Recent progress in microgravity-enabled, contactless manipulation methods based on thermovibrational forcing of particle suspensions has opened promising frontiers for fabricating high-performance materials in space. Here, a step is taken to expand this framework to encompass situations in which the dispersed phase consists of fibers rather than spherical inclusions. The problem is tackled numerically using a four way coupling methodology, which tracks the motion, rotation, and collisions of individual fibers with high fidelity. In parallel, the carrier fluid is resolved through integration of the Navier–Stokes equations in their complete non-linear form. It is shown that the mechanism driving dispersed matter self-organization is still operative when fibers of various aspect ratios are considered in place of spheres. Nevertheless, the aggregation phenomena are mediated by new effects strictly related to how fibers move, align, and interact with the surrounding boundaries. As a result of such increased complexity, the degree of particle accumulation and the clustering process itself exhibit a non-trivial dependence on the fiber aspect ratio. While for low-aspect ratio fibers, anisotropy enhances alignment and wall-induced accumulation, leading to denser and more compact structures, when much more elongated fibers are considered, the self-assembly process is adversely affected by frequent steric interactions, rotational constraints, and collective rearrangements.
Santhosh et al. (Mon,) studied this question.