Leveling a capillary ridge generated by substrate geometry

The formation of capillary ridges is typical of thin viscous films flowing over a topographical feature. This process is studied by using a two-dimensional model describing the slow motion of a thin viscous nonisothermal liquid film flowing over complex topography. The model is based on the Navier–Stokes equations in the Oberbeck–Boussinesq approximation. The density, surface tension, and viscosity of the liquid are linear functions of temperature. For a nonisothermal flow over a planar substrate with a local heater, the influence of the heater on the free surface is analyzed numerically depending on the buoyancy effect, Marangoni stresses, and variable viscosity. The analysis shows that the film can create its own ridges or valleys depending on the heater and the dominating liquid properties. It is shown that the capillary ridges generated by the substrate features can be optimally leveled by using various types of heaters consistent with the dominating liquid properties. Numerical results for model problems are presented.