Using global node-based velocity in random walk particle tracking in variably saturated porous media: application to contaminant leaching from road constructions

Practical Implementation of New Particle Tracking Method to the Real Field of Groundwater Flow and Transport

“…Since the velocity is interpolated continuously over the model domain and the particle object knows the element index, the continuous velocity for the particle can be obtained along with the other subsequent properties, such as the dispersion tensor, derivative of velocity, and dispersion coefficient derivatives. Park et al (2008) showed that their proposed RWPT method successfully reduced the number of particles by approximately two orders of magnitude without losing the accuracy of the concentration contours. In examples for this study, the local mass conservation problem was avoided by assuming analytically known velocity fields, obtaining global node-based velocities from the known velocity distribution by superposing a spatial discretization mesh on the computational region, and by using the inverse distance method as a velocity interpolation.…”

“…Hence, computing the dispersion coefficient derivatives for RWPT using either FEM or FDM will yield erroneous values (Hoteit et al, 2002, Park et al, 2008. Therefore, the discontinuous velocity will result in local mass conservation errors unless a correction is made.…”

“…Within the knowledge of the author, almost all RWPT approaches have computed the advection movement of particles, using what we call a single velocity approach, that is, using only velocities at the old time level to compute the advection movement (Kinzelbach, 1986;LaBolle et al, 1996;Hassan et al, 1997;Hoteit et al, 2002;Tompson and Gelhar, 1990;Park et al, 2008). Although a single velocity approach does give a simple calculation because the velocities at the old time level are always known explicitly, it does not yield efficient results compared to other advanced advective particle tracking approaches (Cheng et al, 1996;Yeh, 2009, 2010;Bensabat et al, 2000).…”

“…Therefore, the discontinuous velocity will result in local mass conservation errors unless a correction is made. To prevent these errors, Park et al (2008) used the global node-based velocity originally proposed by Yeh (1981) to resolve the discontinuities of flow velocity at the element or cell boundaries and to obtain a continuous velocity map over the model domain. Since the velocity is interpolated continuously over the model domain and the particle object knows the element index, the continuous velocity for the particle can be obtained along with the other subsequent properties, such as the dispersion tensor, derivative of velocity, and dispersion coefficient derivatives.…”

Development of a 3D groundwater model based on scarce data: the Wadi Kafrein catchment/Jordan

“…OGS is programmed in C?? according to the object-oriented software concepts, and it can be used to simulate flow, mass, heat transport and deformation as well as chemical reaction processes in porous and fractured media (Miles et al 2007;Park et al 2008;Wang et al 2009). The implementation of numerical methods involving geometric description of geosystems with the application of finite element analysis is of vital importance for investigation and modelling of complex coupled nature or man-induced processes.…”