Eulerian and Lagrangian Statistics Of Homogeneous Polymeric Turbulence Using a Hybrid Eulerian Lagrangian Model

  • Crespi, Ludovico (Sapienza Università di Roma)
  • Serafini, Francesco (Sapienza Università di Roma)
  • Battista, Francesco (Sapienza Università di Roma)
  • Gualtieri, Paolo (Sapienza Università di Roma)
  • Casciola, Carlo Massimo (Sapienza Università di Roma)

Please login to view abstract download link

Polymeric liquids are non-Newtonian fluids that can give rise to remarkable phenomena. Among the possible methods capable to shed light on the matter, a numerical hybrid Eulerian-Lagrangian approach is a viable option since it has been proven capable of quantitatively replicating experimental results of turbulent drag reduction in pipes[1]. The goal of this work is to answer the following two Research Questions. RQ1 The high Weissenberg limit is equivalent to vanishing elasticity. Expecting a purely viscous in- teraction between polymers and fluid, how are typical turbulence observables altered by the presence of polymers? Note that this limit is inaccessible with Eulerian models like FENE-P due to the stability of the numerical method. The observables addressed are energy budgets in space and frequency domain, triadic transfer as in [2] and dissipation statistics. RQ2 Due to the nature of the system, a Lagrangian point of view should be able to highlight fundamental information about the system. The analysis focuses on classic fluid observables tracked at polymer po- sitions and conditioned to polymer extension. The conditioning is crucial since in the high Weissenberg limit extension acts like a switch that enables a back-reaction from the polymers only when the polymers sample an extending velocity gradient. Current available results all point towards the fact that polymers in HIT enhance the dissipation in the forcing and early iner- tial range. This suggests the following picture: polymers dissipate energy early in the cascade, which reaches a ‘new equi- librium’ in which turbulence is basically Newtonian, with polymers having on av- erage a marginal role. Concerning RQ2 research is ongoing.