Asymptotic dispersion in 2D heterogeneous porous media determined by parallel numerical simulations

Jean-Raynald de Dreuzy (1) , Anthony Beaudoin (2) , Jocelyne Erhel (2)

1 GR - Géosciences Rennes
2 SAGE - Simulations and Algorithms on Grids for Environment

We determine the asymptotic dispersion coefficients in 2D exponentially correlated lognormally distributed permeability fields by using parallel computing. Fluid flow is computed by solving the flow equation discretized on a regular grid and transport triggered by advection and diffusion is simulated by a particle tracker. To obtain a well-defined asymptotic regime under ergodic conditions (initial plume size much larger than the correlation length of the permeability field), the characteristic dimension of the simulated computational domains was of the order of 103 correlation lengths with a resolution of ten cells by correlation length. We determine numerically the asymptotic effective longitudinal and transverse dispersion coefficients over 100 simulations for a broad range of heterogeneities s 2 [0, 9], where s 2 is the lognormal permeability variance. For purely advective transport, the asymptotic longitudinal dispersion coefficient depends linearly on s 2 for s 2 < 1 and quadratically on s 2 for s 2 > 1 and the asymptotic transverse dispersion coefficient is zero. Addition of homogeneous isotropic diffusion induces an increase of transverse dispersion and a decrease of longitudinal dispersion.

Keywords: Solute transport; asymptotic dispersion; parallel computing

Domains: Sciences of the Universe [physics]; Earth Sciences; Hydrology

Jean-Raynald de Dreuzy, Anthony Beaudoin, Jocelyne Erhel. Asymptotic dispersion in 2D heterogeneous porous media determined by parallel numerical simulations. Water Resources Research, 2007, 43, pp.W10439. ⟨10.1029/2006WR005394⟩. ⟨insu-00193397⟩