TURBULENCE STRUCTURE OF DILUTE POLYMER AND SURFACTANT SOLUTIONS IN ARTIFICIALLY ROUGHENED PIPES

Pressure drop and velocity profile measurements are presented for turbulent flows of drag reducing fluids. The investigation was done in two rough pipes, known as ''k''- and ''d''-type rough pipes. The results are compared with those obtained in hydraulically smooth pipe of identical diameter. The spatial arrangement of the roughness elements in the pipe determines the parallel shift in the elastic sublayer and in the core region of the dimensionless turbulent velocity profile. The slopes of the velocity profiles in these regions remain unaffected by the arrangement which is an indication that the hydrodynamic influence of the roughness is restricted to the near-wall region. The drag reducing surfactant solution exhibited a drag reduction in the smooth as well as in the rough pipes which was higher than that given by Virk's maximum drag reduction asymptote. For this solution no influence of the roughness on the turbulence was detected when the dimensionless roughness height in viscous units was less than 12.