Abstract:

In order to improve the drag reduction effects of surfactant dilute aqueous solution at low Reynolds numbers in a pipe flow, experiments has been performed to study how the introduction of a electrolyte Sodium chloride NaCl to surfactant Hexadecyl trimethyl ammonium Bromide CTAB dilute aqueous solution changes the drag reducing characteristics in the flow at low Reynolds numbers in a 10 mm pipe. The results show that adding Sodium chloride NaCl to CTAB surfactant aqueous solutions can significantly enhance the drag reducing effects at lower Reynolds numbers and can little at higher Reynolds numbers, that the enhancing drag-reducing effect by the introduction of NaCl appears only at higher concentrations than the offset concentration of CTAB for drag reduction, and that the effects increase with increasing concentration of CTAB and of NaCl concentration, but it becomes non-significant, as CTAB concentration is higher than 0.08%. By adding 0.6% NaCl into the 0.02% CTAB aqueous solution flows, the drag reducing rate is increased from 12% without NaCl to 26%, at a Reynolds number of 8 500.

Key words: enhancement of drag reduction, low Reynolds numbers, surfactant, NaCl