Search

We built and characterised a macroscopic self-assembly reactor that agitates magnetic, centimeter- sized particles with a turbulent water flow. By scaling up the self-assembly processes to the centimeter-scale, the characteristic time constants also drastically increase. This makes the system a physical simulator of microscopic self-assembly, where the interaction of inserted particles is easily observable. Trajectory analysis of single particles reveals their velocity to be a Maxwell-Boltzmann distribution and it shows that their average squared displacement over time can be modelled by a confined random walk model, demonstrating a high level of similarity to the Brownian motion. The interaction of two particles has been modelled and verified experimentally by observing the distance between two particles over time. The disturbing energy (analogue to temperature) that was obtained experimentally increases with sphere size and differs by an order of magnitude between single-sphere and two-sphere systems (approximately 80 µJ versus 6.5 µJ, respectively). [ABSTRACT FROM AUTHOR]

The accuracy and the limits of validity of the discontinuous pressure model, which describes fluid flow inside a fracture using a subgrid scale approach, is assessed by comparing simulation results with those from direct simulation using Stokes flow. While the subgrid scale approach assumes a unidirectional flow, the Stokes model includes both velocity components. This is at the cost of meshing the interior of the fracture, which is here achieved through a spline-based mesh generation scheme. This scheme explicitly couples the spline representing the discontinuity to the fracture mesh and thereby alleviates the (re)meshing requirements for the interior of the fracture. The subgrid model and the direct simulation of Stokes flow approaches are compared by simulating a typical case containing a pressurised fracture, highlighting the advantages of using a subgrid model for the range in which its assumptions are valid, and showing its capabilities to accurately include the influence of the fracture on the porous material even outside this range. [ABSTRACT FROM AUTHOR]