Effect of contact angle

It is not common practice to measure the contact angle and, indeed, there is some evidence that its value is affected by surface roughness. The hysteresis encountered in mercury porosimetry may be completely removed by the use of different contact angles for intrasion and extrusion. On this basis the use of hysteresis to predict pore shape may lead to erroneous and misleading data. 

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Fig. Xm-3. Effect of contact angle in determining water repellency of fabrics.

Barajas AM, Panton RL (1993) The effect of contact angle on two-phase flow in capillary tubes. Int J Multiphase Flow 19 337-346... 

Fergusoni discussed the possible effect of contact angle. Rebenstorff noticed that when a drop is formed, a small secondary drop follows the main drop. 

Tabic 2.4 Effect of contact angle of heterogeneities (2 x lo cm ) on calculated critical cooling rates (K.s ) for glass formation. (After Onarato and Uhlmann, 1976)... 

FIGURE 8-4 Effect of contact angle on emulsion type. 

FIGURE 10.22 Capillary phenomena, (a) Rise of liquid in a capillary if the contact angle 0 = 0 (perfect wetting), p is pressure, y is surface tension, p is mass density, and g — 9.81 m s-2. (b, c) Effect of contact angle. 

FIGURE 15.37 Effect of contact angle on heat transfer coefficient in nucleate pool boiling with a constant heat flux and subcooling (from Jansen et al. [77], with permission from ASME). 

Fig. 7. Experimental effect of contact angle (water) on a fluorinated wax as a function of surface roughness (Ref )...

Rosengarten G, Hairie D, Cooper-White J (2005) Using computational fluid dynamics to study the effect of contact angle on microdroplet deformation. ANZIAM J 46 C304-C319... 

L Solid-Liquid-Fluid Systems The Effect of Contact Angle... 

Complete analysis of the effect of contact angle on a given system is complicated (naturally) by the possible existence of hysteresis, roughness effects, and surface compositional variations within the fibers. If a > 90° for a given liquid, it will not spontaneously enter into the fiber network under the drive of capillary forces. Likewise, if 0r is also > 90°, any liquid forced into the network by external physical forces will be spontaneously expelled from the system. Such a situation represents the ideal for most effective repellency control. Even if those conditions cannot be achieved, however, large values of 0A < 90° will at least retard entrance of liquid into the fiber matrix or maintain a slow rate of movement. 

A mathematical model which can predict mobilization of entrapped ganglia under the influence of both gravity and flow has been recently developed (8). The work, which was based on suitable force balances and included the effects of contact angle, was supported by measurements performed using a fluid-fluid-solid system and a simple cubic geometry. This model differed from that of Ng et al., in that their analysis of blob movement was semi-quanti-tative for what was assumed to be a uniformly wetted system (13). Ganglion mobilization experiments which included various intrinsic or smooth surface contact angles were conducted by Morrow, but were not quantitatively assessed (9). 

G. Roserrgarten, J. Cooper-White, G. Metcalfe, Experimental and analytical study of the effect of contact angle on liquid convective heat transfer in microcharmels, Int. J. Heat Mass Transfer. 2006, 19, 4161-4170. 

Figure 7. This illustrates the effect of contact angle on imbibition capillary pressures for air/liquid in Teflon cores. 9e is the contact angle on a smooth flat plate and 0 is the advancing contact angle on a roughened Teflon surface. is the displacement curvature Pi i, is the imbibition capillary pressure o is the surface tension. (Reproduced by permission from reference 103. Copyright 1978.)...

Figure 5.11 Effect of contact angle on the equilibrium force of particles with radii = L. ...

When the column of liquid has reached the same equilibrium position from either a lower or a higher height. (The effect of contact angle hysteresis may make these two heights slightly different.)... 

Ishino C, Okumura K. (2006) Nucleation scenarios for wetting transition on textured surfaces The effect of contact angle hysteresis. Europhys Lett76 464 70. 

Example 15.1. Effect of contact angle measurements on the determination of solid surface tensions using the Owens-Wendt method. Based on data by Owens and Wendt (1969). 

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