Regime, Complete Wetting

In this case, according to Equation 4.94, the pressure inside the spreading drop can be written as 

This expression should be substituted into Equation 4.91, which yields the time evolution of the drop profile, h(t, r)  

Note that the omission of the action of surface forces results in the weU-known singularity on the moving three-phase contact line (see Section 3.1). 

Substitution of the similarity coordinate and function using Equation A2.1 and Equation A2.3 into Equation A2.5 results in 

Equation A2.6 should depend on the similarity coordinate only, and it should not include any time dependence. This is possible only if, simultaneously, the following two relations are satisfied 

---

From the point of view of thermodynamic equilibrium, complete and partial wetting are two distinct equilibrium regimes. Complete wetting means that the contact angle between a liquid and a flat solid surface is zero ( e = 0, see Figure 7.1(c)). In this case, the liquid forms a very thin film on the solid surface and the long-range character of the molecular interactions must be taken into account (10, 12, 13, 17, 18). 

Figure 3.45 Trickle-flow regime with liquid rivulets (complete wetting of the outer surface of the particle).

Fig. 20.a Results of the Cahn construction performed for the segregation data [16] of Fig. 19. Composition derivatives of bare surface free energy (-dfs/d( ))s calculated for different temperatures (symbols A, , O, and for T=99,142,165, and 184 °C, respectively) are fitted well by dashed lines, generated by the function (pf+g /ll+Y s). The hatched area marks the surface energy difference -Afs. b Surface energy derivatives (—dfs/d( >)s (dashed lines) and trajectories -2kV< ) (solid lines) plotted for T=99 °C and 184 °C. For T= 184 °C the surface boundary condition (Eq. 26) is met at point at ( >s>( >2, indicating complete wetting regime. If (—dfs/d([ )s was independent of temperature (and equal to that found at 184 °C) then the boundary condition (O) at 99 °C would correspond to partial wetting (c >s<( >2). In practice, however, (—dfs/d([ )s varies with temperature and the real boundary condition at 99 °C ( ) indicates complete wetting again...

In the complete wetting regime, the relaxation rate of the elementary excitations of the degree of order exhibits a linear critical temperature dependence typical for soft modes. The slowdown of the relaxation rates of the... 

The Yotmg-Lippmann equation has been experimentally fotmd to hold only at relatively lower voltages. In fact, before a probable voltage-induced transition to a complete wetting state (6 = 0) becomes possible, the contact angle tends to get saturated within a certain operating regime. The mechanisms that have been proposed by various researchers to explain this phenomenon are as follows ... 

When a water drop is placed down on very clean glass, it spreads completely. By contrast, the same drop deposited on a sheet of plastic remains stuck in place. The conclusion is that there exist two regimes of wetting depicted in Figure 1.13. The parameter that distinguishes them is the so-called spreading parameter S, which measures the difference between the surface energy (per unit area) of the substrate when dry and wet ... 

FIG. 5 Situation corresponding to the complete wetting regime in which the liquid phase intrudes between the substrate and vapor phase. 

Antonow discovered this rule empirically after measuring the surface tensions of different three-phase systems. At the time, Antonow s rule was the subject of intense scrutiny in the literature partly because Antonow claimed the validity of the rule in any three-phase system with deviations being caused only by supposed nonequilibrium effects [23], We now know that the rule holds exactly, but only in the complete wetting regime. 

Regime of forced convective boiling with complete wetting of the inner tube surface ... 

Berner and Kalis [245] proceed from the expressions for the film thickness in laminar and turbulent regime and the assumption fm- complete wetting, or a constant wetted area independent of the liquid flow rate, and obtained the equations ... 

In general, increases in vapor load and mass velocity increase the severity of high-temperature sulfidic corrosion by crude oils and atmospheric residuum (reduced crude). Corrosion is least severe with flow regimes in which the metal surface is completely wetted with a substantial hquid hydrocarbon layer. Corrosion is most severe with the spray flow that results from vapor velocities above... 

The form of an adsorption isotherm on a geometrically flat substrate in the thick film regime can be described by the so called Frenkel-Halsey-Hill (FHH) theory, under the eussumption of complete wetting of the surface by the film (ref. 4). The FHH vapor pressure is of the form ... 

---