Application of the electrodiffusion method to measure wall shear stress: Integrating theory and practice

Abstract

The electrodiffusion method has been used in fluid dynamic research for the past 50years. It allows the measurement of wall shear stress, a crucial parameter, e.g., for the cleaning of membrane modules used in water filtration. Various authors have published articles dealing with the theory behind this technique. But no paper collects all the knowledge assembled over five decades of application. Here, comprehensive summary of the theory of steady flow, unsteady flow, and transient voltage step experiments is given. Factors influencing the accuracy of the measurements are discussed. Furthermore, a new approach to calibrate the system from voltage step experiments is introduced, and practical issues related to its application in flow measurements are discussed for an exemplary signal response to a near-wall flow. The electrodiffusion method (EDM) enables the measurement of wall shear stress. A comprehensive summary of the theory for steady flow, unsteady flow, and transient voltage step experiments is provided and a new approach to calibrate the system from voltage step experiments is introduced. Practical issues related to the application of the EDM in flow measurements are discussed for an exemplary signal response to a near-wall flow. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.