Shock–vortex interaction in transonic flow around a circular cylinder

Two-dimensional direct numerical simulations are performed to investigate shock–vortex interactions in transonic flow around a circular cylinder at R e D = 2000 and M a = 0.75 , 0.80, and 0.85. The wake-vortex evolution exhibits a quasi-periodic organization defined with reference to the motion of the surface shock. Each quasi-period consists of two stages: the newly formed vortex interacts mainly with the near-wake shock during Stage I, whereas the downstream vortex interacts primarily with the outer shear-layer shock during Stage II. Each stage contains local-concavity and splitting branches, whose combinations produce four vortex-evolution modes. An auxiliary ResNet3D–18 classifier is used to identify these modes and quantify their occurrence frequencies. The frequency of Mode II, characterized by Stage-I local concavity followed by Stage-II splitting, increases from 13.71% at M a = 0.75 to 40.26% at M a = 0.85 . Pressure-field analysis indicates that the shock-induced high-pressure regions are associated with changes in the surrounding streamline pattern and with the redistribution of ∂ u 2 /∂ x 1 near the vortex-deformation region. The instantaneous spanwise-vorticity transport fields show that convection provides the dominant background transport, whereas the localized compression and baroclinic contributions exhibit branch-dependent spatial overlap with the vortex-deformation region. Within the present two-dimensional, low-Reynolds-number configuration, these results provide a stage-based description of shock-induced vortex evolution in a canonical transonic cylinder wake.