Numerical observation of transient phase of viscoelastic fluid counterflows

Abstract

Counterflows of the Oldroyd-B and De Witt viscoelastic fluids within the cross-channels are investigated numerically. The simulation is based on the pressure-correction method whose convergence has been analyzed and formally proved earlier. It is found that on the stabilization phase above some threshold Weissenberg numbers, the flow form undergoes essential restructuring on two found mechanisms: With moderate Reynolds numbers, the change of the counterflows is nearly stochastic whereas with smaller Re (less than 0.1), circular vortex-like structures arise in the vicinity of the counterflow central point. These structures are shown to be close to the phenomena observed before in experimental studies of such kind of flows where they are related to the class of purely elastic instability. It is also detected that at the moment, the vortex intensities reach their peaks as the counterflows change their directions. The reason of this change is found to be a specific combination of the flows nonstationary conditions and the fluid elastic nature.