  This work is an attempt to test the concept of hydrodynamic charge (analogous
to the electric charge in Electromagnetism) in the simple case of a coherent
structure such as the Burgers 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.
