The paper describes qualitative analysis of contaminant transport in a homogeneous, isotropic aquifer where first order chemical reaction at the boundary and nonlinear decay act simultaneously. In order to analyze the relative merits, two types of disposal scheme are considered; (i) Scenario I: longer duration with low input concentration and (ii) Scenario II: short duration with higher input concentration. The governing advective-dispersion equation is solved numerically by employing ADI scheme under finite difference method. We apply the method of moments to investigate mean concentration distribution and other statistical parameters such as central moment, coefficients of skewness (β2 ) and kurtosis (β 3 ). The mean concentration distribution ( Cm ) is computed by applying Edgeworth’s asymptotic series for non-Gaussian curves involving Hermite polynomials ( Hn ). The forward displacement of centroid ( Xg ) with time, deviations of mean concentration distribution from Gaussianity and breakthrough curves have been examined. and Príspevok obsahuje kvalitatívnu analýzu transportu kontaminantov v homogénnej, izotropnej zvodni, na hraniciach ktorej simultánne prebiehajú chemické reakcie prvého rádu a nelineárny rozpad. Aby sme mohli posúdiť relatívne výhody spôsobu analýzy, použili sme dva typy schém; (i) Scenár I: nízka koncentrácia vstupov a ich dlhšie trvanie; (ii) Scenár II: krátko trvajúce vysoké koncentrácie vstupov. Advektívnodisperzná rovnica je riešená numericky, s využitím schémy ADI v rámci metódy konečných rozdielov. Na určovanie rozdelenia priemerných koncentrácií a iných štatistických parametrov, ako je centrálny moment, koeficient šikmosti (β2 ) a strmosť (β 3 ) , použili sme metódu momentov. Rozdelenie priemerných koncentrácií ( Cm ) sme vypočítali aplikáciou Edgeworthových asymptotických radov negaussovských kriviek, obsahujúcich Hermitove polynómy ( Hn ). Študovali sme dopredný posun centroidu ( Xg ) v závislosti od času, odchýlky od priemerných hodnôt rozdelenia priemerných koncentrácií od gaussovských, a určili sme tiež prienikové krivky.
The project is concerned with non-convectional direct stator winding slot cooling using water. The aim is to find optimal algorithm for control of water cooling. The control algorithms are tested on the experimental device, which is part of real synchronous machine with permanent magnets. The thermal model was built as a base for computational model of a machine without thermal sensors. The thermal model is possible used as predictor of machine heating in real time. This type of water cooling shows better effect on the machine heating than common water cooling system on the cover. and Obsahuje seznam literatury
The paper is concerned with computational simulation of stator winding heating of the synchronous machine. Software ANSYS 8.0 was used for computational simulation. Computational model considers heat pipe in the middle of winding slot. The results of computer simulation show the effect of direct winding cooling with water. The results of both methods of cooling were compared. Experimental device was created for verification of computational simulations. and Obsahuje seznam literatury
The flow of a mixture of liquid and solid particles at medium and high volume fraction through an expansion in a rectangular duct is considered. In order to improve the modelling of the phenomenon with respect to a previous investigation (Messa and Malavasi, 2013), use is made of a two-fluid model specifically derived for dense flows that we developed and implemented in the PHOENICS code via user-defined subroutines. Due to the lack of experimental data, the two-fluid model was validated in the horizontal pipe case, reporting good agreement with measurements from different authors for fully-suspended flows. A 3D system is simulated in order to account for the effect of side walls. A wider range of the parameters characterizing the mixture (particle size, particle density, and delivered solid volume fraction) is considered. A parametric analysis is performed to investigate the role played by the key physical mechanisms on the development of the two-phase flow for different compositions of the mixture. The main focuses are the distribution of the particles in the system and the pressure recovery.
In this paper a problem of multiple solutions of steady gradually varied flow equation in the form of the ordinary differential energy equation is discussed from the viewpoint of its numerical solution. Using the Lipschitz theorem dealing with the uniqueness of solution of an initial value problem for the ordinary differential equation it was shown that the steady gradually varied flow equation can have more than one solution. This fact implies that the nonlinear algebraic equation approximating the ordinary differential energy equation, which additionally coincides with the wellknown standard step method usually applied for computing of the flow profile, can have variable number of roots. Consequently, more than one alternative solution corresponding to the same initial condition can be provided. Using this property it is possible to compute the water flow profile passing through the critical stage.
The computational model of the reed-based element is in scope of this article. This element is studied for its potential suitability to generate an arfificial source voice. Compressed air is being used like a source of the energy to produce the voiced speech (similar to the healthy voiced speech). Two-way iteraction of solid and fluid part of the computational model has been considered for the solution. Computation has been performed by the finite element method (Ansys) and results have been processed by the sofsware MATLAB. Basic characteristics like a frequency spectrum and a fundamental frequency of generated source voice are evaluated. Relationship between deformation of the reed and the pressure in front of the reed is presented. This characteristic represents one of the basic phonation theories which are in our scope. This theory is based on the compressed air ‘bubble‘. and Obsahuje seznam literatury
This paper presents a brief review of selected approaches used for computational modelling of bimaterial failure and for evaluation of interface failure resistance. Attention is paid to the approaches that assume absence of initial interface crack. The applicability of such approaches to rubber-steel interface failure evaluation is discussed in the paper. The approach based on the so called ‘cohesive zone model‘ is preferred and demonstrated by an example of computational modelling of rubber-steel interface failure during a peel-test. The results of peel-test computational modelling are presented. The influence of cohesive zone element number on the results is also analysed. The results are consistent with experimental data. and Obsahuje seznam literatury
Experimentally based models of cardiac cells have been developed since 1960.The early models were based on extension of the Hodgkin-Huxley nerve impulse equations. Including only a few membrane currents they were able to successfully reconstruct the depolarization and repolarization of cellular membrane. Since that time, the models have underwent extensive modifications and reached a high degree of physiological detail. This short review is aimed to outline the history of their development and show the importance of computer modelling for the research in cardiac cell electrophysiology. and Obsahuje seznam literatury
The paper investigates ways to model the response of vibro-isolation mounts that utilise viscoelastic materials. Simple models based on linear and nonlinear static stiffness are developed. Dynamic response is approximated through appropriate scaling of the viscoelastic Young's modululs and use of the measured material loss factor. The approach is validated using cylindrical mounts made of polyurethane. The response of a 68 kg mass supported by two mounts and subjected to two different high-amplitude shock loads is predicted. Measured and predicted behaviour correlate closely for the nonlinear model while the linear model gives a reasonable representation. It is noted that the sensitivity of such mounts to temperature is high: the change in response associated with a temperature excursion of 10 °C is significantly greater than the inaccuracy involved with using the linear model. and Obsahuje seznam literatury
This work presents a numerical solution for the process of mixing gaseous fuels with air in the combustion chamber of an engine. The combustion parameters are influenced to a considerable degree by the characteristics of the mixture before its ignition. These characteristics can be influenced by the process of formation of the fuel and air mixture. Under certain simplified circumstances this process can be reproduced by means of commercially available software, and the results generated can be used
for the optimisation of the engine performance. and Obsahuje seznam literatury