10 research outputs found
Probabilistic Modelling in Solving Analytical Problems of System Engineering
This chapter provides some aspects to probabilistic modelling in solving analytical problems of system engineering. The historically developed system of the formation of scientific bases of engineering calculations of characteristics of strength, stability, durability, reliability, survivability and safety is considered. The features of deterministic and probabilistic problems of evaluation of the characteristics of strength, stiffness, steadiness, durability and survivability are considered. Probabilistic problems of reliability, security, safety and risk assessment of engineering systems are formulated. Theoretical bases and methods of probabilistic modelling of engineering systems are stated. The main directions of solving the problems of ensuring security and safety according to the accident risk criteria are determined. The possibilities of probabilistic modelling methods in solving the problems of strength, reliability and safety of engineering systems are shown in practical examples
Laboratory, Bench, and Full-Scale Researches of Strength, Reliability, and Safety of High-Power Hydro Turbines
Large hydropower plants (HPPs) are categorized as critically and strategically important infrastructure facilities in industrialized countries. Therefore, the issues of ensuring HPPs safety are of paramount importance. In this chapter, the basic aspects of the safety analysis of HPPs, calculation and experimental substantiation of the strength, and resource and reliability of the main equipment are discussed. The scientific and technical measures to ensure safety of HPPs are presented. As a defining measure of safety, it is proposed to ensure the protection of HPPs from severe accidents and disasters according to risk criteria. The main provisions of the risk assessment are presented on the basis of a sequential analysis of loads, features of stress-strain states, characteristics of mechanical properties, and limit states of hydraulic equipment of HPPs. The issues of calculation and experimental evaluation of hydro turbine’s resource, which limit the safety of HPPs, are considered. The features of technical diagnosis of hydraulic turbines are considered; characteristic defects and damages are described. The main provisions of the estimated residual life of hydro turbines are presented. The results of the risk estimates of HPPs and hydro turbine resource are given
Numerical modeling of a dilution and transport of highly salty effluent in water bodies
The paper focuses on modeling of dilution
and transport of highly salty effluent in water bodies. The modeling is made for
three-dimensional unsteady regimes of turbulent mixing in the conditions of strong
density stratification. Numerical results allow to determine the limits of applicability
of two-dimensional hydrodynamic models and to estimate the maximal possible
environmentally safe volumes of highly salty effluent disposal
A Numerical Study of the Influence of Channel-Scale Secondary Circulation on Mixing Processes Downstream of River Junctions
International audienceA rapid downstream weakening of the processes that drive the intensity of transverse mixing at the confluence of large rivers has been identified in the literature and attributed to the progressive reduction in channel scale secondary circulation and shear-driven mixing with distance downstream from the junction. These processes are investigated in this paper using a three-dimensional computation of the Reynolds averaged Navier Stokes equations combined with a Reynolds stress turbulence model for the confluence of the Kama and Vishera rivers in the Russian Urals. Simulations were carried out for three different configurations: an idealized planform with a rectangular cross-section (R), the natural planform with a rectangular cross-section (P), and the natural planform with the measured bathymetry (N), each one for three different discharge ratios. Results show that in the idealized configuration (R), the initial vortices that form due to channel-scale pressure gradients decline rapidly with distance downstream. Mixing is slow and incomplete at more than 10 multiples of channel width downstream from the junction corner. However, when the natural planform and bathymetry are introduced (N), rates of mixing increase dramatically at the junction corner and are maintained with distance downstream. Comparison with the P case suggests that it is the bathymetry that drives the most rapid mixing and notably when the discharge ratio is such that a single channel-scale vortex develops aided by curvature in the post junction channel. This effect is strongest when the discharge of the tributary that has the same direction of curvature as the post junction channel is greatest. A comprehensive set of field data are required to test this conclusion. If it holds, theoretical models of mixing processes in rivers will need to take into account the effects of bathymetry upon the interaction between river discharge ratio, secondary circulation development, and mixing rates
ECOLOGICAL-HYDROLOGICAL ASPECTS IN FORECASTING OF CONSEQUENCES AND STANDARDIZATION OF SEWAGE DISPOSAL INTO AQUEOUS OBJECTS
The aim is to create the system for forecasting of the abiotic consequences and standardization of the technogenic loads connected with sewage disposal into the aqueous objects. The analysis of the methods describing the behaviour of both the conservative and heterophase non-conservative pollutants in the aqueous objects has been given. The criteria of their optimal choice depending on the aqueous object character, sewage disposal condition, pollutant type, design region dimension, volume and accuracy of giving initial information have been proposed. The migration has been investigated, and the methods describing the dynamics of the heterophase non-conservative pollutants have been proposed. The necessity of the introduction has been proved, and the methodology of determining maximal ecological-permissible concentration on base of the analysis of the statistics of their background content for the pollutants which are characteristics for natural condition of the aqueous objects and also on a level with traditional system of the local limitations the integral limitations of the power in the technogenic flows for large aqueous objects on base of comparison with natural flows evaluated on a whole on the aqueous object has been proposed. The developed system for operative forecasting and standardization of the technogenic loads on the aqueous objects has been introduced in the Perm Regional Committee on the Nature Protection.Available from VNTIC / VNTIC - Scientific & Technical Information Centre of RussiaSIGLERURussian Federatio
