On the Lamb Vector and the Hydrodynamic Charge
Résumé
This work is an attempt to test the concept of hydrodynamic charge (analogous to the electric charge in Electromagnetism) in a simple case of a coherent structure such as the Lamb-Oseen vortex. We provide experimental measurements of both the so-called Lamb vector and its divergence (the charge) by two-dimensional Particle Image Velocimetry. In addition, we perform a Helmholtz-Hodge decomposition of the Lamb vector in order to explore its topological features. We compare the charge with the well-known Q criterion in order to assess its interest in detecting and characterizing coherent structure. Usefulness of this concept in studies of vortex dynamics is demonstrated.