EFFECT OF POLYMER ADDITIVES ON GORTLER VORTICES IN TAYLOR-COUETTE FLOW

Taylor-Couette flow is ideal for studying drag-reducing polymer additives because, unlike turbulent boundary layers, the instabilities are better understood. Video records of laser-induced fluorescence experiments with and without polymers will be presented. Polyethylene-oxide (PEG) 'oceans' were used in concentrations of 20 and 100 p.p.m. In the Taylor number range, 3 x 10(4) less than or equal to Ta less than or equal to 10(8), Newtonian flow consisted of Taylor vortices which span the gap between cylinders and much smaller Gortler vortices at the inner cylinder wall. Measurements of core-to-core separation between counter-rotating vortices were made to estimate the Gortler instability wavenumber. These measurements show that PEO addition increases the Gortler wavenumber for a given Taylor number. At the lower Taylor numbers, Gortler vortex formation was suppressed by PEG. This implies that polymers directly affect the evolution of centrifugal instabilities.