Experience of employment of computational models for water quality modelling

Abstract

The purpose of the article is to develop the required and sufficient conditions under which numerical methods can be used for engineering calculations and for scientific research of hydrodynamic processes in solving practical problems related to predicting the spread of pollutants in water bodies and streams. The conducted studies consisted in comparing the results of laboratory experiments and mathematical modelling, in particular the distribution of heat in a stream with different temperature in water layers was studied. To check the adequacy of the proposed numerical models, calculations were performed and comparisons were made with the results of experimental data. The obtained results allowed to determine the boundaries of the qualitative difference in the flow behaviour for different numbers of Froude and Reynolds. The accuracy of the method was also studied. A number of additional requirements for numerical models were proposed in addition to approcsimation and stability, such as requirements of conservativeness (divergence), existence of trivial solutions on grids, possibility to calculate highly unsteady, quasi-stable, pulsating and stationary flows, requirement of invariance of linearized equations, as well as the requirement of a one-dimensional scheme to be a consequence of a two-dimensional scheme. Distribution of velocities of wind currents using a three-dimensional and two-dimensional model was studied for a real object. A shallow-water bay of the Aral Sea was chosen as the object for the research. Comparison of the calculation results for both models showed that the flow velocity fields, as well as the distribution of pollutants in shallow waters, can be performed using a two-dimensional model.

Regulation of the flow in the area of the damless water intake

“…In earlier works, it was noted that when numerical modeling of flows in such channels using full hydrodynamic equations of water flow motion, taking into account the convective terms, a whirlpool zone appears behind the ledge, which is observed both in physical experiments and in natural conditions; if we use simplified equations with discarded convective terms, the flow spreads immediately behind the ledge, without forming a whirlpool [4]. Note that this paper does not note the impossibility of realizing the hydraulic phenomena described by the Saint-Venant equations without taking into account the friction between the jets in terms of the stationary whirlpool zone corresponding to the Kartvelishvili theorem [5].…”

“…To carry out this work, it is necessary to study a two-dimensional flow in open channels. The most convenient, cheap and multivariate is the method of numerical research [1,2,4,[8][9][10][11]. A detailed comparison of the results of numerical and laboratory modeling of the flow in open channels with a sharp increase in the channel width characteristic of the movement of a water flow behind blind dams was carried out in [16][17][18][19][20].…”

Coastal and deep deformations of the riverbed in the area of a damless water intake

“…Depending on the water content of the year, a stream with a turbidity of up to 5 kg/m3 enters the inlet part of the canal annually. Annual sediment volumes ranged from 7 to 14 million tons [4][5][6]. Due to the existing engineering problems, the above complex is chosen as the object of research of this work.…”

“…In the course of the Amudarya River, the largest head structures with a damless water intake have been built. These include the head structures: the Amuzang, Jaihun, Karakum, Karshi Main and Amu-Bukhara machine canals [4][5][6][7][8][9]. When water is taken from the river, there is a quantitative and qualitative change in the flow characteristics.…”

Flow calculations in intake structures of hydropower plants

“…Scientific research on intake structures is carried out in the fundamental research of the authors to study the problems of improving the theory of unsteady water movement in the "channel -pumping station" system to improve their interconnections [1][2][3][4]. It is the investigation of the laws of change in the kinematic characteristics of the flow in the intake structures of large pumping stations, mainly of the chamber and block type, and assessing the influence of the design of the intake structures on the hydraulic conditions for supplying water to the pumps, in particular, extreme ones, and on the operational parameters of the pumps during unsteady processes [8][9][10][11][12][13][14][15][16][17][18].…”