Strong polymer-turbulence interactions in viscoelastic turbulent channel flow

Abstract

This paper is focused on the fundamental mechanism(s) of viscoelastic turbulence that leads to polymer-induced turbulent drag reduction phenomenon. A great challenge in this problem is the computation of viscoelastic turbulent flows, since the understanding of polymer physics is restricted to mechanical models. An effective state-of-the-art numerical method to solve the governing equation for polymers modeled as nonlinear springs, without using any artificial assumptions as usual, was implemented here on a three-dimensional channel flow geometry. The capability of this algorithm to capture the strong polymer-turbulence dynamical interactions is depicted on the results, which are much closer qualitatively to experimental observations. This allowed a more detailed study of the polymer-turbulence interactions, which yields an enhanced picture on a mechanism resulting from the polymer-turbulence energy transfers.

On the role of pressure in elasto-inertial turbulence

“…In other words, the turbulence is mainly sustained by the polymers, as already recognised in previous studies [7,18,20]. On the other hand, the polymer production for the two other components of the diagonal is negative (see Figures 5(c)), indicating a transfer of energy from the flow to the polymers.…”

“…The second term, P p ij , is the polymer stress work. In particular, P p ii represents the transfer of energy between the mean turbulent kinetic energy and the mean elastic energy of the polymers [7,20]. This term can be either positive or negative, and a positive value corresponds to an energy transfer from the polymers to the turbulence.…”

Influence of length of polymer aggregation on turbulent friction drag reduction effect

“…Fujimura et al (2016) verified the bead-spring chain model through comparison with experiments and the finite elastic nonlinear extensibility-Peterlin (FENE-P) model, in which polymer dynamics is represented in the Eulerian frame of reference (Bird et al, 1987), and investigated the influence of the spring constant on the drag reduction effect. Their statistics are in good qualitative agreement with experimental results and with numerical results obtained using the FENE-P model (Dallas et al, 2010). Additionally, they analyzed the budget of Reynolds stress, and reported that the results for energy transport between turbulent flow and polymer models support the trends observed in the study with the FENE-P model by Dimitropoulos et al (2001).…”

Elasto-inertial turbulence

“…Time advancement uses the typical fractional step method utilized in most DNSs of turbulence. The rheological parameters adopted here are consistent with those used in previous simulations of polymer drag reduction (11,12,(44)(45)(46). We use a maximum polymer extension of L = 200, β = 0:9, and Wi* = 8.…”