On physical mechanisms in two- and three-dimensional separations

Some of the physical mechanisms that arise in interactions, upstream influe nce and separation are discussed for boundary layers and internal motions. Mechanism 1 involves pressure-displacement interaction, stemming from the G oldstein singularity and the issue of its removal. At least six other mecha nisms, 2-7, arise in more recent studies for two- and three-dimensional flo ws. These are in blade-wake rotary flows, where streamwise periodicity, inn er-outer interactions at very low incidence, and leading-edge jump effects enter the reckoning, and in surface-mounted roughness flows, concerning thr ee-dimensional upstream influence, pressure feedback and longitudinal (e.g. horseshoe) vortex formation.