Flow over a Flat Plate in Surfactant Solutions

Abstract

The effect of surfactant solutions on the flow over a flat plate has been investigated by measuring the velocity profiles in the Reynolds number range of 1.1×10^5 < Re < 4.5×10^5. Surfactant solutions were aqueous solutions of oleyl-bihydroxyethyl methyl ammonium chloride (trade name: Ethoquad O/12) in the concentration range of 50 to 200 ppm, to which sodium salicylate was added as a counterion. It was clarified that the boundary layer thickness of surfactant solutions increases significantly comparing with that of tap water at Re < 3×10^5. Velocity profile of the boundary layer for surfactant solutions gradually increases from the outer edge of the boundary, and approaches the turbulent velocity profile of Newtonian fluid. The shape factor with surfactant solutions has a constant value of 1.7 < H < 2, and transition to turbulent is not appeared clearly.