Spread of infectious agents through the air in complex spaces.

The fluid mechanical processes that govern the spread of infectious agents through the air in complex spaces are reviewed and the scientific gaps and challenges identified and discussed. Air, expelled from the nose and mouth, creates turbulent jets that form loosely coherent structures which quickly slow. For the transport and dispersion of aerosols, the suitability of the Eulerian as well as the Lagrangian approaches are brought into context.

Turbulence and columnar vortex formation through inertial-wave focusing.

In this experimental and numerical study, we consider the role of inertial waves in the inverse energy cascade and the transfer of momentum in a rotating fluid. An oscillating torus generates two inertial-wave cones with their energy focusing at their apex. For high wave amplitudes, turbulence is generated locally around the focal point, resulting in angular momentum mixing and the generation of a columnar cyclonic vortex.