О моделировании гидродинамического режима течений в системах речных русел в период прохождения волны половодья на примере участка р. Оби

Abstract

Рассмотрен пример численного моделирования прохождения волны половодья на участке верхней и средней Оби ниже плотины Новосибирской ГЭС. Расчеты выполнены с использованием численной модели для описания распространения и трансформации волн половодий и паводков в системе русел (STREAM), разрабо танной в ИВЭП СО РАН. Модель основана на одномерных уравнениях Сен-Венана. Система русел моделируется в виде графа типа дерево, в вершинах которого за даются условия сопряжения основных гидродинамических параметров. Приведена приближенная численная оценка порядка точности метода решения. Результаты моделирования хорошо согласуются c данными наблюдений. The goal of the study is to analyze the possibility of using the numerical model STREAM for performing research on the passage of a flood wave in a system of channels. The model was developed at IWEP SB RAS on the basis of one-dimensional Saint-Venant equations. It allows describing the flow regimes in channels, represented as a directed graph of the tree type. In the nodes of the graph (channel gates), the conjugation conditions for the main hydrodynamic parameters flow rates and water levels are set. The finite difference method is used to solve the system of equations. The difference scheme has a second order of accuracy in space and a first order in time. An approximate numerical estimate of the order of accuracy of the model using the Runge method is obtained. Numerical simulation of the Ob river section under the conditions of a high-water year 2014 has been carried out. To construct the morphometric model of the graph, data from the pilot map of the river and data of the expedition studies of IWEP SB RAS were used. The hydrological information is taken from the open access source “Automated information System of State monitoring of water bodies”. As a simulated object, a section of the Ob river from the Novosibirsk hydroelectric power station to Alexandrovskoye village is taken. The length of the site is 1210 km. The flow rates of six tributaries are taken into account. The graph consists of 12 segments. In the closing section, a boundary condition is set for water flow in the form of a flow rate versus level. To estimate the influence of the boundary condition on the simulation results, two water flow curves were constructed according to the data of 2013 and 2014 years. Qualitative and quantitative estimates of the difference in levels using two different curves, as well as comparison with the measurement data, were obtained. It is shown that the calculation method provides an acceptable agreement between the calculated values of water levels and the observational data. The possibility of using the water flow curve according to the data of the previous year as a boundary condition in the closing gate is demonstrated.