The Use of Electrochemical Techniques to Study Turbulence Close to a Wall

Electrochemical techniques can be used to measure the time averaged velocity gradient and the two components of the fluctuating velocity gradient at a solid surface. A chemical reaction Is carried out at the surface of a small electrode embedded in the wall. The voltage applied to the electrode Is large enough that the current flowing in the circuit is controlled by the mass transfer rate. The probes are the mass transfer analog of the hot wire or hot film anemometer. If the test electrode is part of a large electrode surface, it can be used to measure local time averaged and fluctuating mass transfer rates. Research work on the development of these techniques is reviewed. This includes problems encountered, probe design and mathematical analysis. A typical flow system in which the techniques have been used Is discussed. Data that have been obtained for turbulence close to a wall are presented. A comparison between electrochemical techniques and the thermal wall meters is given