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    Wyświetlanie 1-9 z 9
    Tytuł:
    Method of characteristics for design of centrifugal pump geometry
    Autorzy:
    Puzyrewski, R.
    Zochowski, K.
    Flaszyński, P.
    Powiązania:
    https://bibliotekanauki.pl/articles/1943212.pdf
    Data publikacji:
    2010
    Wydawca:
    Politechnika Gdańska
    Tematy:
    pumps
    inverse problem
    method of characteristics
    Opis:
    The method of characteristics leads to the blade geometry of a centrifugal pump. The method is built taking the advantage of the governing equations of fluid mechanics written in a non-orthogonal coordinates system. The coordinate system is based on an analytically described boundary of a centrifugal pump. Some of the information concerning the designed geometry should be introduced in advance. The mass conservation equation needs the information of the blockage factor resulting from the blading thickness. In the momentum conservation equation the body force replaces the blading force together with the friction force. In the energy conservation equation the dissipation effects are represented by a loss coefficient. It is shown that while simplifying the body force vector, the set of equations reduces to a hyperbolic system which allows applying the method of characteristics. The shapes of surfaces representing the designed blading can be built from the trajectories of fluid particles.
    Źródło:
    TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2010, 14, 3; 249-256
    1428-6394
    Pojawia się w:
    TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Simulation and discretization of random field in the slip-line method
    Autorzy:
    Przewłócki, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/240960.pdf
    Data publikacji:
    2003
    Wydawca:
    Polska Akademia Nauk. Instytut Budownictwa Wodnego PAN
    Tematy:
    bearing capacity
    method of characteristics
    random field
    Opis:
    The paper deals with the problem of bearing capacity of a strip footing based on the random subsoil. The solution has been obtained in a framework of the slip-line method. In order to include randomness of the soil medium, a modification of the method of characteristics is proposed. In such an approach, the stochastic finite difference method based on the Monte Carlo technique has been adopted. It enables including a spatial variability of soil properties into the analysis and to determine its influence on the variance of the ultimate collapse load. It is assumed that the soil medium is purely cohesive and only its cohesion can be considered as a random field. The simulation algorithm of multi-dimensional random field, based on the diagonalisation of the covariance matrix by a transformation using a lower-triangle matrix is described. The problems of the medium discretization and stabilization of the solution are discussed.
    Źródło:
    Archives of Hydro-Engineering and Environmental Mechanics; 2003, 50, 4; 343-358
    1231-3726
    Pojawia się w:
    Archives of Hydro-Engineering and Environmental Mechanics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Sufficient conditions for optimality for a mathematical model of drug treatment with pharmacodynamics
    Autorzy:
    Leszczynski, M.
    Ratajczyk, E.
    Ledzewicz, U.
    Schättler, H.
    Powiązania:
    https://bibliotekanauki.pl/articles/255130.pdf
    Data publikacji:
    2017
    Wydawca:
    Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
    Tematy:
    optimal control
    sufficient conditions for optimality
    method of characteristics
    pharmacodynamic model
    Opis:
    We consider an optimal control problem for a general mathematical model of drug treatment with a single agent. The control represents the concentration of the agent and its effect (pharmacodynamics) is modelled by a Hill function (i.e., Michaelis-Menten type kinetics). The aim is to minimize a cost functional consisting of a weighted average related to the state of the system (both at the end and during a fixed therapy horizon) and to the total amount of drugs given. The latter is an indirect measure for the side effects of treatment. It is shown that optimal controls are continuous functions of time that change between full or no dose segments with connecting pieces that take values in the interior of the control set. Sufficient conditions for the strong local optimality of an extremal controlled trajectory in terms of the existence of a solution to a piecewise defined Riccati differential equation are given.
    Źródło:
    Opuscula Mathematica; 2017, 37, 3; 403-419
    1232-9274
    2300-6919
    Pojawia się w:
    Opuscula Mathematica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    A numerical approach to the standard model of water hammer with fluid-structure interaction
    Autorzy:
    Henclik, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/281051.pdf
    Data publikacji:
    2015
    Wydawca:
    Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
    Tematy:
    water hammer
    transient pipe flow
    fluid-structure interaction
    standard model
    method of characteristics
    Opis:
    In the classic water hammer (WH) theory, 1D liquid flow in a quasi-rigid pipe is assumed. When the pipe is flexible or is fixed to the foundation with elastic supports, the dynamic fluid structure interaction (FSI) should be taken into account for more accurate modelling of the system behaviour. The standard model of WH-FSI for a straight pipe reach is governed by fourteen hyperbolic partial differential equations of the first order, two for 1D liquid flow and twelve for 3D motion of the pipe. This model is presented in the paper and an algorithm for its numerical solution based of the method of characteristics is proposed. Basic boundary conditions (BC) are shortly discussed. The important condition at the junction of two subpipes fixed to the foundation with a viscoelastic support is presented in details and a general method of its solution is proposed.
