Abstract
The areas of the foothill rivers are distinguished by large bottom slopes reaching 0.004, with increased kinetics of the flow of more than 0.15, and by gravel-pebble sediments of the river bed and flow. An analysis of the studies performed on the regulatory structures showed that the bulk of them was performed for the conditions of lowland rivers. In the article, a design of a combined dam with a through part of tetrahedrons is proposed. The experiments were conducted in a flume with a rigid bottom and with a variable slope of. The modeling was performed according to Froude in a self-similar area. Experimental studies revealed the presence of two flow spreading modes depending on the bottom slope: a “calm” mode at iД < iκр and a “critical” mode at iД > iκр These modes are mainly influenced by the degree of constraint and the Froude number. In the previous articles, a solution to the problem was provided for the case iД < iκр, which covers the foothill sections of rivers at a “calm” mode. At a further increase in the degree of flow constraint n > 0.3 and the Froude number Fr > 0.15, a “critical mode” is observed. Here, a solution to the problem for this case is given. The problem, in this case, differs from the previously considered one by non-uniform distribution of velocities in the weakly disturbed core, a significant reduction in the length of the vortex zone; the vertical compression of the flow continues to the end of the vortex zone. The versatility of the velocity distribution in the zones of weakly disturbed core and intense turbulent mixing is experimentally substantiated. With theoretical studies, using the basic equations of applied mechanics, a method for calculating the velocity field was developed, and the planned dimensions of the vortex zones were established. The comparison with experimental data showed satisfactory agreement.
Highlights
Stream-bank erosion brings huge losses worldwide to the economies of countries located in coastal zones
The foothill sections of the rivers have their own features, which consist of the morphology and the hydraulics of the flows. [16, 17]
In the laboratory of Hydrotechnical Engineering of the Institute, new structures were developed, and large-scale studies of the operation of combined dams with a through part of piles driven into the river bottom were carried out [20,21,22,23,24]
Summary
Stream-bank erosion brings huge losses worldwide to the economies of countries located in coastal zones. On the foothill rivers of Uzbekistan (Zarafshan, Chirchik, Kashkadarya, Akhangaran and others), the slopes of the channel vary within i 0.001 0.004 , the kinetics of the flow is Fr 0.15 0.5 Research for these conditions was conducted for blind and through transverse structures [17,18,19]. In the laboratory of Hydrotechnical Engineering of the Institute, new structures were developed, and large-scale studies of the operation of combined dams with a through part of piles driven into the river bottom were carried out [20,21,22,23,24]. Theoretical and experimental studies were carried out in a flume of a variable slope, the physical picture of the flow constrained by a combined dam with a through part of tetrahedrons was revealed, and a method for their calculation was developed
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