LES of Droplet Impingement: Application to Clean and Laser-Scanned Ice Shapes

TL;DR

This study uses high-fidelity simulations to analyze droplet impingement on ice shapes, revealing how surface roughness influences local droplet distribution and ice accretion patterns, explaining characteristic ice structures.

Contribution

It introduces a validated computational framework to quantify the effects of surface roughness on droplet impingement and ice growth, advancing understanding of ice roughening mechanisms.

Findings

Physical roughness causes nonuniform droplet impingement with concentrated upstream impacts.

Smooth surfaces suppress localized impingement peaks, reducing roughness amplification.

Localized impingement promotes self-reinforcing roughness growth over time.

Abstract

The prediction of aircraft icing is conventionally performed using multishot simulation frameworks that fail to predict the progressive roughening of the ice surface. To understand roughness formation, we investigate droplet impingement on clean and laser-scanned rough ice shapes using a high-fidelity computational framework based on wall-modeled large-eddy simulations and Lagrangian particle tracking. This methodology is validated against experimental data for a NACA 23012 airfoil and a NACA 64A008 swept tail, accurately predicting collection efficiency and supercooled large droplet splashing. The framework is subsequently applied to laser-scanned rime ice geometries to quantify the impact of surface roughness on local impingement distributions. The results reveal that physical roughness induces a highly nonuniform collection efficiency, with droplet impingement intensely concentrated on upstream-faces of roughness elements, creating sheltered shadow zones immediately downstream. While the spanwise-averaged collection efficiency remains remarkably similar to that of an equivalent smooth body, idealized smooth surfaces completely suppress these localized impingement peaks. Ice accretion simulations demonstrate that this localized impingement creates a self-reinforcing feedback loop, actively amplifying existing roughness features over time. These findings provide a direct physical explanation for the formation of characteristic rime ice structures and highlight the critical role of local surface topology in the accretion process.