The paper presents recommendations for using the results obtained in sediment transport simulation and modeling of channel deformations in rivers. This work relates to the issues of empirical modeling of the water flow characteristics in natural riverbeds with a movable bottom (alluvial channels) which are extremely complex. The study shows that in the simulation of sediment transport and calculation of channel deformations in the rivers, it is expedient to use the calculation dependences of Chézy’s coefficient for assessing the roughness of the bottom sediment mixture, or the dependences of the form based on the field investigation data. Three models are most commonly used and based on the original formulas of Meyer-Peter and Müller (1948), Einstein (1950) and van Rijn (1984). This work deals with assessing the hydraulic resistance of the channel and improving the river sediment transport model in a simulation of riverbed transformation on the basis of previous research to verify it based on 296 field measurements on the Central-East European lowland rivers. The performed test calculations show that the modified van Rijn formula gives the best results from all the considered variants.
The results of laboratory modeling of bottom reformations in the area of bridge pier crossing over water barriers are presented. The basics of hydraulic modeling are described taking into account the similarity criteria. The flow around a rectangular box (tongued-and-grooved protection of a constructed pier) is experimentally studied, the pattern of erosion if an ice-cutter device is installed in front of the box in the form of a triangle directed at an acute angle towards the flow is considered. The structure of the bottom relief in the vicinity of the tongued-and-grooved box is experimentally studied under the conditions of the bottom erosion. Two cycles of experiments were performed for different values of the flow depth and specific discharge of water. Localization and quantitative characteristics of washouts and alleviation of sandy soil in the vicinity of the streamlined design are established. It is noted that the main mechanism for the formation of the bottom relief is a horseshoe vortex at the base of the pier. A stagnation zone is formed inside the horseshoe. In the absence of an ice cutter, the main zones of soil erosion occur in the corners of the frontal bezel of the box, alluvium forms in the rear unit of the design. By installing an ice-cutter device in front of the box, the erosion zones move to the vicinity of the corners lying at the base of the triangular ice-cutter facing the box. The alluvium remains in the wake of the box. At the same time, the absolute values of the erosion depth and the height of the alluvium under installing the ice-cutter close to the box are reduced. The data of velocity measurements on the free surface and in the flow thickness are also given.
The results of laboratory modeling of the influence of the bridge crossing supports erected during the construction of the highway near the existing railway bridge on the flow characteristics in the channel of the Neva River are presented. Modeling was carried out for two options for the location of the new bridge supports relative to the existing bridge structures. The limits of changes in the characteristics of the river flow are taken into account - the maximum, minimum and residual flows and benchmarks of the water level in the channel. Studies have shown that the construction of the designed bridge supports in the channel does not cause significant changes in the flow structure. There is a redistribution of the flow rate in the sections of the existing and designed bridges. The average velocities in the navigable span of the existing bridge are somewhat reduced when new supports are built. The velocity diagram is aligned along the width of the central and side spans, and a vortex wake is more clearly formed in the area behind the supports.
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