Abstract
Water flow in channels with a compound cross-section involves an exchange of water mass and momentum between the slower flowing water in the floodplains and the faster water in the main channel. This process is called the streams interaction. As a result, the water velocity in the main channel decreases, and at the same time the velocity and depth of flow increase in the part of the floodplains adjacent to the main channel. Diversification of the surface roughness of the main channel and floodplains significantly affects the form of interactions. The results of laboratory experiments were used to characterize the influence of interactions on the discharge capacity of the channel with diversified roughness. The reduction in velocity of the main channel caused by the stream interactions is described with the apparent friction coefficients introduced at the boundary between the main channel and the floodplain. The obtained values of resistance coefficients, supplemented with the values from experiments reported in the literature, were used to establish a relationship useful in assessing the discharge capacity of such channels.
Highlights
For the practice, the kinematic structure of the stream in the channel with a compound cross-section can be characterized with sufficient accuracy, as the distribution of the depth averaged velocity in the cross-section
The calculated values of apparent resistance coefficients fa and resistance coefficients of the main channel fm as well as of the bottom fmb, the left side slope of the main channel, fms, the bottom of the left floodplain ffb, of the compound cross section in experiments made in variants W 1.0, W 2.0 and W
The analysis of the values of resistance coefficients determined for the main channel with the compound cross-section
Summary
The kinematic structure of the stream in the channel with a compound cross-section can be characterized with sufficient accuracy, as the distribution of the depth averaged velocity in the cross-section. A review of formulas derived to where: vm —average flow velocity in the main channel, g—gravitational acceleration, fm —resistance describe apparent tangential stresses at the boundary of streams in the main channel and floodplains coefficient for the main channel cross-section, calculated for the wetted perimeter, accounting for can be found in Moreta and Martin-Vide (2010) [14]. The flow resistance coefficients at the division boundary of the compound cross-section, according in the main channel of the compound cross-section, using the Darcy-Weisbach formula: to Nuding (1998) [15], calculated on the basis of apparent shear stresses, depend on the following parameters of the channel (Figure 1): 8gRm So vm =.
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