Effect of rotation on buoyant plume dynamics

The aim of this work is the evaluation of the influence of the rotation on the turbulence and on the entrainment within a buoyant plume. A series of laboratory experiments are performed in the rotating water tank of the Turlab in Torino (Italy) producing negatively buoyant plumes emitted from a finite circular source, with varying plume density and background rotations. Thanks to the particle image velocimetry technique, we obtain a detailed description of the velocity field within the plume. We present the results in term of mean velocity, turbulence and vorticity fields. The swirling strength analysis is also performed to identify the coherent structures. Finally, the velocity spectra are examined. We find that the rotation affects the dynamics of the plume increasing the turbulence and, in particular, the number of structures developed along the plume edges, which feeds the entrainment. The analysis of the mean velocity fields also allows us to quantify the turbulent entrainemnt of ambient fluid within the buoyant plume, and discuss the role of rotation in this process.