Defects Assessment in Subsea Pipelines by Risk Criteria
Subsea inter-field pipelines are an important element of offshore oil and gas infrastructure. Leakage or fracture of these pipelines is associated with the risk of large economic and environmental losses. One of the main sources of pipeline fracture is pipe defects. The presented section discusses the methodological aspects of assessing the hazard of defects of subsea inter-field pipelines by risk criteria of accidents. A conceptual approach of defects hazard assessing by risk criteria has been formulated, based on analysis the requirement of modern standards. The risk is defined as the probability of negative consequences, the scale of which is determined by the hazard class of pipeline accidents. The probability and scale of accidents are linked by a risk matrix. A method for a three-level assessment of the suitability of a pipeline for operation after in-line inspection has been developed. The method allows assessing the hazard of the most typical defects in subsea pipelines, such as metal loss, metal delamination, cracks and crack-like defects. The allowable defect sizes are determined for the given risk criteria using partial safety factors. The novelty of the methodology lies in the substantiation of safety factors according to risk criteria corresponding to a given class of damage and loss. A scheme for making decisions on the admissibility of defects by risk criteria has been developed. An example of hazard assessment of defects in subsea pipelines is presented
The Influence of Intra-Day Non-Uniformity of Operation of Large Hydroelectric Powerplants on the Performance Stability of Water Intakes Located in Their Upper Pools
The creation of reservoirs in water streams leads to significant changes in the hydrological regime of water bodies: it allows smoothing the peaks of maximum water discharge during a flood period and regulating low-water flow. The creation of reservoirs with significant storage capacity makes it possible to solve a wide range of water-management problems, including the use of falling water energy for hydropower purposes, and maintenance of the uninterrupted water supply and navigation. Since constructed dams are usually operated by hydropower companies, the regulatory regime for the discharge of water into the lower pool is often determined by the daily electricity consumption regime. Intra-day variations in the volume of water discharges through hydroelectric power stations generate multidirectional streams in the upper pool, which can affect the operation of other water withdrawal systems. This paper considers the effect of intraday variations in water discharges into the lower pool on the dynamic and physical properties of the water mass in the region of the location of drinking water-intake heads of Perm city and the quality of the withdrawn water
A numerical study about the influence of channel-scale secondary circulation on mixing processes at Kama/Vishera confluence
International audienceConfluences are common components of all riverine systems, and are characterized by converging flow streamlines and mixing of separate flows, which can take some significant distance to be complete. Whilst turbulent diffusion and Taylor dispersion are expected to affect mixing in any open channel flow, the analysis of mixing at river confluences should also consider some peculiar processes, which could be divided between near-field processes and far-field processes. The former, which have been well studied, are those operating at the junction itself and lead to rapid mixing only if some form of asymmetry (geometry, discordance, momentum, density difference) between the tributaries exists. The latter are advective processes, such as secondary circulation, that can enhance mixing to degrees greater than those associated with turbulent diffusion or Taylor dispersion combined. These processes, which have received less attention, were investigated using a three-dimensional computation of the Reynolds averaged Navier-Stokes equations combined with a Reynolds stress turbulence model for the confluence of the Kama river and Vishera rivers in the Russian Urals. To test the hypothesis that far-field mixing can be both enhanced and reduced by the type of secondary circulation that develops, numerical simulations on an idealized configuration (rectangular channel with no curvature) and on the real configuration with the natural planform and/or bathymetry were carried out to isolate the relative impacts of real planform and bathymetry on secondary circulation and mixing for different combinations of momentum/discharge ratio. Results show that if the rivers are represented as an idealized junction, the initial vortices that form due to channel-scale pressure gradients decline rapidly with distance downstream. Mixing is slow and incomplete at more than 10 multiples of channel width downstream from the junction corner. On the other side, if the real configuration is introduced, rates of mixing increase dramatically. This is related to both increase intensity of secondary circulation at the junction and the formation of a single channel-scale vortex downstream of the junction. The latter appears to be aided by curvature of the post-junction channel. This effect is strongest when the discharge of the tributary that has the same direction of curvature as the post junction channel is greatest.</p><p>The study was performed under financial support of the Government of Perm Krai (grant C 26/788) and Russian Foundation for Basic Research (grant 19-41-590013)
Peculiarities of Hydrodynamics of Small Surface Water Bodies in Zones of Active Technogenesis (on the Example of the Verkhne-Zyryansk Reservoir, Russia)
As a rule, large modern industrial complexes are significant water users. This raises the problem of providing them with reliable and sustainable water supply systems. To solve this problem, relatively small, special reservoirs for technical water supply are often created. When creating them, it is a priori assumed that their water masses will be comparatively homogeneous over the aquatorium and throughout the depths, and so, therefore, that their flushing can be successfully used to prevent a possible accumulation of pollutants. The experience of operating such reservoirs in the Verkhnekamsky potassium and magnesium salt development zone in Ural, Russia, has shown that, due to intense diffuse pollution, the reservoirs are characterized by significant vertical non-uniformity, fundamentally altering the hydrodynamics of these water bodies. Based on a series of research, including field observations and computational experiments, the present paper reveals that the vertical non-uniformity of water masses plays a key role in ensuring the sustainability of technical water supply