ПРИНЦИП НАИМЕНЬШЕГО ДЕЙСТВИЯ В РАСЧЕТЕ ГЛУБИНЫ ВЫХОДНОГО СЕЧЕНИЯ ВОДОСЛИВА С ШИРОКИМ ПОРОГОМ

Abstract

Purpose: development and experimental verification of a method for determining the flow depth in the outlet section of a broad-crested weir, based on the use of the variational principle of least action. Materials and methods. To develop a calculation method, the previously obtained dependences to determine the flow depth in the outlet section of a horizontal canal with a flow moving in a subcritical mode, and a method for determining the flow depth at the crest of a broad-crested weir were used. The theory was tested using a laboratory experiment and computer simulation in the ANSYS 17.0 software package. Results. The comparison of the results of experiments and computer simulation showed the conformance of the calculation results by the method based on the least action principle. The verification was carried out using the Fisher criterion, the criterion value according to the experimental data is 14.35, the criterion tabular value is 19.45, which indicates the adequacy of the proposed method to the experimental data. Conclusions. Based on the direct variational principle of least action, taking into account the influence of centrifugal forces in the flow, a calculation method that makes it possible to determine the outlet section depth of the broad-crested weir has been obtained. The resulting depth also corresponds to the transitional regime, in which the flooded regime changes to the non-flooded one, and in which the type of pool junction changes from surface to bottom one. The comparison showed a discrepancy of 0.4 % with data from outside authors. Experiments with the formation of a stuck jet in the outlet section of the weir showed that the depth in this case does not correspond to the proposed calculation method, this principle is also not implemented when the weir is flooded.