Influence of liquid column impact wall on liquid film thickness fluctuation outside the horizontal tube

A 3D falling film flow model outside the horizontal tube is established to study the influence of the liquid column impact the wall on the liquid film thickness distribution. It is found that the liquid film thickness fluctuates significantly at 0°–60° in single liquid column, and the minimum thickness appears. In the jet flow, there is a critical value of 70° due to the liquid film fluctuation. The liquid film thickness change before 70° was negatively correlated with Reynolds number and positively correlated after 70°. And the fluctuation amplitude negatively correlates with the Reynolds number.