ASSESSMENT OF SCOUR IN HYDRO SYSTEM TAILRACE USING METHODS OF TECHNICAL DIAGNOSIS AND PRODUCTION FUNCTIONS
Parameters of local scours in an unprotected part of the riverbed behind the hydro system end structures are determined by distribution of kinematic characteristics of the flow. The paper is based on the proposition of the relationship between the scouring effect of the flow and its vorticity degree, due to which the intense shear stresses and upflows that raise soil particles occur in the bottom area. The authors based their research on the hypothesis of N.I. Makkaveev who represented the flow structure as a series of whirlpools. The hypothesis was supplemented with the authors' model of the formation of circulating flows ascending from the bottom and induced by U. Kelvin's vortices. The authors focus on the relationship between the velocity field in the vortex and the pressure force exerted on a soil particle at the boundary of the vortex field. In order to analyze the factors that affect scours in the tailrace of the spillway dam, the authors used the data from laboratory modeling in a hydraulic flume. For the statistical estimate of the significance of the factors affecting the scours, the Bayes method was applied. For this purpose, we distinguished the scour depth levels that determine a value of the statistical diagnosis. Gate opening ratings and relative headrace levels were determined as two groups of diagnostic features. As a result, conditional probabilities of scour diagnoses were calculated using the Bayes method and the specified diagnostic features. The estimate of the impact of the diagnostic features of scour was supplemented with the analysis of limiting differential indicators in the form of production functions. In order to improve the estimate, a preliminary logarithmation of influencing factors and a response function was carried out. Then a multiple least squares regression was performed in MathCad. The authors determined limiting differential efficiencies, characteristics of their substitution, elasticity of production functions, intensity of resource development, and isoquant figures. The authors have comparatively analyzed the factors affecting scours using the Bayes method and the limiting differential indicators. The obtained research outcomes can be used to model the water dispersion and scouring processes in hydro system tailraces