Statistics and dynamics of the boundary layer reattachments during the drag crisis transitions of a circular cylinder

The intermittent nature of the laminar separation bubble on a cylinder in uniform flow

“…This observation is in line with that reported byCadot et al (2015) andMiau et al (2011) who also found weakening of Karman vortex shedding beyond a certain Re. The increase in the suction near the two shoulders of the cylinder, with increase in Re, is apparent from these spacetime diagrams.…”

“…This suggests that the asymmetry in the transition of the flow on the two sides of the cylinder is a consequence of a slight asymmetry in either the geometry or the flow conditions at the inlet. Cadot et al (2015) reported two kinds of boundary layer reattachment during the critical regime: symmetric and asymmetric. In the asymmetric scenario two kinds of transition are possible.…”

Sharp Transition in the Lift Force of a Fluid Flowing Past Nonsymmetrical Obstacles: Evidence for a Lift Crisis in the Drag Crisis Regime

“…A sharp increase of the lift with the Reynolds number for thick profiles at zero incidence has already been reported in the past [13], but its origin and similarity to the drag crisis seems to have been largely unnoticed. Note that the term lift crisis was previously used for a symmetrical obstacle in another meaning: to refer to the modification in the amplitude of the instantaneous lift fluctuations [9,[14][15][16]. Here the expression lift crisis is used to refer to the abrupt jump of the time-averaged lift.…”

Fast-response underwater TSP investigation of subcritical instabilities of a cylinder in crossflow

“…These flow features are characteristic to the precritical regime, whereas several authors (Bearman 1969;Farell and Blessmann 1983 among others) report a relevant increase in St as the flow enters the one-bubble regime. The flow dynamics during this latter state, as recently shown by Cadot et al (2015), is characterized by specific stable states before local permanent reattachment occurs. Nonetheless, the intermittent existence of a secondary separation line for Re > 150,000 suggests that although the turbulent boundary layer is not established, the flow regime is approaching this state.…”

“…The latter is defined as the flow condition where the shear layers undergo sufficient transition to reattach to the surface, thus originating a thin, bubble-like, separated region. Its occurrence was identified by Gerard (1978) as a distinctive mark of the transition-in-boundary-layer state, and recently, its dynamics was investigated by Cadot et al (2015).…”