    Źródło:
    Journal of Theoretical and Applied Mechanics; 2015, 53, 3; 543-555
    1429-2955
    Pojawia się w:
    Journal of Theoretical and Applied Mechanics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Mathematical model and numerical computations of transient pipe flows with fluid-structure interaction
    Autorzy:
    Henclik, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/175378.pdf
    Data publikacji:
    2010
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    waterhammer
    transient pipe flow
    fluid-structure interaction (FSI)
    numerical modeling
    method of characteristics
    Opis:
    Transient flows in closed conduits are of interest from over a century, but the dynamic interaction between the fluid and the pipe is taken into consideration more thoroughly just from a few decades. A standard model of the phenomenon consists of fourteen first order partial differential equations (PDE), two for a one-dimensional (1D) liquid flow and twelve for 3D pipe motion. In many practical cases however, a simpler four equations (4E) model can be used, where 1D longitudinal pipe movement is assumed. A short description of waterhammer event with fluidstructure interaction taken into account is presented in the article. The 4E mathematical model is presented in detail with the assumptions and main algorithms of computer program that has been developed. Two phase flow is assumed not to take place, but the friction between the liquid and the pipe wall are taken into consideration. A method of characteristics (MOC) with time marching procedure is employed for finding the solutions, but instead of direct solving the resulting finite difference equations (FDE) the “wave method” is proposed. Some other important elements of the algorithm are presented and selected results of numerical computations as well.
    Źródło:
    Transactions of the Institute of Fluid-Flow Machinery; 2010, 122; 77-94
    0079-3205
    Pojawia się w:
    Transactions of the Institute of Fluid-Flow Machinery
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    A boundary condotions at modeling 1-D pulsating flows in pipes according to the method of characteristics
    Autorzy:
    Pałczyński, T.
    Powiązania:
    https://bibliotekanauki.pl/articles/246623.pdf
    Data publikacji:
    2012
    Wydawca:
    Instytut Techniczny Wojsk Lotniczych
    Tematy:
    1D simulations
    Valve boundary conditions
    method of characteristics
    pulsating flow at pipes
    Opis:
    At this paper, there were compared three conceptions of boundary conditions and their definition at partially opened pipes. This is typical at inlet and exhaust pipes of internal combustion engines and piston compressors. At an introduction there were listed the current state of affairs at a one dimensional modelling pulsations according to the Method of Characteristics (MOC). Subsequently, there was presented the main idea of MOC. At the third chapter there were presented general guidelines at initial and boundary conditions definition. Next there are three descriptions of the analyzed problem. Firstly, there was presented partially open end phenomena at space and stage plane. Secondly, there was shown the theory of acoustic wave propagation with description of stage waves at analyzed ends of pipe. Lastly, there is a new conception of constant pressure valve boundary conditions, which is the synthesis of the both mentioned earlier. At the fourth paragraph there was shortly presented existing test rig dedicated to research of pulsating flow in pipes. This test rig was built at Flow Metrology Division of Lodz University of Technology [9]. At the second part of this chapter there were shown main assumption of elaborated simulation algorithm at Matlab Simulink environment. Lastly there were discussed simulation results compared with presented conceptions of boundary conditions.
    Źródło:
    Journal of KONES; 2012, 19, 2; 395-402
    1231-4005
    2354-0133
    Pojawia się w:
    Journal of KONES
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Hydraulic transients analysis in pipe networks by the method of characteristics (MOC)
    Autorzy:
    Wichowski, R.
