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EXPERIMENTAL STUDY OF APPLICATION OF SOFT SHELLS FOR ENSURING SAFE OPERATION OF HYDROSYSTEM TAILRACES

Y. Kuznetsova, A. Pozdeev, E. Rubacova
Wednesday 19 December 2018 by Libadmin2018

ABSTRACT

We studied the reasons of the formation of local scours in the Cheboksary hydrosystem tailrace on the Volga river. To determine the parameters of the scour basin, we calculated the spatial conjugation of the races in MathCad application software environment. The morphological analysis of soft shells allowed us to establish characteristics of mobile baffles required for protection of the hydrosystem tailraces from scouring. For the formation of an induced vortex flow directed opposite to the channel flow, we proposed a vortex gallery that has an open cylindrical shape with a normal flow axis. The calculation of the platform of the movable base of the vortex gallery with a ballasting tipping roller was performed in MathCad. Parameters of the soft structures for ensuring the safe operation of the hydrosystems calculated in MathСаd were confirmed by experimental studies on a model of the Cheboksary hydrosystem spillway dam. As a result of the experiments on the model at a scale of 1:100 in the hydraulic flume using a multichannel thermoanemometer, we drew diagrams of longitudinal velocities at different flow rates and depths in the transverse flow. The values of temperature equivalents according to thermoanemometers were processed using tables and built-in statistical functions of Excel. The values of dispersion, confidence probability, and Student’s test were obtained. After the measurements, the regression equations were obtained; before the selection of these equations, the reproducibility of data was checked according to Cochrane. The correlation coefficient and the calculated characteristics show the good convergence of the measurement results and the theoretical model. It is proved that the model is adequate and describes the process under study with a confidence probability of 95%. The analysis of velocity diagrams and their comparison allowed to draw a conclusion about the efficiency of the vortex gallery based on soft shells.

Keywords: hydrosystem, spillway dam, tailrace, riverbed scour, vortex gallery, soft shell, safe operation, experiment, multichannel thermoanemometer, temperature equivalent, velocity diagram, Student’s test, reproducibility, dispersion, confidence probability.


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