Vane geometry

Commonly, the thickening of liquids by hydrophilic silica is explained by the formation of H-bonds between the silanol groups of silica particles [6]. According to this model, the stability of silica gels in styrene and toluene, two fluids with comparable dielectrical properties, should be more or less identical. Figure 2 depicts the shear yield-stress experiments using the vane geometry of HDK N20 in styrene and toluene. 

Figure 6.15 Concentric cylinder, parallel plate and vane geometries...

Filkova, I. and Weberschinke, J., Effect of vane geometry on droplet size and size distribution in spray dryer, Drying 80, Vol. 2, A.S. Mujumdar, ed., Hemisphere, New York, 1980. 

Fig. 10.5 High-pressure attachment for the rheometer, consisting of a magnetic coupiing, a pressure head, a rotating vane geometry, and a cup. (Reprinted with permission from industriai and Engineering Chemistry Research, Voi. 42(25), N.M.B. Fiichy,...

Figure 1 Flow curve of molten chocolate measured in a vane geometry to eliminate slip.

Theoretical analyses of this geometry has been carried out by several workers who all essentially concluded that for yield-stress/very-shear-thinning liquids, the vane geometry acted as a circumscribing cylinder defined by the tips of the vane blades, with the material inside the virtual cylinder essentially acting as a solid body, and the material outside being sheared in the normal way [1]. This ensures that slip is completely overcome at the rotating member. 

The vane viscometer is yet another form of the concentric cylinder instrument, in which the bob is replaced by a rotor with four blades or vanes each attached by one edge to a vertical shaft, at 90° intervals around the shaft (Figure 22.7). This geometry, which can be used either with a cup or in the infinite sample mode, is particularly useful for measuring yield stress, and can also be used to measure the rheological properties of non-Newtonian liquids. Its advantages are described by Gunasekaran and Ak (2002). 

From numerical simulation of flow of power law fluids in a narrow-gap vane-in-cup geometry (r = 8.5 mm, r = 9.5 mm), Bames and Camali (1990) suggested that for shear-thinning fluids with the flow behavior index <0.5, the fluid within... 

Barnes, H. A. and Camali, J. O. 1990. The vane-in-cup as a novel rheometer geometry for shear thinning and thixotropic materials. J. Rheol. 34 841-865. 

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