Flow pattern transition accompanied with sudden growth of flow resistance in two-dimensional curvilinear viscoelastic flows - Nonlinear Sciences > Pattern Formation and SolitonsReportar como inadecuado




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Abstract: We find three types of steady solutions and remarkable flow patterntransitions between them in a two-dimensional wavy-walled channel for low tomoderate Reynolds Re and Weissenberg Wi numbers using direct numericalsimulations with spectral element method. The solutions are called-convective- -transition-, and -elastic- in ascending order of Wi. In theconvective region in the Re-Wi parameter space, the convective effect and thepressure gradient balance on average. As Wi increases, the elastic effectbecomes suddenly comparable and the first transition sets in. Through thetransition, a separation vortex disappears and a jet flow induced close to thewall by the viscoelasticity moves into the bulk; The viscous drag significantlydrops and the elastic wall friction rises sharply. This transition is caused byan elastic force in the streamwise direction due to the competition of theconvective and elastic effects. In the transition region, the convective andelastic effects balance. When the elastic effect dominates the convectiveeffect, the second transition occurs but it is relatively moderate. The secondone seems to be governed by so-called Weissenberg effect. These transitions arenot sensitive to driving forces. By the scaling analysis, it is shown that thestress component is proportional to the Reynolds number on the boundary of thefirst transition in the Re-Wi space. This scaling coincides well with thenumerical result.



Autor: Hiroki Yatou

Fuente: https://arxiv.org/







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