Direct numerical simulation of droplet impact onto dry stationary and moving walls at low to high Weber numbers

Abstract

The accurate prediction of the drop–wall impact dynamics and regime are of interest in many engineering applications. Considerable progress has been made in different elements of Direct Numerical Simulation (DNS) approaches. However, identifying the optimal combination of improved submodels that perform well under a wide range of operating conditions, covering low to high Weber numbers with varying surface wettabilities and wall motions, still requires further investigation. Here, we conduct a comparative study on the performance of key DNS elements, including the Interface Tracking (IT) algorithm for the widely-used volume-of-fluid approach, Contact Angle (CA), Contact-Line Velocity (CLV), Instability Actuation (IA), and numerical discretization. The study spans a broad range of Weber numbers, encompassing various impact phenomena such as drop oscillation, partial rebound, fingering, and splash. It is concluded that the Kistler CA model provides the most accurate predictions among the models considered here. In terms of IT, the Multidimensional Universal Limiter with Explicit Solution (MULES) algorithm is the most efficient one, especially for moderate to high Weber numbers. For high Weber numbers, involving the fingering instability and splash events, while applying the IA mechanism slightly improves the results, using a high-quality fine-enough grid and appropriate numerical discretization scheme to control the dispersion and dissipation errors are more important ingredients. It is shown that the recommended model combination is also able to predict the important features of drop impact on moving walls with reasonable accuracy.