Mesh adaptive finite element formulation for moisture transfer in materials with a critical moisture content

Wetting or drying of most open porous building materials is characterized by a sharp moving waterfront. Due to the high moisture gradients at the waterfront, an accurate finite element simulation requires a very fine mesh. To reduce computational costs a mesh adaptive method based on the Arbitrary Lagrangian Eulerian (ALE) technique is proposed. To continuously relocate the nodes on the computational domain a remesh-indicator is equally distributed. In problems of water imbibition or drying of open porous building materials specific attention has been paid to the zone of critical moisture content. To this extent the traditional jump-based indicator, quantifying the jump of a selected state variable, has been modified into an area-based remesh-indicator. An error analysis of an academic example shows that the area-based indicator is superior to the jump-based one. To illustrate the capabilities of the remeshing method based on an area-based indicator, one and two-dimensional examples of water imbibition of ceramic brick and drying of cellulose fibre cement are included.