Active control of turbulent drag reduction in surfactant solutions by wall heating

Flow characteristics of surfactant solutions have been experimentally investigated in order to see the possibility to actively control drag reduction by wall heating. Rheological measurements of drag reducing surfactant solutions were made to examine thermal effects of the fluid properties. The surfactant used was Cetyltrimethyl ammonium chloride (CTAC), a cationic surfactant. It was found that a drastic decrease of apparent viscosity appears at a micellar shape transition temperature. This characteristic implies the possibility of controlling drag reducing flow through heating. A plane two dimensional channel equipped with a wall heater element was employed and LDV measurements were made to estimate the heating effect on the flow field. Two components of turbulent fluctuation intensity, u' and v' and Reynolds shear stress are presented. Based on this, modification of turbulence features by heating are discussed.