Validation of transport and friction formulae for upper plane bed by experiments in rectangular pipe

Abstract

Abstract:The paper describes results of validation of authors' recently proposed formulae for sediment transport and bed friction in the upper plane bed regime using laboratory experiments in a pressurized pipe. Flows of mixture of water and fine to medium ballotini (d 50 = 0.18 mm) were observed in a rectangular pipe (51 x 51 mm) with a deposit at the bottom of the pipe. A comparison of test results with transport-formula predictions shows a satisfactory match confirming a good prediction ability of the proposed transport formula at high bed shear. A prediction ability of the friction formulae appears to be less convincing but still reasonable. A joint use of the formulae for transport and friction predicts the delivered concentration of transported sediment within the accuracy range of ± 40 per cent for flows in which transported sediments strongly affect the bed friction, i.e. for flows with delivered concentration of sediment higher than say 3 per cent.

Experimental investigation of internal structure of open-channel flow with intense transport of sediment

“…The first laboratory experiment with layered flow at high bed shear was conducted in a pressurized pipe (Wilson, 1966), and so far a majority of experimental data sets have been collected in laboratory pipes (Matoušek, 2009;Matoušek, 2011;Matoušek et al, 2013;Nnadi and Wilson, 1992;Pugh and Wilson, 1999;Sumer et al, 1996). In pressurized pipes, it is easy to establish the steep slope of the energy grade line required to produce the high bed shear condition required at the top of the stationary deposit.…”

One-dimensional velocity profiles in open-channel flow with intense transport of coarse sediment

“…(1), Ȝ b = bed friction coefficient, u b * = shear velocity associated with channel bed, U = average velocity in the cross section of flow above bed, B r = integration constant (for open channel B r =11.1), R b = hydraulic radius associated with bed and k s = bed roughness. In this law, an evaluation of the bed roughness seems to be different for the so-called weak-transport condition (characterized by a certain threshold value of the Shields parameter) and the intense transport condition [4][5]. For the intense-transport condition, the roughness depends on the Shields parameter and hence a solution for the friction coefficient is implicit which leads to computation failures in some cases.…”

“…So far, research results and publications on this subject are limited and understanding of the processes insufficient. A majority of the work has been done for pressurized flows in enclosed profiles [1][2][3][4][5][6][7]. Examples of experimental and analytical works for intense transport of sediment in open channels are [8][9][10][11].…”

Intense sediment transport: Collisional to turbulent suspension

“…Regime map for the sediment transport of glass spheres in water at mild slopes. Also shown are the experimental points of Matoušek et al 47 (circles), Matoušek 50 (squares), and Pugh and Wilson 44 (triangles).…”

“…RESULTS Figure 2 shows the particle flow rate q as a function of the Shields parameter as predicted by the present theory and measured in the experiments of Matoušek et al 47 The experiments were performed with glass spheres of diameter equal to 0.18 mm and water (R = 5.8; σ = 2.45; w = 0.55) flowing in a rectangular pressurized conduit of height equal to 284 particle diameters. We take the shear stress to be zero at the centerline of the conduit, so that Y = 142 particle diameters.…”