  An alternative step in understanding the flows of near wall drag-reducing
turbulence can be examining the flow in a well-organized streamwise vortex with
a laminar background. Herein, we studied the flow behaviors of the Giesekus
viscoelastic fluid in a rotating plane Couette flow system, which is
accompanied by steady roll cell structures. By fixing the Reynolds and rotation
numbers at values that provide as steady wavy roll cell, i.e., an array of
meandering streamwise vortices, the Weissenberg number was increased up to 2000
(where the relaxation time was normalized by the wall speed and the kinematic
viscosity). We observed that, in the viscoelastic flows, the secondary flow
(wall-normal and spanwise velocity fluctuations) are suppressed while the
streamwise component is maintained, and the wavy roll cells are modulated into
streamwise-independent straight roll cells. The kinetic energy transports among
the mean shear flow, Reynolds stresses due to the roll cell, and viscoelastic
stress are investigated in the non-turbulent background. We further discussed
the modulation mechanism and its relevance to the drag reduction phenomenon in
the viscoelastic wall turbulence.
