  We study experimentally a round Jet In CrossFlow (JICF) at low values of the
jet to-crossflow velocity ratio R using instantaneous and time-averaged
three-dimensions three-components (3D3C) velocimetry. The difference between
instantaneous and time-averaged swirling structures of the JICF is emphasized.
Through the analysis of spatial distribution of instantaneous transverse and
longitudinal vortices the main transitions of the JICF are characterized for
0.15 < R < 2.2. A new transition at very low velocity ratio is found (R < 0.3).
When R is large enough (R > 1.25), the classic JICF topology is recovered. In
between, a deformation of the classical JICF topology is observed consisting in
a progressive disappearance of the leading-edge vortices, a bending of the jet
trajectory and thus a strengthened interaction with the boundary layer. toward
the wall. Thanks to a state-of-the-art review on the JICF topology and using
visualizations of the flow structures extracted from our experimental
volumetric velocimetry measurements, this article provides a complete
transition scenario of the JICF topology from the high velocity ratios to the
lowest ones, and gives the topological transition threshold associated with
each kind of vortex.
