  We apply the recent frame-invariant theory of separation spike formation to
complex unsteady flows including a turbulent separation bubble, an impinging
jet, and flows around a freely moving cylinder and a freely rotating ellipse.
We show how the theory captures the onset of material spike formation, without
any assumption on the flow type (steady, periodic, unsteady) or separation type
(on- or off-wall, fixed or moving boundaries). We uncover new phenomena, such
as the transition from on-wall to off-wall separation, the merger of initially
distinct spikes, and the presence of severe material spikes that remain hidden
to previous approaches. These results unveil how an involved network of spikes
arises, interacts, and merges dynamically, leading to the final ejection of
particles from the wall in highly transient flow separation processes.
