WSS in a rotor stator mixer

Mixing head of the Arde Barinco reversible mixer with sensor attached to the cylindrical stator element. Inset shows the head with the stator removed, revealing the impeller blades.

Arde Barinco Reversible Homogenizing Laboratory Mixer

Tests were carried out with RealShear™ F-400 and F-8K shear stress sensors to measure the shear stress at the inner wall of the stator in a CJ-4E Arde Barinco reversible homogenizing mixer. This kind of mixer can be set for either downward flow or upward flow into a baffle plate. The sensor was attached to the stator with a custom 1/4”-80 threaded hole (see photos) such that the sensor face was flush with the inner wall of the stator with a small gap separating it from the blades of the impeller. Presented are plots of the time-dependent shear stress signal (in glycerol) showing the ability of the sensor to resolve individual passes of the impeller blades. Data such as this can be used to ensure proper processing or evaluate new mixer designs.

Shear stress signal as mixer is turned on and off.
Shear stress signal for steady state operation. The peaks in the signal represent moments when the impeller blade passes by the sensor face.
Close-up of the shear stress signal as the mixer is turned on. The increasing frequency of the impeller rotation can be seen.
Close-up of the shear stress signal as the mixer is turned off.

Below are plots of the dependence of shear stress on the rotational rate of the impeller for both glycerol (Newtonian) and shampoo (shear-thinning).

Close-up of the shear stress signal as the mixer is turned on. The increasing frequency of the impeller rotation can be seen.
Shear stress versus RPM for shampoo in the reversible mixer. Positive values of RPM indicate upward flow and vice versa.