Search results for "Friction factor"
showing 10 items of 11 documents
Comment on “Rill erosion processes on steep colluvial deposit slope under heavy rainfall in flume experiments with artificial rain by F. Jiang et al.”
2020
Abstract Since rill flows are characterized by small water depths and steeply sloping channels, the corresponding hydraulic conditions are very different to those which are typically found in channels of streams and rivers. Furthermore, limited information is currently available on the effect of rainfall on flow resistance. The objective of this comment was to investigate the applicability of a recently theoretically deduced rill flow resistance equation, based on a power-velocity profile, using measurements carried out by Jiang et al. for both different slope steepness conditions and rainfall intensity. The relationship between the velocity profile parameter Γ, the channel slope and the fl…
Application of a 1-D numerical model to estimate the sediment transported along a river
2006
Natural rivers tend to adjust their plane shape and longitudinal profile in order to assume a configuration compatible with the changing hydraulic and man-made constraints. The causes of these bed variations are related to changes in independent river channel variables (increase in water discharge, decrease in sediment discharge, etc..) or to changes in river slope. River bed degradation and aggradation, often occurring as result of river morphological changes, modify the longitudinal bed profile of the river and the amount of sediment transported along the river until to reach the outlet. As an example, the construction of river dams produces large morphological consequences: when the stre…
A theoretically-based overland flow resistance law for upland grassland habitats
2022
Abstract Sediments conveyed from interrill areas to rills are transported by a thin flow (overland flow) and the knowledge of overland flow resistance is useful to evaluate overland flow velocity and sediment transport capacity. The aim of this paper was to verify the applicability of a theoretical overland flow resistance law, based on a power-velocity distribution, using field measurements for four upland grassland types used in different management strategies (Hay Meadows, Low-density Grazing, Rushes and Rank Grassland). Particular attention was deserved to the effects of vegetation growth cycles on the surface roughness and the corresponding reduction of overland flow velocity. The rela…
Comments on “Measurement of dimensionless Chezy coefficient in step-pool reach (Case study of Dizin River in Iran)” by Torabizadeh A., Tahershamsi A.…
2018
This paper is a comment on a previous published paper.
Flow Resistance in Step-Pool Rills
2017
Rills evolve morphologically, and the adjustment of rill channel geometry to flow affects the relationships among velocity, discharge, and slope. The resistance to flow in step-pool rills is mainly due to form-induced mechanisms and, in comparison, grain resistance is of minor significance. Previous studies on rill flow resistance have been performed exclusively for grainresistance conditions and use a stream flow equation. In this study, a new flow resistance equation, deduced by applying dimensional analysis and self-similarity theory, was applied to rill flow in step-pool channels. First, the incomplete self-similarity hypothesis was used for establishing a power flow velocity profile wh…
Rill flow resistance law under sediment transport
2021
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 measurem…
Flow Resistance Law in Channels with Flexible Submerged Vegetation
2005
In this paper, experimental data collected in a straight flume having a bed covered by grasslike vegetation have been used to analyze flow resistance for flexible submerged elements. At first, the measurements are used to test the applicability of Kouwen’s method. Then, a calibration of two coefficients appearing in the semilogarithmic flow resistance equation is carried out. Finally, applying the P-theorem and the incomplete self-similarity condition, a flow resistance equation linking the friction factor with the shear Reynolds number, the depth-vegetation height ratio and the inflection degree is deduced.
Experimental and Numerical Study on the Flow Field and Friction Factor in a Pressurized Corrugated Pipe
2015
An experimental campaign including measurement of pressure drops and velocity profiles was conducted on the pressurized flow in a commercial corrugated pipe. The results show that the empirical graphs suggested by Morris in the fifties may produce inaccurate assessments of the friction factor, in particular, for low Reynolds numbers. The experimental data was then reproduced by means of a numerical model with the large eddy simulation (LES) technique. The friction factor behavior for low and relatively high Reynolds numbers was thus investigated. The numerical simulations were in good agreement with the experimental results, showing the LES suitability to predict the effect of the pipe wall…
Analysis of Geometrical Relationships and Friction Losses in Small-Diameter Lay-Flat Polyethylene Pipes
2016
[EN] The use of lay-flat polyethylene pipes to irrigate horticultural crops has been receiving widespread attention in the last decade, due to the significant improvements in their hydraulic performance, their potentially high application efficiency, and their limited installation costs. However, even if hydraulic design procedures for conventional microirrigation systems are fairly well established, there is still the need to know how different pipe-wall thicknesses of lay-flat pipes can affect the pipe geometry under different operating pressures as well as the related consequences on friction losses. This paper, after comparing two different procedures (caliper and photographic) to asses…
Comment on “Overland runoff erosion dynamics on steep slopes with forages under field simulated rainfall and inflow by C. Li and C. Pan”
2020
Managing sloping landscapes to control soil erosion processes due to rainfall and runoff is a relevant problem, especially when the vegetation is absent or sparse. The aim of this paper was to investigate the applicability of a theoretically resistance law for overland flow under simulated rainfall, based on a power-velocity profile, using field measurements carried out by Li and Pan for three plots with planted forage species (Astragalus adsurgens, Medicago sativa and Cosmos bipinnatus).The relationship between the velocity profile parameter Γ, the flow Froude number and the rain Reynolds number was calibrated using the data by Li and Pan. The obtained overland flow resistance law was also…