Anomaly of pressure drops of rod-like micelle surfactant solutions passing through small orifices

The flow properties of water and surfactant solutions mixed with counter ions were investigated in flows through small orifices. Good agreement between the resultant pressure drops of water and the numerical predictions of the Navier-Stokes equations was obtained. Compared with those of water, the pressure drops of surfactant solutions were larger for molar concentration ratios of 1.0. Moreover, an anomalous flow pattern was observed in the flows through a slot channel: an unstable vortex and unsteady flow were found before the slot for a molar concentration ratio of 1.0, whereas a steady flow pattern was observed for a molar concentration ratio of 10.0. Thus, we conclude that the anomalous pressure drops for surfactant solutions were caused by the unsteady flows.