Search results for "Gravel bed"

Incomplete self-similarity and flow velocity in gravel bed channels

2000

Velocity measurements, previously carried out using both a miniature current flowmeter and an acoustic Doppler velocimeter, are used to verify the applicability of the incomplete self-similarity theory to deduce the velocity profile in a gravel bed channel. Then, for the velocity profiles having the maximum value below the free surface and for the S-shaped profiles, the power velocity distribution is corrected using a new divergence function. For each value of the depth sediment ratio the nondimensional friction factor parameter is calculated by integration of the measured velocity distributions in the different verticals of the cross section. Finally, a semilogarithmic flow resistance equa…

Assessing flow resistance in gravel bed channels by dimensional analysis and self-similarity

2018

Abstract In this paper a new flow resistance equation for open channel flow, based on the integration of a power velocity profile, was tested for gravel bed channels. First this flow resistance equation, theoretically deduced by dimensional analysis and incomplete self-similarity condition, was reported. Then a relationship between the Γ function of the velocity profile, the channel slope and the Froude number was calibrated by the available laboratory measurements of flow velocity, water depth and bed slope carried out in 416 flume experimental runs with a gravel bed. Then the relationship for estimating Γ function and the theoretical resistance equation was tested by 83 independent flume …

Experimental study of boulder concentration effect on flow resistance in gravel bed channels

2021

Abstract Previous studies demonstrated that for open channel flows the power velocity profile can be integrated to obtain the flow resistance law. In this paper the relationship between Γ coefficient of the power velocity distribution, the channel slope and Froude number (Eq. (9) ) is firstly presented. Then the measurements carried out in a laboratory flume covered by hemispheric elements for two different hydraulic conditions (partially inundated and inundated) are used to calibrate this relationship. These elements are placed with a square arrangement and have a concentration range 4–64%. For the two investigated hydraulic conditions, this analysis demonstrates that the relationship to e…

ADV measurements of velocity distributions in a gravel-bed flume

2003

Velocity measurements carried out by an acoustic doppler velocimeter (ADV) in a rectangular laboratory flume having a gravel bed are presented. The velocity profiles are measured in six verticals of the channel cross-section having an increasing distance (from 4 to 38.5 cm) from the flume wall. The experimental runs are carried out for five different bed arrangements, characterized by different concentrations of coarser elements, and for the two conditions of small- and large-scale roughness. For both hydraulic conditions, the velocity measurements are first used to test the applicability of the Dean profile and of the logarithmic profile corrected by a divergence function proposed in this …

Assessing theoretical flow velocity profile and resistance in gravel bed rivers by field measurements

2018

Previous studies showed that integrating a power velocity profile, deduced applying dimensional analysis and the incomplete self-similarity condition, the flow resistance equation for open channel flow can be obtained. At first, in this paper the relationship between the Gamma function of the power velocity profile, the channel slope and the Froude number, which was already empirically introduced in a previous paper, is now theoretically deduced. Then this relationship is calibrated using the field measurements of flow velocity, water depth and bed slope carried out in 101 reaches of gravel bed rivers available by literature. The proposed relationship for estimating Gamma function and the t…

Closure to "Analyzing turbulence intensity in gravel bed channel"

2008

Closure to "Applying hypothesis of self-similarity for flow-resistance law in calabrian gravel-bed rivers" by Vito Ferro and Paolo Porto

2019

This Closure is a paper in which the Authors answer to the queries of a Discusser.

Influence of bed roughness on flow and turbulence structure around a partially-buried, isolated freshwater mussel

2023

The present study uses eddy-resolving numerical simulations to investigate how bed roughness affects flow and turbulence structure around an isolated, partially-buried mussel (Unio elongatulus) aligned with the incoming flow. The rough-bed simulations resolve the flow past the exposed part of a gravel bed, whose surface is obtained from a laboratory experiment that also provides some additional data for validation of the numerical model. Results are also discussed for the limiting case of a horizontal smooth bed. Additionally, the effects of varying the level of burial of the mussel inside the substrate and the discharge through the two mussel siphons are investigated via a set of simulatio…

Effects of Boulder Arrangement on Flow Resistance Due to Macro-Scale Bed Roughness

2023

Flow resistance in gravel-bed channels is not only affected by the shape and size of the roughness elements, but also by their arrangement on the channel bed surface (position to flow streamlines, spacing between elements, and their protrusion from the channel bed). Many investigations proved that open channel flow resistance can be obtained by integrating the power velocity profile. For a macro-scale roughness condition, this study aims to investigate the effect of different boulder arrangements on flow resistance. First, for each arrangement, the equation relating Γ function of the power velocity profile, the Froude number, and the channel slope was calibrated using available measur…

Discussion on 'Estimating depth-averaged velocities in rough channels'

2002

In this short communication the four estimate criteria of the depth-averaged local velocity proposed by Byrd et al. (Earth Surface Processes and Landforms, 2000, Vol. 25, pp. 167-173) are compared both with the three-point method of Bathurst and with the average velocity obtained by integrating the velocity profile (FPa2) suggested by Ferro and Pecoraro (Water Resources Research, 2000, vol. 36, pp. 2761-2770). The comparison was carried out using 84 velocity profiles measured by an acoustic Doppler velocimeter in a rectangular flume with a gravel bed. Copyright © 2002 John Wiley and Sons, Ltd.