The effect of buoyancy on vortex shedding in the near wake of a circular cylinder

The phenomenon of vortex shedding from a heated/cooled circular cylinder has been investigated numerically in the mixed natural and forced convection regimes. Accuracy of the computation was achieved by the fourth-order Hermitian relation applied to the contravariant velocity components in the convection terms of the vorticity transport equation, and by the far-boundary stream-function condition of an integral-series form developed by the authors. Purely periodic flows at Re = 100, efficiently established through the use of a direct elliptic solver called the SEVP, was found to degenerate into a steady twin-vortex pattern at the critical Grashof number 1500, confirming an earlier experimental observation identified as ‘breakdown of the Kármán vortex street’. Various other buoyancy effects about the heated/cooled cylinder are discussed by means of the flow patterns, the Nusselt number and the drag coefficient curves.