Revisiting the reattachment regime: a closer look at tandem cylinder flow at

Tandem cylinder flow comprises several different regimes. Within the reattachment regime, development of gap shear layers is utmost importance to flow, but has received little attention so far. Through direct numerical simulations at $Re = 10^{4}$ , for a ratio 3.0, we have discovered that are significantly altered with respect single cylinder. These differences include early onset separation, crossflow stabilising, delayed transition turbulence and meandering region. Vortex pairing in reported first time. The interaction between recirculating was investigated. Asymmetrical, large-scale vortices influence position through contact secondary flows. occurrence consequences both mechanism downstream wake. points unsteady large amplitude fluctuations on fine time scale. Reattachment seen be combination impingement modification upstream layers, which causes double layer near-wake. Buffeting by likely cause boundary layer. This leads significant changes wake topology, compared single-cylinder