A multiscale transient compressible approach for accelerated simulation and optimization of airflow in high-pressure die casting venting elements

High-pressure die casting (HPDC) is a critical manufacturing process for producing complex metal components at high speeds and pressures, where efficient venting is essential to avoid gas entrapment and ensure high product quality. However, simulating airflows in venting elements with full 3D unsteady compressible solvers requires extremely fine meshes, timesteps, and substantial computational resources, with single simulations often taking days or even weeks to complete. This paper introduces and validates a novel multiscale simulation framework that significantly reduces computational cost while preserving predictive accuracy. The approach couples 0D transient models for the die cavity and vacuum tank, 1D transient models for the gas pipelines, and localized 3D compressible simulations for the venting element. Validation against experimental pressure measurements at the vent inlet and outlet confirms very good agreement across different vent geometries and tank sizes. Successive mesh customization and the integration of adaptive time-stepping (ATS) further accelerate the simulations, achieving a final relative speedup factor of nearly 155 compared to the baseline full 3D model. The final multiscale ATS simulation can be completed in a few hours on a conventional PC, making it highly suitable for rapid design iteration and optimization of venting elements. By enabling simulation-driven design, the proposed framework offers a practical pathway to reduce development costs, minimize tests relying on expensive prototypes, and enhance efficiency and quality in HPDC production.