Institute of Technical Mechanics

Dnipropetrovsk, Ukraine

Institute of Technical Mechanics

Dnipropetrovsk, Ukraine

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Kovalenko Y.,CINVESTAV | Gorev N.B.,Institute of Technical Mechanics | Kodzhespirova I.F.,Institute of Technical Mechanics | Prokhorov E.,CINVESTAV | Trapaga G.,CINVESTAV
Water Resources Management | Year: 2014

This paper analyzes the convergence of a pressure-driven analysis (PDA) model of a water distribution network solver based on Todini's global gradient algorithm. The PDA model is constructed by embedding a pressure-demand relationship in the EPANET simulator code. To avoid spurious convergence, a residual-based convergence error was used. The introduction of pressure-dependent demands is shown to result in a far poorer convergence. The study of solver convergence as a function of the smoothness of the pressure-demand curve has demonstrated that, statistically, a smooth pressure-demand relationship gives a somewhat better convergence. To improve convergence, use was made of a quadratic approximation of the Hazen-Williams head loss-flow relationship in the vicinity of zero and the correct implementation of the Darcy-Weisbach formula in the solver. To further improve convergence, an iteration step control technique called the line search was used. The analysis of solver convergence for different line search variants has shown that the line search in its usual form is not efficient enough and may result in poorer convergence. A necessary error decrease algorithm, whose use in the line search improves solver convergence, is proposed. It is shown that due to the convergence improvement methods the convergence of the PDA solver is somewhat better than that of the demand-driven analysis solver and sufficient for direct problems such as design, for example. © 2014 Springer Science+Business Media Dordrecht.


Gorev N.B.,Institute of Technical Mechanics | Kodzhespirova I.F.,Institute of Technical Mechanics | Prokhorov E.,CINVESTAV
Journal of Hydraulic Engineering | Year: 2010

A procedure for the experimental convergence evaluation of a hydraulic-network solver is proposed, based on using genetic algorithms to search for network parameter values that maximize the number of iterations of the hydraulic-network solver under test. The efficiency of the method is demonstrated by the example of convergence evaluation for the EPANET hydraulic simulator. Examples of a pipe network and of combinations of parameter values for which the static solver of the simulator fails to converge in a reasonable number of iterations are given. The features of the EPANET 2.00.12 solver responsible for loss of convergence are discussed. New criteria for the automatic start of solution damping aimed at improving the convergence of the solver are proposed. The better convergence of the EPANET solver modified in accordance with these criteria is confirmed by the random and the proposed search-based testing method. © 2010 ASCE.


Pylypenko O.V.,Institute of Technical Mechanics | Doronin A.V.,Institute of Technical Mechanics | Gorev N.B.,Institute of Technical Mechanics | Kodzhespirova I.F.,Institute of Technical Mechanics
International Conference on Mathematical Methods in Electromagnetic Theory, MMET | Year: 2014

It is shown that the displacement of a target can be measured by microwave interferometry at an unknown reflection coefficient to reasonable accuracy with the use of as few as two probes. A two-probe displacement measurement technique is presented. © 2014 IEEE.


Zabolotnyy P.,Institute of Technical Mechanics
International Conference on Mathematical Methods in Electromagnetic Theory, MMET | Year: 2014

The eigenfrequencies of a truncated biconical cavity with a dielectric cylinder are calculated as a function of the dielectric permittivity of the cylinder and the cone angles. The results of analytical calculation by the quasiregular approximation method are compared with the numerical results obtained using the classical scheme of the finite-element method. The range of cone angles in which the quasiregular approximation method is applicable is reported. © 2014 IEEE.


Gorev N.B.,Institute of Technical Mechanics | Kodzhespirova I.F.,Institute of Technical Mechanics | Prokhorov E.,CINVESTAV
Water Resources Management | Year: 2011

A method for automatic functional testing of hydraulic simulators is proposed. The method is based on using genetic algorithms to search for network parameter values at which the simulator under test computes solutions that do not satisfy the governing network equations. The search is made by maximizing the residual of the governing equations. The application of the method to the latest version of the EPANET hydraulic simulator demonstrates its efficiency in detecting incorrect results. The results of quantitative assessment of the functional adequacy of the EPANET solver by random testing are presented. The paper provides examples of hydraulic networks and of parameter value combinations for which incorrect results occur. An example of the use of automatic functional testing together with automatic convergence testing in a comprehensive study of the flow control valve model of the EPANET solver is given. © 2011 Springer Science+Business Media B.V.


