Publica
Hier finden Sie wissenschaftliche Publikationen aus den FraunhoferInstituten. 3D simulation of the permeability tensor in a soil aggregate on basis of nanotomographic imaging and LBE solver
 Journal of soils and sediments 12 (2012), No.1, pp.8696 ISSN: 14390108 

 English 
 Journal Article 
 Fraunhofer ITWM () 
Abstract
Purpose
The purpose of this hydropedological work is to investigate the feasibility of a method to calculate permeability of soil peds on the matrix pore scale resolution. This paper focuses on imaging of the intraaggregate microstructure and, based on the threedimensional (3D) images, quantification of the pore network connectivity and permeability tensor. Finally, lattice Boltzmann equation (LBE) simulations of Navier–Stokes flow in the thus derived pore network allow to compute the heterogeneous 3D flow velocity field.
Materials and methods
Nanotomographic Xray absorption mode imaging of a single soil ped has been performed at the TOMCAT beamline of the Swiss Light Source synchrotron facility with 0.74 µm spatial resolution. Segmentation of the 3D NanoCT images into solid phase and pore space allowed to study the statistical properties of the connected pore network. The thus derived pore network data were used as direct input for the software package GeoDict integrated with a LBE algorithm to perform saturated water flow modeling.
Results and discussion
The soil ped features quantified from the tomographic images were pore and grain size distributions (PSD, GSD), porosity, percolation tensor in x, y, zdirection and percolation pathways (macropores). The PSD frequency has a peak in the range 38 µm (mesopores) contributing 50% of the total. In general, the matrix pore structure and, hence, saturated flow field velocity of our sample is highly anisotropic. LBEsimulated pore scale fluid flow is used to ultimately determine gross parameters (coefficients) of Darcy's law such as the saturated hydraulic conductivity, K s. The thus simulated K s = 105 ± 24 cm day1 of a single soil ped (mean of three ROIs and directions) is one order of magnitude higher than the value of K s = 12 ± 2 cm day1 predicted by a classical pedotranfer function approach. This K s underestimation by PTF is typical for macropore flow.
Conclusions
Integration of 3D image evaluation with the LBE approach as an essential step toward understanding the highly heterogeneous intraaggregate microstructure is now possible on the submicron scale. Modeling the resulting anisotropic fluid advection field is, however, just a first step for 3D models of biogeochemical reactions at soil interfaces on this pore scale.