Stretching of polymers in isotropic turbulence: a statistical closure.
We present a new closure for the mean rate of stretching of a dissolved polymer by homogeneous isotropic turbulence. The polymer is modeled by a bead-spring-type model (e.g., Oldroyd B, FENE-P, Giesekus) and the analytical closure is obtained assuming the Lagrangian velocity gradient can be modeled as a Gaussian, white-noise stochastic process. The resulting closure for the mean stretching depends upon the ratio of the correlation time for strain and rotation. Additionally, we derived a second-order expression for circumstances when strain and rotation have a finite correlation time. Finally, the base level closure is shown to reproduce results from direct numerical simulations by simply modifying the coefficients.
Vincenzi
Dario
D
Max Planck Institute for Dynamics and Self Organization, Bunsenstrasse 10, 37073 Göttingen, Germany.
Jin
Shi
S
Bodenschatz
Eberhard
E
Collins
Lance R
LR