Numerical simulation of isothermal nonwetting

Abstract

SUMMARYA numerical simulation of isothermal wetting suppression in the presence of shear is considered during which wetting may be prevented when a drop approaches a moving wall. Air is driven into the passage between the solid and liquid surfaces by viscous action, preventing wetting. Silicone-oil and water drops are investigated for different wall velocities and wall distances. The droplet dimples at the upstream side and bulges at the downstream side when nonwetting occurs. The free-surface deformation can be enlarged by either increasing the wall velocity or decreasing the wall distance. The low-viscosity silicone-oil used in these calculations is much more sensitive to shear wetting suppression than is water, because the Weber number of the silicone-oil is larger than that of water.

Multiscale modelling in the numerical computation of isothermal non-wetting

“…Streamlines for the flow field from the FIDAP model by Kuo et al (2005) are shown in figure 3(b). Their computation had the same spacing d = 1.01 and Re = 23.756 (a lower surface speed of U = 300 mm s −1 ).…”

“…Thus, the goal of the present work is to find steady solutions for the flow in the gas and the liquid and the shape of the drop as functions of the solid-surface separation distance d, the flow rate of the gas q, and the Reynolds number Re. The default parameter set used for all results reported in this work are for 4.55 cSt silicone oil and air and a lower-surface translation speed of 30 cm s −1 , corresponding to the simulations of Kuo et al (2005). The material properties are listed in table 1.…”

“…Note that these values for the relaxation parameters may not be optimal and that both forms of relaxation are needed to ensure successful iterations when the separation distance is less than one. Kuo et al (2005), and (c) pressure along the lower surface from the FEMLUB model.…”

“…Although a two-phase lubrication analysis of the type performed by Sumner et al (2003) is also possible for this system, the present work will seek a solution that does not require a flat drop through the use of a hybrid lubrication-theory/computationalfluid-dynamics (CFD) approach. Kuo, Chen & Neitzel (2005) used their FIDAP model to compute full CFD solutions for this case, but could not obtain solutions for extremely thin lubricating films, just as in the thermocapillary non-wetting problem discussed above.…”