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Wall Shear Rate Components for Wavy Taylor-Couette Flow
Kristiawan, M. ; Jirout, T. ; El Faye, A. ; Sobolík, Václav
Experiments were carried out in the wavy flow between concentric cylinders with the inner cylinder rotating and outer cylinder fixed. The radius and aspect ratios were 0.8 and 44, respectively. The electrodiffusion method with a three-segment and simple micro-electrodes was used for study of the axial and azimuthal components of shear rate at the outer cylinder. The axial distributions of these components were obtained by sweeping the vortices along the probes using a slow axial flow. The wavelength and phase celerity of waves, height of vortices and their drifting velocity were calculated from the measured limiting diffusion currents.
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Electrodiffusion Diagnostics of Apparent Wall Slip in Polymer Solutions
Wein, Ondřej ; Tovčigrečko, Valentin ; Večeř, M. ; Sobolík, Václav
Two substantially improved experimental methods, the apparent wall slip (AWS) rotational viscometry with a Morse-taper sensor and electrodiffusion (ED) flow diagnostics with autocalibrated friction probes, are used to study near-to-wall velocity profiles in aqueous solutions of high-molecular polysaccharides under viscometric flow conditions. By comparing the velocity data from the both methods, estimates of the depleted layer thickness in dependence on wall shear stress are obtained. The ED data support the two-layer model of AWS effect, with the constant enhanced fluidity across the depleted layer.
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