Tribute to Krzysztof Wilmanski

Some 20 years ago, Krzysztof Wilmanski began his research into the theory of porous and granular media, fields that are addressed in this special issue of Acta Mechanica. In contrast to earlier models for such media, Wilmanski introduced the porosity as a material field, and he derived a particular balance equation for this quantity based on thermodynamic arguments. A principal application of the resulting continuum model has been the investigation of linear wave propagation. This was the topic of one minisymposium at the 8th European Solid Mechanics Conference in the Graz University of Technology, Austria, 9–13 July 2012.