Flnite Volume Method Research Articles

HYBRID FINITE DIFFERENCE/FINITE VOLUME METHOD FOR 3-D CONDUCTING MEDIA PROBLEMS

A hybrid time-domain method combing flnite-difierence and cell-centered flnite-volume method is presented in this paper. This method is applied to solve three dimensional electromagnetic problems which involve media having flnite conductivity. The fractional-step technique (FST) for FVTD scheme is applied to solve these problems. Local time-step scheme is used to enhance the e-ciency of this method. Numerical results are given and compared with a reliable numerical method, which is used to show the validation of this method.

A Numerical Study for the Performance of the WENO Schemes Based on Different Numerical Fluxes for the Shallow Water Equations

In this paper we investigate the performance of the weighted essential non-oscillatory (WENO) methods based on difierent numerical ∞uxes, with the objective of obtaining better performance for the shallow water equations by choosing suitable numerical ∞uxes. We consider six numerical ∞uxes, i.e., Lax-Friedrichs, local Lax-Friedrichs, Engquist-Osher, Harten-Lax-van Leer, HLLC and the flrst-order centered ∞uxes, with the WENO flnite volume method and TVD Runge-Kutta time discretization for the shallow water equations. The detailed numerical study is performed for both one-dimensional and two-dimensional shallow water equations by addressing the issues of CPU cost, accuracy, non-oscillatory property, and resolution of discontinuities.

Combined RKDG and LDG Method for the Simulation of the Bipolar Charge Transport in Solid Dielectrics

The space charge transport described by the convection-reaction equations is sim- ulated by using the Runge-Kutta discontinuous Galerkin (RKDG) method. Compared to the traditional flnite volume method, the RKDG method has higher accuracy and better perfor- mance of capturing the steep front in the charge proflle. Combined with the RKDG method, the local discontinuous Galerkin (LDG) method was adopted to solve the Poisson's equation instead of the previous boundary element method (BEM), in order that the numerical quadrature for the solution of the convection-reaction equations is replaced by analytical formulas. The bipo- lar charge transport under dc voltage is simulated by the RKDG+LDG method, which is more e-cient and produces identical results with those of the RKDG+BEM method. The space charge dynamics plays an important role on the degradation and the breakdown of solid dielectrics under the high voltage due to the intensiflcation of the local electric fleld. The transport of the difierent species of space charges under the electric fleld can be described by a set of convection-reaction equations coupled with the Poisson's equation. In our previous work, the RKDG method was utilized to solve the convection-reaction equations (1). Unlike the traditional QUICKEST method with the ULTIMATE ∞ux limiter (2,3), the RKDG method can handle the convection and the reaction terms simultaneously without incorporating the split procedure (4), and the high-order accuracy can be obtained without incorporating a wide stencil, which is more suitable for the shock capturing than the QUICKEST method (5). For the solution of the Poisson's equation, the local discontinuous Galerkin (LDG) method proposed by B. Cockburn etal. (5,6) is adopted in this paper instead of the generally used boundary element method (BEM) (7), in order to replace the numerical quadrature with analytical formulas in the RKDG weak formulation of the convection-reaction equations. This combined RKDG+LDG method is verifled by the simulation of the space charge transport in a low-density polyethylene (LDPE) sample under high dc voltage. The results show that the proposed method is more e-cient and produces identical space charge proflles with those of the RKDG+BEM method.

Numerical Model of Inductive Flowmeter

This article deals with physical and chemical processes during measurement with an inductive ∞owmeter. A theoretical model and an example of numerical solution are presented here. We prepared numerical models based on the combined flnite element method (FEM) and the flnite volume method (FVM) of one of the three variants and computed the output voltage of the ∞owmeter electrodes. The model joins the magnetic, the electric and the current flelds, the ∞ow fleld and a chemical nonlinear ion model. The results were obtained by means of the FEM/FVM as a main application in ANSYS software.

Properties and Numerical Simulation of CaCl2.6H2O Phase Change

This paper deals with the application of phase change materials (PCM) for thermal management of integrated circuits as a viable alternative to active forced convection cooling sys- tems. The paper presents an analytical description of melting and freezing process, an analytical solution of CaCl2.6H2O phase change in 1D and the results of a numerical model of phase change. The numerical model joins thermal fleld, air ∞ow with respects to material phase change. This numerical model was obtained by means combined of the flnite element method (FEM) and flnite volume method (FVM) applied as main method in ANSYS software.

Numerical Model of Optimization of the Lead-acid Accumulator Grids

This article deals with chemical processes during charging and discharging of the lead-acid accumulator. There is presented one shape of electrode grids in this work, but we researched more variants. We prepared numerical models based on the combined flnite element method (FEM) and flnite volume method (FVM) of those variants and computed current density distribution on the surface of electrodes. The model joins magnetic, electric and current flelds, ∞ow fleld and chemical nonlinear ion model. Results were obtained by means of the FEM/FVM as a main application in ANSYS software.

Model of a Reactor Chamber with Microwave Heating

This contribution brings the results obtained by numerical modeling of a reactor chamber design. The reactor chamber is intended for the preparation of oil. The chamber is designed for the operating frequency f = 2:4GHz with regulated microwave power. The power regulation allows the optimization of heat distribution in non-homogenous material with respect to chemical and physical material changes | phase changes. The paper presents a numerical model of a coupled problem. The coupled problem includes the radio frequency model and thermal fleld with non-linear thermal material. It was solved using sophisticated combined numerical method | the flnite element method (FEM) and the flnite volume method (FVM). The used material respects its own phase change from the liquid condition to the gas phase. The apparatus serves as an experimental prototype of the commercial one, that is currently being used by the ARS | Altman Recovery System Company.

Three-Dimensional Modeling of Air Flow and Pollutant Dispersion in an Urban Street Canyon with Thermal Effects

Effects of excess ground and building temperatures on airflow and dispersion of pollutants in an urban street canyon with an aspect ratio of 0.8 and a length-to-width ratio of 3 were investigated numerically. Three-dimensional governing equations of mass, momentum, energy, and species were modeled using the RNG k-ϵ turbulence model and Boussinesq approximation, which were solved using the flnite volume method. Vehicle emissions were estimated from the measured trafflc flow rates and modeled as banded line sources, with a street length and bandwidths equal to typical vehicle widths. Both measurements and simulations reveal that pollutant concentrations typically follow the trafflc flow rate; they decline as the height increases and are higher on the leeward side than on the windward side. Three-dimensional simulations reveal that the vortex line, joining the centers of cross-sectional vortexes of the street canyon, meanders between street buildings and shifts toward the windward side when heating strength is increased. Thermal boundary layers are very thin. Entrainment of outside air increases, and pollutant concentration decreases with increasing heating condition. Also, trafflc-produced turbulence enhances the turbulent kinetic energy and the mixing of temperature and admixtures in the canyon. Factors affecting the inaccuracy of the simulations are addressed.