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Edge Effects in Rotational Viscometry VI. ZZ- and KK- Type Sensors: No-slip Pseudosimilarity for Inertialess Flow (Revisited)
Wein, Ondřej ; Havlica, Jaromír
This report should serve as a manual to the program Prog_cL_m.exe for calculating the correction cL on edge effects in narrow-gap rotational viscometry with almost cylindrical or conical spindles. Referring to the previous Research Report ICPF 2004/8, which deals with the same subject, it includes, in addition, also computation of cL for the entire ZZ and KK sensors with an arbitrary front of bottom semi-sensors (FLAT, CONE, HUB, HAAKE). Detailed attention is paid to numerical aspects: extrapolation/interpolation of the related fields (angular velocity, shear stress, dissipation, local torque contribution) towards the boundaries, including the analytical smoothing at singularities. The source codes for Prog_cL_m.exe, the results of numerical simulations, as well as the resulting correlations for cL , are available on the attached CD, which is an integral part of this report. The inertia effect was computed using commercial software FLUENT 12 for the Z40DIN sensor and applied in an approximate way also for the KK35/23 sensor.
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AWS Viscosimetry of Microdispersions - Detection of Apparent Wall Slip
Pěnkavová, Věra ; Večeř, M. ; Wein, Ondřej
The rheometric data measured using three various sensor geometries (PP60, ZZ40DIN and KK-sensor) are compared in this contribution at the case of water solution of polymer welan. The KK-sensor, constructed at our department, combines advantages of geometry both plate-plate and concentric cylinder geometry. It is shown that KK-sensor is comparable to commercial sensors. It is presented for water kaolin dispersions that apparent wall slip does not disappeared neither for low consistent dispersions. The values of slip coefficients are even higher in the case of less consistent samples.
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AWS Viscometry – Principles and Applications
Wein, Ondřej
Quantitative identification of Apparent wall slip (AWS) effect, accompanying the flow of colloidal dispersions in confined geometries, requires a specific modification of common viscometric methods. Essential distinction between common and AWS viscometry is outlined – including theoretical background, calibration, data acquisition, and downstream data treatment – and demonstrated for a class of rotational viscometers.
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Effect of Surface Quality in Viscometry of Aqueous Polymer Solutions
Večeř, M. ; Wein, Ondřej
The proposed paper is focused on experimental viscometric study of AWS effect of aqueous polymer solutions: 1.5% wt solution of Na salt of Carboxymethylcellulose, 0.4%wt of Welan Gum and 1% wt of Polyacrylamide was chosen as the tested liquids. Four viscometric sensors (type KK) with different quality of surface (Stainless steel, Titanium, Alloy of Aluminum and Magnesium, as well as Stainless steel with surface roughened by sandblasting) have been used. It is documented that the extent of AWS effect strongly depends both on the sensor material and type of solution.
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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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