Theory for electrodiffusional wall shear stress measurement by directionally sensitive twin semicircular probe

For a precise understanding of the transport phenomena between a solid wall and a fluid, it is essential to have a detailed description of the hydrodynamic behavior in the immediate vicinity of the surface. The electrodiffusion method offers significant potential in this regard, as it relates measured electric currents to local hydrodynamic properties. This issue from the Research Group of Multiphase Reactors brings a new theoretical framework that extends this method to reliably capture not only the magnitude but also the direction of wall shear stress. The core contribution lies in the derivation of explicit analytical relations for a double semicircular electrodiffusion probe, which directly converts the measured electric currents into detailed information about the boundary layer hydrodynamics, including the challenging laminar sublayers.

The study also proposes a data processing approach that considers both forward and reverse flow conditions, thereby enhancing the practical applicability of the concept. In addition, we conducted a sensitivity analysis of the double semicircular probe, focusing on how the measured current ratios respond to changes in flow direction. This step is critical for accurate interpretation of the results and for identifying potential limitations in future practical applications. Thus, our findings provide a solid basis for designing experimental setups, optimizing probe geometry, and more effectively interpreting measurement data. Overall, this theoretical concept advances the electrodiffusion method towards a more accurate and comprehensive description of near-wall conditions, which is essential for gaining deeper insights into transport processes and applying this knowledge in engineering practice.

• Harrandt V., Bazaikin Y., Huchet F., Tihon J., Havlica J.*: Theory for electrodiffusional wall shear stress measurement by directionally sensitive twin semicircular probe. Int. J. Heat Mass Transf. 2024, 235(15 Dec), 126191. doi.org/10.1016/j.ijheatmasstransfer.2024.126191