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 was developed using the Euler–Euler multi-phase flow approach and subsequently validated through experimentation. Two dynamic spray trajectories—axial spraying and circumferential spraying—were designed to examine the influence of spraying strategy, horn angle (ranging from 45° to 135°), spray distance, and spraying speed on film-forming characteristics. The results demonstrate that the features of the horn alter the near-wall flow field due to wall confinement effects, leading to spray splitting and kinetic energy attenuation with pronounced anisotropy. Specifically, stronger geometric constraints are observed along the minor axis, while weaker constraints are noted along the major axis. Axial spraying requires approximately 60% less time than circumferential spraying and results in more uniform coatings, thereby establishing it as the preferred strategy. In axial spraying, film thickness increases steadily with horn angle, with a 147.7% increase from 45° to 135°. Circumferential spraying achieves the best uniformity at angles of 67.5° to 90° due to geometric and temporal influences. Film thickness decreases with spraying speed following a power-law relationship (h ∝ 1/v). Pearson correlation shows moderate links between film thickness and horn angle (r = 0.466), spraying speed (r = −0.347), and spray distance (r = −0.325), with an ideal spray distance of 190–210 mm. The study highlights the anisotropic effects of horn features on spray flow, offering quantitative insights for precise robotic spraying of complex surfaces.