Effects of the extensional rheological properties of polymer solutions on vortex shedding and turbulence characteristics in a two-dimensional turbulent flow

An experimental study was performed to investigate the relationship between the extensional rheological properties of polymer solutions and vortex deformation in turbulent flow. Polyethyleneoxide as a flexible polymer and hydroxypropyl cellulose as a rigid polymer are added to two-dimensional (2D) turbulent flow. Specifically, 2D flow is advantageous as it examines the effect of the extensional rheological properties of polymers on the flow. In the study, 2D turbulent flow and vortex shedding in 2D turbulent flow were observed using interference patterns and particle image velocimetry (PIV). Power spectrum of the 2D flow images and 2D turbulence statistics calculated by PIV analysis indicated that there are three flow regimes of vortex shedding in the 2D turbulent flow of the polymer solution. The vortex shedding in the 2D flow was categorized into three types, and this was affected by the relaxation time of the polymer solutions.