Numerical and Experimental Investigation of Dynamic Air-Assisted Spray Deposition Characteristics on Horn-Shaped Surface

To address the challenge of uneven coating deposition during air-assisted robotic spraying on horn-shaped surfaces, a gas–liquid coupled numerical model based on the Euler-Euler multiphase flow approach was developed and experimentally validated. Two dynamic spray trajectories (axial spraying and circumferential spraying) were designed to investigate the effects of spraying strategy, horn angle (45°–135°), spray distance, and spraying speed on film-forming characteristics. Results indicate that horn features alter the near-wall flow field through wall confinement effects, causing spray splitting and kinetic energy attenuation with significant anisotropy—stronger geometric constraints along the minor axis and weaker along the major axis. Axial spraying requires approximately 60% less time than circumferential spraying and yields more uniform coatings, making it the preferred strategy. During axial spraying, the central film thickness increases monotonically with horn angle (up to 147.7% over 45°–135°), while circumferential spraying achieves optimal uniformity at 67.5°–90° governed by competing geometric and temporal effects. The film thickness approximately follows a power-law decay with spraying speed (h ∝ 1/v). Pearson correlation analysis identifies horn angle as the primary variable controlling film thickness (r = 0.466), followed by spraying speed (r = −0.347) and spray distance (r = −0.325), with an optimal spray distance of 190–210 mm recommended. This study reveals the anisotropic regulation mechanism of horn features on the spray flow field and provides quantitative guidance for precise robotic spraying of complex-curved components.