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Finite-difference Approach (finite-difference + approach)

Distribution by Scientific Domains

Engineering	100%

Selected Abstracts

Using PHREEQC to Simulate Solute Transport in Fractured Bedrock

GROUND WATER, Issue 4 2007
David S. Lipson
The geochemical computer model PHREEQC can simulate solute transport in fractured bedrock aquifers that can be conceptualized as dual-porosity flow systems subject to one-dimensional advective-dispersive transport in the bedrock fractures and diffusive transport in the bedrock matrix. This article demonstrates how the physical characteristics of such flow systems can be parameterized for use in PHREEQC, it provides a method for minimizing numerical dispersion in PHREEQC simulations, and it compares PHREEQC simulations with results of an analytical solution. The simulations assumed a dual-porosity conceptual model involving advective-reactive-dispersive transport in the mobile zone (bedrock fracture) and diffusive-reactive transport in the immobile zone (bedrock matrix). The results from the PHREEQC dual-porosity transport model that uses a finite-difference approach showed excellent agreement compared with an analytical solution. [source]

A new modification of the immersed-boundary method for simulating flows with complex moving boundaries

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 11 2006
Jian Deng
Abstract In this paper, a new immersed-boundary method for simulating flows over complex immersed, moving boundaries is presented. The flow is computed on a fixed Cartesian mesh and the solid boundaries are allowed to move freely through the mesh. The present method is based on a finite-difference approach on a staggered mesh together with a fractional-step method. It must be noted that the immersed boundary is generally not coincident with the position of the solution variables on the grid, therefore, an appropriate strategy is needed to construct a relationship between the curved boundary and the grid points nearby. Furthermore, a momentum forcing is added on the body boundaries and also inside the body to satisfy the no-slip boundary condition. The immersed boundary is represented by a series of interfacial markers, and the markers are also used as Lagrangian forcing points. A linear interpolation is then used to scale the Lagrangian forcing from the interfacial markers to the corresponding grid points nearby. This treatment of the immersed-boundary is used to simulate several problems, which have been validated with previous experimental results in the open literature, verifying the accuracy of the present method. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Modelling and simulation of fires in vehicle tunnels

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 3 2004
I. Gasser
Abstract Applying a low-Mach asymptotic for the compressible Navier,Stokes equations, we derive a new fluid dynamics model,which should be capable to model large temperature differences in combination with the low-Mach number limit. The model is used to simulate fires in vehicle tunnels, where the standard Boussinesq-approximation for the incompressible Navier,Stokes seems to be inappropriate due to the high temperatures developing in the tunnel. The model is implemented using a modified finite-difference approach for the incompressible Navier,Stokes equations and tested in some realistic fire events. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Time-domain sensitivity analysis of planar structures using first-order one-way wave-equation boundaries

INTERNATIONAL JOURNAL OF NUMERICAL MODELLING: ELECTRONIC NETWORKS, DEVICES AND FIELDS, Issue 5 2008
Peter A. W. Basl
Abstract An efficient adjoint variable method technique is developed for time-domain sensitivity analysis of planar structures with transmission-line modeling complemented by a first-order one-way wave-equation absorbing boundaries. A backward-running adjoint simulation is derived and solved. The validity of the technique is illustrated through three microstrip circuits. The examples demonstrate the efficiency and accuracy of the technique in comparison with the classical finite-difference approaches to the estimation of the response sensitivities. Copyright © 2007 John Wiley & Sons, Ltd. [source]