The article reveals the fundamentals of engineering and designing mobile weir with rectangular opening for farmlands, applicable for measuring discharge in interfarm and temporary canals. It includes the fundamentals of choosing most efficient structural solutions for the weir, choosing material for fabrication of its main elements, performing the static design for weir horizontal beams according to marginal states of providing reliability and stability of weir main elements. Results of calculations of diameter of steel bar for rectangular weir with B=25cm showed that the diameter needed is 6mm. The diameter is small enough for the weir to be called a thin plate weir. Thus, using 6mm bar is reasonable enough from the point of view of stability and the by the requirements for a thin plate weir.

Great attention around the world is paid to the design and construction of riverbank protection and channel control structures on submountain section of rivers. High slopes (i=0,001÷0,004 and higher), flow kinetics and ability to transport large amount of sediments are the features of submountain section of rivers. Most of the research in this sphere has been conducted on the study of patterns of flow constrained by transverse structures in valley parts of rivers. The main goal of this work is to establish the physical picture of flow around a combined dam in submountian river, the through-flow part of which is made of tetrahedrons, as well as to develop a design method for flow velocity field. Formations of two regimes have been established experimentally, i.e. “calm” at ia<icr and “critical” at ia≥icr. These regimes are mainly affected by flow contraction degree na, and Froude number Fr. The presence of the following zones was established: core, intensive turbulent mixing and backflow zones, as well as the affinity of velocity fields in the zone of mixing by Shlihting-Abramovich. Prandtl has realized the task for “calm” regime with the use of integral relationship expressing law of conservation of momentum in the flow, equation for conservation of discharge and differential equation for nonuniform motion of transit flow with the account of tangential turbulent stresses on lateral surfaces. As opposed to the existing solutions, we accounted for the presence of two regions of spreading with different slopes of water surface, horizontal component of fluid weight, nonuniform distribution of velocities in head section, high roughness and the case when sections of target and vertical contraction do not match. Satisfactory results were obtained by comparing theoretical solution and experimental data.

The design of the track to control river channel directing flow to water intake point requires the solution of a number of issues. Including the magnitude of the deflection of the dynamic axes of flow contracted by control structures. The main goal of the work is to develop the design method for the deflection of the dynamic axes of flow unilaterally contracted by a combined dam with a through-flow part made of tetrahedrons. The task is accomplished using Varignon’s theorem and the equation of conservation of discharges written for sections where flow natural condition is maintained in the headrace and contracted section. The concept of flow around the coefficient is introduced as the ratio of incoming discharge to the discharge passing the through-flow part of the combined dam. Design relationships have been proposed to determine the relative deflection of the dynamic axes of flow specific discharge in the non-contracted section of flow carrying capacity of the through-flow part is evaluated through the coefficient of flow-around. Numerical methods carried out for Chirchik river conditions have shown satisfactory results.

Every major river in the world consists of mountainous, foothills, and flat areas characterized by different flow regimes. The foothill areas differ in slopes i = 0.001 ÷ 0.004, flow kinetics Fr > 0.15, and the size of sediments. The riverbed is unstable, and the banks are prone to erosion. The construction of coastal protection structures requires solving complex issues related to their design. The analysis showed that most of the studies, including ours, were carried out for the conditions of lowland rivers. This work aims to establish the flow features of the foothill sections of a combined dam with a through part of tetrahedra when the ratio of the through part ℓs to the total length of the dam ℓd is greater than or equal to 0.5, i.e., ℓs/ℓd. ≥ 0.5 The presence of a satellite flow behind the through part, a weakly perturbed core, and the presence of two zones of intense turbulent mixing was experimentally established, and the universality of the velocity distribution, which obeys the theoretical dependence of Schlichting-Abramovich, was confirmed. It is once again confirmed that the dependence is on the slope of the bottom, the Froude number, the degree of constraint, and the formation of "calm" and "critical" flow modes. The nature of the level changes along the length of the compression region in the core, and the satellite flow differ from each other, and the alignments occur in the vertical compression alignment. The problem is implemented for the "calm" mode using an integral relation characterizing the law of conservation of momentum in the flow, the equation of conservation of flow, and the differential equation of uneven motion recorded for the satellite flow behind the through part of the combined dam. The presence of a satellite flow, two zones of intense turbulent mixing, and the different nature of the leveled regime of the main and satellite flows are taken into account. A comparison of theoretical solutions with experimental ones shows their similarity.

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.