Simultaneous wall shear rate measurements by a three segmented electrodiffusion probe and laser-Doppler-anemometry

Abstract

In a fully developed turbulent channel flow, the instantaneous wall shear gradient was measured simultaneously by an electrodiffusion (ED) probe and by laser-Doppler anemometry (LDA). The LDA measurements were done in the viscous sublayer and the linear velocity profile was used to calculate the instantaneous shear gradient at the wall. The electrodiffusion probe requires presence of a suitable electrolyte (e.g. an iodine and potassium-iodine aqueous solution) for reduction of the species on the working electrode (cathode). This results in a concentration gradient of the ions due to the convective diffusion of the [I3]- to the cathode.