Three-dimensionality of trajectories of experimental tracers in a steady axisymmetric swirling flow: Effect of density mismatch

The motion of tracer particles used for visualization in a steady axisymmetric swirling flow in a closed rotating disk-cylinder system is studied numerically. It is assumed that there exists a density mismatch between the particles and the fluid. It is shown that such a slight density mismatch leads to a deviation of the particle motion from steady axisymmetric streamlines, which in its turn yields non-axisymmetric patterns of the visualized flow. This gives a possible explanation for an existing disagreement between several experimental and numerical studies.