The influence of polyvinylacetate additive in water on turbulent velocity field and drag reduction

The effect of polymer concentration on drag reduction was studied experimentally with diluted water solutions of polyvinylacetate in a 2.4 cm I. D. pipe. The instantaneous local velocities of the velocity fields were measured by a one-channel differential laser-Doppler anemometer DISA Mark II, with forward scattering. Concentrations of water-polyvinylacetate over the range from 10 to 2,000 ppm were used. The drag reduction coefficient is proportional to the concentration and hydrolysis degree of the saponificated polyvinylacetate (PVAC) employed. A mechanical degradation in the turbulent shear flow was not observed.List of Symbols a₁ coefficient in Eq. (3) - a₂ coefficient in Eq. (3) - D pipe diameter - k coefficient in modified Blasius equation for friction factor - K consistency parameter given by (1 b) - K_i coefficients in Eq. (5) - m coefficient in Eq. (3) - n flow index Eq. (1a), coefficient in Eq. (3) - n⁺ dimensionless position parameter defined by Eq. (4) - N⁺ position parameter defined by Eq. (7) - r radial distance from the pipe center - R pipe radius - Re Reynolds number - Re_g generalized Reynolds number, Eq. (9) - t temperature - u⁺ dimensionless local velocity, /u^* - u^* dynamic friction velocity, w(/8)^0,5 - U⁺ dimensionless local mean velocity defined by Eq. (6) - time-averaged local velocity - _m time-averaged local velocity at the pipe center - w average velocity over the cross-section of the pipe - X concentration of polymer in water, w · ppm - y distance from the pipe wall - y⁺ dimensionless distance from the pipe wall, y u^*/ or as in Eq. (8) - friction factor in drag reduction flow - ₀ friction factor of pure water - degree of drag reduction - viscosity - standard deviationA version of this paper was presented at the 9th National Symposium on the measurement of turbulence with laser Doppler and other anemometers, Bratislava, CSSR, 1986