Influence of nano- and micro-roughness on vortex generations of mixing flows in a cavity

Abstract

Experiments were carried out in a water-filled elongated cup of a “kitchen scale,” where motion was created by a rotating disk with various micro- and nano-roughness in the top of the cup. The obtained results have shown that for some patterns of nanostructures, there is a noticeable growth of a vortex, generated by the disk, while other roughnesses do not make visible changes in the flow structure. The results are of interest in assessing the efficiency of surfaces with nanoscale roughnesses. Indeed, the first type of nano-roughness may become useful for enhancing soft mixing in chemical and bio-reactors, including in the preparation of special food delicacies. On the other hand, the use of nanostructured surfaces that do not affect the main flow can help to solve some industrial problems of water and ice erosion, for example, in wind turbines or any other objects where disturbances of the main flow are undesirable.