Vortex-assisted molten metal flow: A numerical investigation of air-aspiration suppression through sprue design

• A vortex-assisted flow-gating system was designed to suppress air aspiration and conditions associated with bifilm formation during gravity sand casting. • CFD simulations (ProCAST) demonstrated sustained metal–wall adhesion in the sprue, suppressing initial splash and air pocket formation in simulations. • Near-critical gate velocities (≤0.332 m s −1 ) were numerically achieved by optimizing unpressurized gating ratios from 1:2:4 to 1:2.4:6.1. • Circular runners with continuous tapering enabled balanced multi-gate filling while minimizing turbulence, back-pressure, and sand erosion. Minimizing air entrainment during mold filling remains a critical challenge in gravity sand casting, as uncontrolled free-surface turbulence often leads to casting defects. In this study, a 3D numerical framework is developed to systematically investigate vortex-assisted melt flow as a strategy for suppressing air aspiration during pouring. Extending the qualitative concepts originally proposed by Campbell, this work provides a physics-based computational analysis of vortex formation, melt–wall interaction, and velocity regulation within a multi-gated runner system. Parametric computational fluid dynamics (CFD) simulations were performed using ProCAST for A356 aluminum alloy, with gating ratios varied from 1:2:4 to 1:2.4:6.1 to promote stable vortex formation, uniform gate flow distribution, and near-critical gate velocities (≤ 0.332 m s −1 ). The simulation results demonstrate continuous metal–wall contact along the sprue, effective suppression of initial splashing, and a significant reduction in low-pressure zones associated with air pocket formation. Although the vortex-assisted design necessitates increased runner and gate cross-sectional areas, leading to reduced casting yield, the improved flow stability markedly decreases conditions conducive to air entrainment. This study establishes a computational design framework for vortex-controlled gating systems and provides guidance for future targeted experimental validation and industrial implementation.