, artificial flood waves, such as dam-break-like waves (Mrokowska et al, 2013), and waves due to hydro-peaking (Shen and Diplas, 2010;Spiller et al, 2014), are of a dynamic character. On the other hand, when the bed slope is large, then the gravity force dominates and the wave is kinematic (Aricó et al, 2009).…”

Section: Formulae For Friction Velocitymentioning

confidence: 99%

“…The bulk friction velocity for a dynamic wave in a trapezoidal channel may be evaluated from the relation derived from the St. Venant model (Eqs. 13and 14:: 13 ::: and ::: 14) (Mrokowska et al, 2013). The cross sectional shape with symbols is depicted in Fig.…”

Section: Formulae For Friction Velocitymentioning

confidence: 99%

See 3 more Smart Citations

Notes on the estimation of resistance to flow during flood wave propagation

Mrokowska¹,

Rowiński²,

Kalinowska³

2014

Preprint

View full text Add to dashboard Cite

Abstract. The paper discusses methods of expressing and evaluating resistance to flow in an unsteady flow. Following meaningful trends in hydrological sciences, the paper suggests abandoning, where possible, resistance coefficients in favour of physically based variables such as shear stress and friction velocity. Consequently, an acknowledged method of friction velocity evaluation based on the relations derived from flow equations is examined. The paper presents both a theoretical discussion of various aspects of friction velocity evaluation and the application of the method to field data originating from artificial dam-break flood waves in a small lowland river. As the method is prone to many errors due to the scarcity and the uncertainty of measurement data, the aim of the paper is to provide suggestions on how to apply the method to enhance the correctness of the results. The main steps in applying the method include consideration of the shape of the channel, the type of wave, the method of evaluating the gradient of the flow depth, and the assessment of the uncertainty of the result. Friction velocity and the Manning coefficient are compared in terms of resistance to flow variability during flood wave propagation. It is concluded that the Manning coefficient may be a misleading indicator of the magnitude of resistance in unsteady flow, and to be inferior to physically based variables in such cases.

show abstract

Section: Uncertainty Of Input Data and The Resultsmentioning

confidence: 99%

Section: Experimental Datamentioning

confidence: 99%

Section: Formulae For Friction Velocitymentioning

confidence: 99%

Section: Formulae For Friction Velocitymentioning

confidence: 99%

See 2 more Smart Citations

Notes on the estimation of resistance to flow during flood wave propagation

Mrokowska¹,

Rowiński²,

Kalinowska³

2014

Preprint

View full text Add to dashboard Cite

show abstract

“…Thus, the approximation that R is approximated as h-as adopted in this study-is reasonable. On the other hand, objective unsteady friction is related to the temporal and spatial change rates of mean cross-sectional velocity and flow depth [4,5,7,34]. This shows that it is feasible to improve the 1D friction model structure using terms relating to nonuniform and nonsteady characteristics.…”

Section: Single-factor Analysismentioning

confidence: 99%

A Hydraulic Friction Model for One-Dimensional Unsteady Channel Flows with Experimental Demonstration

Bao

Zhou

Xiang

et al. 2018

Water

View full text Add to dashboard Cite

Abstract:As a critical parameter of the steady uniform friction model, the roughness coefficient changes with flow unsteadiness in flood events; i.e., the flow conditions of the stream segment significantly affect the flow resistance. In this study, a modified formula was established to improve the unsteady friction simulation; ten terms relating to the first-and second-order time and space partial derivatives of hydraulic parameters were selected as additional terms. The results of a hydraulic experiment show that the hysteresis between flow depth and mean cross-sectional velocity cannot be neglected in unsteady flows that disturb the performance of a steady uniform friction model. Six terms have a strong correlation with objective friction. Further, three of them have a small variance in correlation coefficient. Then, the composition of the proposed formula was determined. The results show that adding too many additional terms provides better performance in the calibration phase, yet reduces the accuracy of the validation phase because of an overfitting phenomenon. The optimal number of additional terms is three, and the established formula can improve the unsteady friction simulation.

show abstract

Bed Shear Stress and Near‐Bed Flow Through Sparse Arrays of Rigid Emergent Vegetation

Aliaga,

Aberle

2024

Water Resources Research

View full text Add to dashboard Cite

Vegetation is an essential component of natural rivers and has significant effects on flow and morphodynamic processes. Although progress has been made in characterizing flow resistance in vegetated flows, the impact of vegetation on bed shear stress, a key driver of sediment transport, still needs better characterization and understanding. This research, explores bed shear stress and near‐bed flow characteristics in sparse arrays of rigid emergent cylinders mimicking vegetation over a rough bed. For this purpose, a novel adaptation of a shear plate was used to measure bed shear stress at the canopy scale. These measurements were analyzed in relation to spatially averaged near‐bed flow quantities for different array densities. The results show that, for a constant water depth, the investigated cylinder canopy enhances the ratio between bed shear stress and bulk flow velocity (i.e., Darcy‐Weisbach bed friction factor) compared to unobstructed open‐channel flows, and that this ratio increases with array density. Moreover, higher near‐bed velocities were observed for higher array densities. On the other hand, no influence of the cylinder array on near‐bed values of turbulent kinetic energy and turbulent stresses was observed. Finally, it is shown that the thickness of the near‐bed layer is a suitable parameter to scale the ratio between bed shear stress and bulk flow velocity in vegetated rough bed flows.

show abstract

The Uncertainty of Measurements in River Hydraulics: Evaluation of Friction Velocity Based on an Unrepeatable Experiment

Cited by 4 publications

References 19 publications

Notes on the estimation of resistance to flow during flood wave propagation

Notes on the estimation of resistance to flow during flood wave propagation

A Hydraulic Friction Model for One-Dimensional Unsteady Channel Flows with Experimental Demonstration

Bed Shear Stress and Near‐Bed Flow Through Sparse Arrays of Rigid Emergent Vegetation

Contact Info

Product

Resources

About