Dynamics of direction - specific friction probes for the electrodiffusion diagnostics of flow in rheologically complex liquids

Electrodiffusion (ED) sensors work on the polarographic principle. Depending on the operation mode, they detect either concentration/diffusivity of the depolarizer (oxygen, quinon, triiodide, ferricyanide) or a local kinematics of surrounding liquid. Depending on actual construction, they monitor local velocity (anemometers) or velocity gradient (friction probes). Multi-segment ED friction probes, in addition, monitor also the varying flow direction. Unfortunately, their safe use is still limited to slowly varying flows and to homogeneous liquids. In the suggested project, we intend to improve their function by using our knowledge of the single-segment probe dynamics. The computer-aided calibration and control of multi-segment ED probes would be improved by

(i) including the effect of insulating gaps on dynamics (essential in fast changing flows),

(ii) including the effect of longitudinal diffusion (essential in slow flows, low Peclet numbers),

(iii) including the dynamic (voltage-step) direction-specific calibration of the individual segments and incorporated into a new issue of the software EDWORK. For confirmation of the theory and algorithms, the experiments in a few well-controlled unsteady viscometric flows will cover a variety of biological and polymeric liquids. The related data on diffusivities and viscosities would be an important by-product of the intended research.