Berlin 2008 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe
CPP: Fachverband Chemische Physik und Polymerphysik
CPP 26: Micro and Nano Fluidics I: Liquids at structured materials
CPP 26.3: Vortrag
Mittwoch, 27. Februar 2008, 14:45–15:00, C 264
Morphological clues to wet granular pile stability — •Mario Scheel1, Marco Di Michiel2, Martin Brinkmann1, Ralf Seemann1,3, and Stephan Herminghaus1 — 1MPI for Dynamics and Self-Organization, Bunsenstr. 10, D-37073 Göttingen — 2European Synchrotron Radiation Facility, BP 220, F-38043 Grenoble Cedex — 3Experimental Physics, Saarland University, D-66041 Saarbrücken
When a dry granulate is mixed with a wetting liquid, the macroscopic stiffness of the latter is increased dramatically by virtue of the surface tension of the liquid. This macroscopic mechanic behavior is constant in a large range of the liquid content. Only if nearly all pores are filled with liquid, the stiffness weakens. Using X - ray micro tomography we explore the liquid morphologies that form within the granular pile, as function of liquid content, packing density and grain shape. We can clearly separate air, liquid and grains from each other, which allows to identify the emerging liquid morphologies. Capillary bridges were found for small liquid contents. If more liquid is added, the capillary bridges grow in size and eventually merge into larger liquid cluster. As even more liquid is added, the liquid cluster grow in size and merge with surrounding clusters. For randomly close packed grains this 'building principle' is still valid for large liquid contents and always results in a ramified liquid structure. This 'building principle' was verified numerically by minimizing the surface energy of particular cluster morphologies. The experimental observed constancy of the mechanic behavior follows from the ramified liquid structure.