Research on coherent structures in a mixing layer of the FENE-P polymer solution

The evolution of the coherent structures in a two-dimensional time-developi ng mixing layer of the FENE-P fluids is examined numerically. By the means of an appropriate filtering for the polymer stress, some characteristics of the coherent structures at high b were obtained, which Azaiez and Homsy di d not address. The results indicate that adding polymer to the Newtonian fl uids will cause stronger vorticity diffusion, accompanied with weaker funda mental and subharmonical perturbations and slower rotational motion of neig hbouring vortices during pairing. This effect decreases with the Weissenber g number, but increases with b. In addition, the time when the consecutive rollers are completely coalesced into one delays in the viscoelastic mixing layer compared with the Newtonian one of the same total viscosity.