Description:

Title: Wetting of complex materials

Speaker: Stephan Herminghaus, Max Planck Institute for Dynamics and Self-Organization; University of Göttingen

Abstract: Wetting phenomena are usually studied with respect to idealized model substrates, which only remotely represent the complexity of surfaces relevant to industrial and everyday life scenarios. A paradigmatic example is fluid invasion in porous media, which is relevant to drying of filter cakes, irrigation, oil recovery, and many more. Both the roughness of the grains of the wetted material and the geometry of their packing render the morphology of the wetting front extremely complex, such that it has been impossible so far to develop predictive models for wetting fronts in such media. It is demonstrated that by careful choice of the descriptors of the porous material, it is possible to gain quite detailed insight into the physics of fluid displacement, and to predict quantities like the residual saturation of the defending fluid in relevant cases. We identify a universal filling transition on natural random roughness, similar to what is well known for many model geometries. Quite surprisingly, we find that Gaussian roughness models fail to account for this transition. It is furthermore shown that some important aspects of the invading fluid front morphology can be predicted on the basis of rather simple geometric considerations, in spite of the random nature of the material.

Host: Adilson Motter

Keywords: Physics, Astronomy, Complex Systems