Experimental studies of horizontal flow effects in the presence of cavitation on erosion – free dampers

Over the last hundred years, shaft spillways have become widely used in hydraulic engineering practice due to their undeniable advantages: high discharge capacity, maximal water consumption per one cubic meter of concrete, point structure compactness. The modern theory of hydraulic calculations was formed based on works on the study of the operation of a circular spillway with a sharp edge carried out by Wagner in 1954. Although numerous hydraulic studies have not proved many of the statements Wagner's calculation methodology was based on, the materials of his studies have been presented in special hydraulic literature for hydraulic calculations up to date. The accepted design conditions of the drainage surface of the spillway shaft, which is round-cylindrical in the cross-section and in the form of a convex parabolic line in the longitudinal section, do not correspond to the possibilities of work. As a result, the drainage surface is replaced by a system of truncated cones, the joints of which cause flow separation from the drainage surface and the formation of vacuum zones. It results in approximate hydraulic calculations. To eliminate these disadvantages of hydraulic calculations and bring design developments in line with technological possibilities of works, it is possible to replace a round-cylindrical cross-section of the inner surface of the shaft with a polygonal one. In this case, the drainage surface will consist of a system of longitudinal wedges with one-dimensional curvature, for which the formwork can be made of flat sheets. This paper presents materials on the calculation and design of a shaft spillway of a hydroelectric complex with a dodecagonal cross-section for Algeria, and four shafts with an octagonal cross-section and two shafts with a tetragonal cross-section for Syria. The receiving hopper head is round-cylindrical, and the drainage surface is elliptical, which allows adapting the drainage surface to any initial design parameters of shaft spillways.

show abstract

“…The research results and recommendations of P.P. Mois are given only in the textbooks of L. N. Rasskazov [9,10], [18][19][20][21][22].…”

Section: Methodsmentioning

confidence: 99%

Improvement of the theory of shaft spillway calculations

et al. 2021

View full text Add to dashboard Cite

show abstract

“…To reproduce cavitation and study its effect on the elements of hydraulic structures, cavitation units are used. According to the principle of their operation, these installations can be subdivided into several groups: acoustic rotary and magnetostrictive installations, jet-impact vacuum stands, hydrodynamic tubes [22,23]. In hydraulic engineering, hydrodynamic tubes and vacuum benches are mainly used.…”

Section: Vacuum Unit Models and Similarity Criteriamentioning

confidence: 99%

Force effects of the flow on energy absorbers in the presence of cavitation

et al. 2021

View full text Add to dashboard Cite

As the experience of operating high-pressure spillway structures shows, the operating conditions of the downstream extinguishing devices are very difficult. At flow rates, more than 12–15 m/s, downstream damping devices, as a rule, operate in a cavitation mode. First of all, this mode of operation gives rise to erosional destruction of the damper itself and the waters near it. This occurs where the cavitation torch closes on the structure. Attempts to avoid these desirable phenomena by lining erosion sites with steel sheets do not always lead to the desired result since it is not uncommon for the steel lining to be torn off by hydrodynamic forces. The separation of the cladding occurs in two cases: firstly, when the cladding is not in close contact with the concrete to be protected, and secondly, its anchoring is not enough. In both cases, fracture occurs from fatigue phenomena in the metal due to multiple oscillatory cycles from hydrodynamic loads. It is difficult to avoid this in cavitation modes since the spectrum of pressure pulsations, in this case, is very wide, which leads to oscillations of linings at resonant frequencies. Apparently, the strength of the linings is an object of special research, and in the future, it should be dealt with theoretically and experimentally. Hydrodynamic forces at high flow rates in the zone of intense energy extinguishing can reach such values that they can lift and overturn concrete slabs of water walls and water walls. Currently, there are practically no specific and accounting for vertical hydrodynamic loads on slabs of water walls in the presence of cavitation on erosion-free absorbers in the technical literature. To a certain degree of approximation, it is possible to use experimental data obtained on a model of the same structure but operating without cavitation, as data on hydrodynamic loads in the downstream of structures operating in a cavitation mode. The main disadvantage of such comparisons is that there is no guarantee that the amplitude and frequency characteristics of the flow during cavitation do not change (in particular, the amplitudes do not increase) as the cavitation limit is approached.

show abstract

“…The research was carried out at the vacuum bench of the laboratory of hydraulic structures of the MGMI. [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32].…”

Section: Experimental Technique Vacuum Unit Models and Similarity Criteriamentioning

confidence: 99%

Experimental study of horizontal effects of flow on non-erosion absorbers in the presence of cavitation

et al. 2021

View full text Add to dashboard Cite

This article is devoted to one relatively small issue of the dynamics of hydraulic structures, the determination of horizontal hydrodynamic loads on energy absorbers of a high-pressure catchment area in a cavitating flow in the presence of erosion-free absorbers. In connection with the intensive construction of high and medium-pressure hydroelectric systems, spillways that operate at high flow rates, a very urgent task is to develop reliable and economical downstream devices that provide intensive damping of flow energy in a stilling well with favorable uninterrupted flow regimes and the absence of cavitation erosion of streamlined elements. Traditional methods of extinguishing energy using stilling wells and walls do not always solve the problem. In several cases, additional elements such as energy absorbers are installed, which effectively deal with malfunctioning currents. However, most of the used types of absorbers have a serious drawback - they are destroyed during cavitation studies by prof. N.P. Rozanov and his students made it possible, based on experiments, to develop several types of erosion-free or close to erosion-free dampers and obtain a dependence to determine the hydrodynamic loads acting on them at various stages of cavitation. This made it possible to use energy absorbers at high flow rates, which was done at the spillways of the Shamkhor and Artyomovsk hydroelectric power plants.

show abstract

Experimental studies of horizontal flow effects in the presence of cavitation on erosion – free dampers

Cited by 33 publications

References 4 publications

Improvement of the theory of shaft spillway calculations

Improvement of the theory of shaft spillway calculations

Force effects of the flow on energy absorbers in the presence of cavitation

Experimental study of horizontal effects of flow on non-erosion absorbers in the presence of cavitation

Contact Info

Product

Resources

About