4 research outputs found
Spreading with evaporation and condensation in one-component fluids
We investigate the dynamics of spreading of a small liquid droplet in gas in
a one-component simple fluid, where the temperature is inhomogeneous around
0.9Tc and latent heat is released or generated at the interface upon
evaporation or condensation (with Tc being the critical temperature). In the
scheme of the dynamic van der Waals theory, the hydrodynamic equations
containing the gradient stress are solved in the axisymmetric geometry. We
assume that the substrate has a finite thickness and its temperature obeys the
thermal diffusion equation. A precursor film then spreads ahead of the bulk
droplet itself in the complete wetting condition. Cooling the substrate
enhances condensation of gas onto the advancing film, which mostly takes place
near the film edge and can be the dominant mechanism of the film growth in a
late stage. The generated latent heat produces a temperature peak or a hot spot
in the gas region near the film edge. On the other hand, heating the substrate
induces evaporation all over the interface. For weak heating, a steady-state
circular thin film can be formed on the substrate. For stronger heating,
evaporation dominates over condensation, leading to eventual disappearance of
the liquid region.Comment: 12 pages, 14 figure
Pre-dewetting transition on a hydrophobic wall: Statics and dynamics
For one-component fluids, we predict a pre-dewetting phase transition between
a thin and thick low-density layer in liquid on a wall repelling the fluid.
This is the case of a hydrophobic wall for water. A pre-dewetting line starts
from the coexistence curve and ends at a surface critical point in the phase
diagram. We calculate this line numerically using the van der Waals model and
analytically using the free energy expansion up to the quartic order. We also
examine the pre-dewetting dynamics of a layer created on a hydrophobic spot on
a heterogeneous wall. It is from a thin to thick layer during decompression and
from a thick to thin layer during compression. Upon the transition, a liquid
region above the film is cooled for decompression and heated for compression
due to latent heat convection and a small pressure pulse is emitted from the
film into the liquid.Comment: 14 pages, 17 figure
Wetting dynamics with evaporation and condensation(Poster session 1, New Frontiers in Colloidal Physics : A Bridge between Micro- and Macroscopic Concepts in Soft Matter)
この論文は国立情報学研究所の電子図書館事業により電子化されました。我々はdynamic van der Waal理論[1]を用いて、蒸発と液化を伴う流体の濡れをシミュレーションによって調べた。その結果、気・液・固の接触線付近では特に蒸発・液化が激しくなっていることがわかった。また、床との長距離相互作用としてvan der Waals力を考慮に入れたときの液滴の濡れ方についても調べた