Gorev N.B.,Institute of Technical Mechanics | Kodzhespirova I.F.,Institute of Technical Mechanics
Water Resources Management | Year: 2013

To analyze water distribution networks under pressure-deficient conditions, most of the available hydraulic simulators, including EPANET 2, must be either modified by embedding pressure-dependent demands in the governing network equations or run repeatedly with successive adjustments made to specific parameters until a sufficient hydraulic consistency is obtained. This paper presents and discusses a simple technique that implements the square root relationship between the nodal demand and the nodal pressure using EPANET 2 tools and allows a water distribution network with pressure-dependent demands to be solved in a single run of the unmodified snapshot hydraulic analysis engine of EPANET 2. In this technique, artificial strings made up of a flow control valve, a pipe with a check valve, and a reservoir are connected to the demand nodes before running the engine, and the pressure-dependent demands are determined as the flows in the strings. The resistance of the artificial pipes is chosen such that the demands are satisfied in full at a desired nodal pressure. The proposed technique shows reasonable convergence as evidenced by its testing on example networks. © 2013 Springer Science+Business Media Dordrecht.


Gorev N.B.,Institute of Technical Mechanics | Kodzhespirov I.F.,Institute of Technical Mechanics | Kovalenko Y.,CINVESTAV | Prokhorov E.,CINVESTAV | Trapaga G.,CINVESTAV
Journal of Hydraulic Engineering | Year: 2013

This paper presents and discusses a simple method to deal with zero flows in Newton solvers for water distribution systems, in particular in a previously published global gradient algorithm. The method consists in replacing the Hazen-Williams head loss-flow relationship for flows below a certain threshold with a linear relationship, which coincides with Hazen-Williams' at zero, but has a nonzero derivative at that point, thus avoiding computational troubles associated with zero flows. Manual and automatic random testing of example networks shows that the proposed method compares well with both the algorithm adopted in water distribution modeling software and the recently proposed regularization method in convergence rate while outperforming them in computational veracity and applicability range. © 2013 American Society of Civil Engineers.


Shuvalov V.A.,Institute of Technical Mechanics | Kochubei G.S.,Institute of Technical Mechanics | Lazuchenkov D.N.,Institute of Technical Mechanics
High Temperature | Year: 2011

A procedure of diagnostics neutral and charged components of a collisional plasma with the help of a thermoanemometric cylindrical probe is developed. It is shown that temperature and volt-ampere characteristics of a probe make it possible to determine a complex of key kinetic parameters of charged and neutral particles in a collisional plasma. © 2011 Pleiades Publishing, Ltd.


Andreev M.V.,Dnipropetrovsk National University | Drobakhin O.O.,Dnipropetrovsk National University | Saltykov D.Yu.,Dnipropetrovsk National University | Gorev N.B.,Institute of Technical Mechanics | Kodzhespirova I.F.,Institute of Technical Mechanics
International Conference on Mathematical Methods in Electromagnetic Theory, MMET | Year: 2016

This paper presents a simple technique for the calculation of the eigenfrequencies of biconical cavities using the overlapping domain decomposition method in combination with the collocation method, which converges rapidly with increasing number of collocation point pairs and offers a reasonable computation speed. © 2016 IEEE.


Sherif K.,Linz Center of Mechatronics | Witteveen W.,Magna Powertrain | Puchner K.,Magna Powertrain | Irschik H.,Johannes Kepler University | Irschik H.,Institute of Technical Mechanics
AIAA Journal | Year: 2010

The present paper modifies and extends the recently developed equivalent static load method for the optimization of dynamically loaded linear elastic finite element systems with a huge number of degrees of freedom. In the equivalent static load method, dynamic loads have been transformed into equivalent static loads. This leads to an equivalent static response optimization with multiple loading conditions instead of a dynamic optimization problem. In the present paper, the equivalent static load algorithm is modified and extended by introducing a fatigue analysis in the iterative optimization procedure, where damage is used as suitable termination criterion of the iteration, as well as for the determination of a single and meaningful equivalent static load that leads to maximal damage in the structure. During the evolution process the structure is systematically stiffened by using the solid isotropic microstructure with penalization approach until a user-defined damage level is reached. Three standard examples from literature and an industrial application with a large number of degrees of freedom (600,000) demonstrate the computational efficiency of the proposed method. Copyright © 2010.

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