Constricted Surface Geometries

5 Experimental Studies of the Liquid Structure at Solid-Liquid Interfaces 

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The second equation is the bulk effective resistivity due to particle surface resistivity for a cubic array of mono-dispersed particles with the direction of the electric field aligned with the poles and volume conduction neglected. The constriction resistance is included in the integration of Equations 3.8. These equations are a weak function of the particle geometry. 

Capillary burst valves, which are rotationaUy actuated, stop flow by the counterpressure induced at a capillary feature such as a hydrophobic constriction or a sudden expansion in a (hydrophilic) channel (Fig. 4). If the substrate material is hydrophobic, the valve is typically formed by a constriction in the microchannel. These burst valves yield once the spin rate passed a certain threshold governed by the valve geometry, its radial position, the contact angle, and the surface tension of the liquid. Mainly due to minimum feature sizes and manufacturing tolerances, there is a practical limit which, on the one hand, restricts the maximum burst frequency and, on the other hand, smears out the definition of the nominally discrete burst frequencies into bands. In many applications the number of independently controllable burst valves and thus the number and vigorousness of LUOs are significantly capped [4]. 

Erosion of the outer surface of the gas outlet tube or vortex finder can occur from several possible causes and we will briefly discuss each of these below. Perhaps the most obvious cause is direct impaction, which can occur if any part of the vortex finder lies in the projected path of the particles entering the cyclone. See Fig. 12.1.3a. As shown in Fig. 12.1.3b, the incoming gas can be expected to constrict, either due to the geometry or due to the effect of the gas already rotating in the cyclone and flow around the gas outlet tube. But this is not always the case for the solids. 

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