Generalized theory for wall shear stress measurement using circular-segment electrodiffusion probes

Studying turbulent boundary layers using experimental measurement techniques remains a challenging task even today. The area in the immediate vicinity of a solid surface, known as the laminar sublayer, presents a particular challenge. The method must primarily enable obtaining local values of the studied quantities while maintaining a non-invasive character. Understanding these processes has numerous applications – from designing more efficient mixing devices in the chemical industry, to producing more efficient heat exchangers, and to designing aircraft and ships.

Our Research Group of Multiphase Reactors has a long tradition of using the electrodiffusion method. This method enables the description of the hydrodynamics within the laminar sublayer, making it an ideal candidate for a deeper understanding of the boundary layer’s nature. This study aims to generalize the shape of the commonly used twin semicircular measuring probe. The main contribution is the design of new measuring probes, where the individual segments have a circular-segment shape. This enables more sensitive diagnostics of local changes in the direction of fluid flow. Thanks to the derived analytical relations for evaluating experimental data, the applicability of the electrodiffusion method is expanded, and its ability to describe more complex flow structures is further enhanced.

The published theory, therefore, provides new and remarkable insights into the study of transport phenomena near walls, opening the way to a more precise understanding of turbulent processes in this critical region.

• Harrandt V., Bazaikin Y., Huchet F., Tihon J., Havlica J.*: Generalized theory for wall shear stress measurement using circular-segment electrodiffusion probes. Commun. Heat Mass Transf. 2025, 167B(Sept 2025), 109322. doi.org/10.1016/j.icheatmasstransfer.2025.109322