Immersed Boundary Methodology for Three-Dimensional Multistep Ice Accretion Simulations

In-flight ice accretion poses a significant risk to aircraft safety and performance. Despite advancements in ice protection systems, aircraft must demonstrate the ability to operate safely under icing conditions, highlighting the importance of reliable ice accretion simulations. Traditional multistep simulations divide the accretion process into discrete stages, improving the accuracy of ice predictions. However, this approach increases computational costs and reduces automation, as evolving ice shapes necessitate the generation of new grids. This paper investigates the application of immersed boundary methods (IBMs) to eliminate the need for volume remeshing, thereby enhancing the automation of multistep simulations. The proposed framework, integrated into the ONERA three-dimensional (3D) icing suite IGLOO3D, uses a ghost-cell method for modeling airflow and a penalization approach for simulating droplet impingement, building upon recent work by the authors. By relying on inviscid flow simulations, the method significantly reduces computational costs; however, boundary-layer calculations are required. To address this, a 3D simplified integral boundary-layer solver based on the resolution of partial differential equations on a surface is presented. Results from three cases of the 1st Ice Prediction Workshop are presented and analyzed, demonstrating the potential of IBMs to enhance the efficiency and practicality of 3D ice accretion simulations.