    Powiązania:
    https://bibliotekanauki.pl/articles/240954.pdf
    Data publikacji:
    2006
    Wydawca:
    Polska Akademia Nauk. Instytut Budownictwa Wodnego PAN
    Tematy:
    hydraulic transients
    method of characteristics
    single pipe
    experimental measurement
    pipe networks
    numerical simulations
    Opis:
    The paper presents results of an experimental and theoretical study of the hydraulic transients in straight pipes and numerical simulations of unsteady flow in pipe networks. A mathematical model consists of a set of partial differential equations of hyperbolic type, which have been transformed by the method of characteristics into ordinary differential equations which are solved by the predictor-corrector method. Experimental tests have been performed, in order to examine the hydraulic transients phenomenon, in a single straight steel pipe. The experiments were carried out in the hydraulic laboratory of the Institute of Water Supply and Water Engineering, Environmental Engineering Faculty, Warsaw University of Technology. The numerical results show that the presented one dimensional model for a single pipe correctly describes the phenomenon since there is a good agreement with experimental maximum and minimum oscillations. In the paper, selected exemplary equations in a difference form for the pipe networks are also presented. One calculation example is given relating to the complex water-pipe network consisting of 17 loops, 48 pipelines and 33 nodes, supplied by two independent sources. Water-hammer throughout the whole pipeline network was caused by closing the gate valve at mid-point of one selected pipe. The results of the numerical calculations are presented in graphic form with respect to the final cross-sections of pipes.
    Źródło:
    Archives of Hydro-Engineering and Environmental Mechanics; 2006, 53, 3; 267-291
    1231-3726
    Pojawia się w:
    Archives of Hydro-Engineering and Environmental Mechanics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Parameters affecting water hammer in plastic pipelines
    Autorzy:
    Urbanowicz, K.
    Firkowski, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/135271.pdf
    Data publikacji:
    2018
    Wydawca:
    Akademia Morska w Szczecinie. Wydawnictwo AMSz
    Tematy:
    water hammer
    unsteady flow
    viscoelastic pipes
    method of characteristics
    partial differential equations
    creep function
    Opis:
    Pressure pipes made of selected plastics are widely used in current water supply systems. Unfortunately, the theoretical basis for modeling transient flows in these pipes has not been clarified yet. For simplified one-dimensional numerical modeling, a model is commonly used in which the total deformation of the pipe walls is expressed by the sum of instantaneous and retarded deformations. One of the main problems lies in the correct experimental determination of the creep function defining the properties of the polymer. The influence of other parameters on which the numerical solution of the method of characteristics is based is the subject of the research presented in this paper.
    Źródło:
    Zeszyty Naukowe Akademii Morskiej w Szczecinie; 2018, 54 (126); 35-43
    1733-8670
    2392-0378
    Pojawia się w:
    Zeszyty Naukowe Akademii Morskiej w Szczecinie
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Symualcje jednowymiarowych przepływów pulsacyjnych w przewodach w oparciu o metodę charakterystyk
    Simulations of 1-D pulsating flow at pipes according to the method of characteristics
    Autorzy:
    Pałczyński, T.
    Powiązania:
    https://bibliotekanauki.pl/articles/395294.pdf
    Data publikacji:
    2012
    Wydawca:
    Stowarzyszenie Inżynierów i Techników Mechaników Polskich
    Tematy:
    jednowymiarowe modelowanie zjawisk pulsacyjnych w przewodach
    symulacje
    MATLAB/Simulink
    metoda charakterystyk
    one-dimensional pulsating phenomena in pipes modeling
    simulations
    MATLAB Simulink
    method of characteristics
    Opis:
    W pracy omówiono podstawowe informacje związane z koncepcją wykorzystania metody charakterystyk w modelowaniu przepływów w przewodach zasilanych pulsacyjnie. W dalszej części pracy zaprezentowano technologię opracowania modelu symulacyjnego. W końcowej części pracy przedstawiono przykładowe wyniki badań numerycznych, odniesione do badań eksperymentalnych, uzyskując potwierdzenie słuszności przyjętej koncepcji. Opisano główne zalety zaproponowanej koncepcji badań symulacyjnych a także kierunki dalszych badań
    At this paper there were presented basic information connected with concept of usage of Method of Characteristics at pipes with pulsating flow supplied modeling. At the next section of paper there were shown technology of simulation model building. Simulation results compared with experiment complained the wisdom of proposed conception. There were also presented the main advantages of described model and the next steps of research.
    Źródło:
    Postępy Nauki i Techniki; 2012, 14; 197-207
    2080-4075
    Pojawia się w:
    Postępy Nauki i Techniki
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-9 z 9

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