  This study explores the dynamics of finite-size fibers suspended freely in a
viscoelastic turbulent flow. For a fiber suspended in Newtonian flows, two
different flapping regimes were identified previously by Rosti et al (2018).
Here we explore, how the fiber dynamics is modified by the elasticity of the
carrier fluid by performing Direct Numerical Simulations of a two-way coupled
fiber-fluid system in a parametric space spanning different Deborah numbers,
fiber bending stiffness and the linear density difference between fiber and
fluid. We examine how these parameters influence various fiber characteristics
such as the frequency of flapping, curvature, and alignment with the fluid
strain and polymer stretching directions. Results reveal that the
neutrally-bouyant fibers, depending on their flexibility, oscillate with large
and small time scales transpiring from the flow, but the smaller time-scales
are suppressed as the polymer elasticity increases. Polymer stretching is
uncommunicative to denser-than-fluid fibers, which flap with large time scales
from the flow when flexible and with their natural frequency when rigid. Thus,
the characteristic elastic time scale has a subdominant effect when the fibers
are neutrally-bouyant, while its effect is absent when the fibers become more
inertial. Additionally, we see that the inertial fibers have larger curvatures
and are less responsive to the polymer presence, whereas the neutrally-bouyant
fibers show quantitative changes. Also, the neutrally-bouyant fibers show a
higher alignment with the polymer stretching directions compared to the denser
ones. In a nutshell, the polymers exert a larger influence on neutrally-bouyant
fibers compared to the denser ones. The study comprehensively addresses the
interplay between polymer elasticity and the fiber structural properties in
determining its response behaviour in an elasto-inertial turbulent flow.
