Shear-induced anisotropy of effective thermal conductivity in granular packings

This work explores shear-induced anisotropy of the effective thermal conductivity (ETC) in granular packings when subjected to quasistatic shear deformation. The discrete element method is adopted to track the position, force, and contact condition of every particle in the packing during the shear process. The ETC of the packing at different shear strains is evaluated using the particle-resolved finite element method. The simulation results show that the anisotropy ratio of the ETC can reach 40% as the shear strain increases to 0.11. The increase of the anisotropy mainly results from the variation of the network formed by the contacts that exist in two consecutive shear steps. It is also proved that contacts with large contact radius and strong thermal conductance are preferentially aligned with the direction of the applied deformation. The non-uniform distribution of the contact radius and the preferential orientation of the contacts contribute to the anisotropy of the thermal conductivity. Finally, by grouping the contacts in a packing into sub-networks with either weak or strong contact, it is shown that the thermal conductivity anisotropy of a packing is mainly caused by strong contacts.