Stabilizing the Advancing Front of Thermally Driven Climbing Films

Area of Science:

• Thermodynamics
• Fluid Dynamics
• Surface Science

Background:

• Surface tension decreases with increasing temperature, driving liquid film movement.
• Temperature gradients on vertical substrates can induce upward liquid film flow.
• Previous studies indicated instabilities in thin climbing films.

Purpose of the Study:

• Investigate the stability of thicker, gravitationally draining liquid films.
• Determine conditions for stable film spreading versus rim formation and breakup.
• Validate numerical predictions against experimental data.

Main Methods:

• Linear stability analysis for thin films.
• Numerical simulations for thicker films considering gravitational drainage.
• Comparison of predictions with Ludviksson and Lightfoot's experiments.

Main Results:

• Thicker films with significant drainage spread stably without capillary rims.
• Gravitational drainage promotes a straight advancing front and uniform surface coverage.
• Numerical predictions align well with experimental observations of climbing film behavior.

Conclusions:

• Thicker films experiencing gravitational drainage are inherently stable.
• Eliminating the capillary rim, potentially via counterflow, stabilizes thermally driven films.
• This stabilization technique is applicable to various geometries.