The effect of a hydrocarbon phase and the presence of a model inhibitor (quat) on local wall shear stresses in the slug flow regime (Fr 5 to Fr 13) was electrochemically quantified with microelectrodes. With a high sensitivity, high frequency current noise data aquisition (up to 200 kHz) high frequency interactions of near-wall slug turbulence elements in the 1 to 6 kHz range were observed which increase in frequency with increasing Froude number. In hydrocarbon- and inhibitor-free aqueous media local wall shear stresses at the time of highest interaction of slug turbulences with the wall are higher by a factor 4 to 5 than corresponding average wall shear stresses. An additional hydrocarbon phase can
reduce the level of average and peak wall shear stresses to some extent. However, real drag reduction can be achieved by adding corrosion inhibitors, e.g. tetradecyltrimethylammonium bromide (TDTMB).
Addition of 0.1 mM TDTMB reduces the slug related peak wall shear stress gradients by a factor of 10 to 20 with respect to the hydrocarbon-free aqueous system. Additionally the amplitudes of high
l~equency interactions of near-wall turbulence elements with the wall are damped significantly in the presence of a hydrocarbon phase and corrosion inhibitor.