The use of grain refiners plays a crucial role in the casting of Al alloys, and ultrasonic treatment is increasingly applied. This paper focuses on the numerical simulations of 2219, an Al–Cu alloy, using different processes for introducing Al–5Ti–1B grain refiner, along with mechanical stirring and ultrasonic treatment. The multiphase Computational Fluid Dynamics (CFD) model considers turbulent fluid flow, heat transfer, solidification, and the complex interaction between the 2219 Al alloy and TiB2 particles. Ansys's fluent dense discrete phase model (DDPM) and a particle engulfment and pushing (PEP) model are utilized for this purpose. The study investigates the fluid flow patterns and the distribution of TiB2 particles. Additionally, four control experiments are designed to correspond with the numerical simulations, enabling the investigation of the variations in α-Al grains and Al2Cu precipitation phases. The findings demonstrate that direct introduction of Al–5Ti–1B into the ultrasonic sonotrode results in uniform dispersion of TiB2 particles in the Al melt, reduction in α-Al grain size, and decreased area fraction of Al2Cu precipitated phase. The numerical simulation results are successfully validated through experimentation. Al–5Ti–1B ultrasonic sonotrode along with ultrasonic treatment has a good effect on 2219 Al alloy. [ABSTRACT FROM AUTHOR]