The response of water and 20 ppm. solutions of Separan AP-30 and Polyox WSR 301 to the periodic motion of a thin sleeve was measured using a laser Doppler velocimeter. The sleeve was moved in an axial direction by an external coupling a t frequencies from '/4 to 1.0 Hz and a t amplitudes of h t o 2 in. The flow field downstream of the disturbance was found to consist of three regions: 1. a near field with a separation wake from the sleeve moving toward the pipe centerline; 2. an intermediate field in which alternate laminar and turbulent slugs passed a point; and 3. a far field with decaying turbulent flow. Differences in the behavior of water flows and polymer flows appeared i n each region. In the near field, wakes spread faster in water flows. In the intermediate field, the laminar slugs disappeared into turbulence more rapidly in water flows. And in the far field, the turbulence was not as developed in the polymer flows.
Detailed statistical evaluations were made on the signals in each region for a Reynolds number of 2000. The response of the dilute polymer solutions appeared to be governed by the initial interaction with the sleeve. Fewer high frequencies were generated than in the pure solvent so the periodic disturbance persisted downstreom. In pure water the eddies from the separation wake interacted strongly with the periodic disturbance leading to rapid decay of the periodic portion. Shear rates were not high enough to attribute the dilute polymer differences to vixoelastic effects.