Flow visualization studies of a turbulent drag reducing solution

A nondisturbing photochromic dye trace technique has been employed to study the flow profiles of water‐alcohol solutions containing the drag reducing polymer Polyox at concentrations of 0.55 to 5.5 ppm. Drag reductions of from 33 to 75% were observed in a smooth glass pipe. The dye traces show a thicker wall layer for the drag reducing solutions than that for the solvent alone. The core region is relatively unaffected by the polymer at 0.55 ppm and at 5.5 ppm the relative thickness of the turbulent core region has been greatly reduced. Earlier, unpublished work of Corinthios shows effectively no core at 33 ppm. Mean velocity and apparent axial turbulence intensity profiles obtained are in general agreement with previous data in the literature obtained with other methods and in the wall region the low frequency intensity is greater than that of the pure solvent. This is consistent with the results of Spangler but not those of Seyer. Higher low frequency intensities measured in the wall region suggest that higher frequency fluctuations are suppressed and/or that the time stability of eddies is increased as indicated by the reduced frequency of wall ejections in drag reducing solutions.