A computational study on droplet impingement onto a thin liquid film

الملخص EN

The impingement of a droplet onto a thin liquid film is studied by numerical simulation.

The Navier–Stokes equations for unsteady, incompressible, viscous fluids in the axisymmetric coordinate system are solved using a control volume method.

The volume-of-fluid (VOF) technique is used to track the free-surface of the liquid.

Model predictions are in good agreement with experimental measurements.

It is found that the dynamic processes after impact are sensitive to the initial droplet velocity and the liquid pool depth.

The time evolution of the crown height and diameter are obtained by numerical simulation.

The maximum crown height and its corresponding time are calculated using the model for different We (Weber) numbers and various film thicknesses.

Results show that the non-dimensional film thickness has a small effect on the non-dimensional parameters related to the maximum crown height and its corresponding time.

Next, the critical we number for splashing (Wecr) is studied for Oh (Ohnesorge) numbers in the range of 0.01~0.1; the results compare well with those of the experiments.

The numerical simulation is also performed for lower Oh (Oh~0.001) where experiments cannot be performed due to limitations in the instruments.

The critical we number is found to be insensitive to the non-dimensional film thickness; it decreases, however, with decreasing Oh number or liquid viscosity.

Finally, simple expressions are developed that correlate the non-dimensional parameters involved in the droplet impingement onto a thin liquid film.