Experimental Investigation of a Planar Liquid Film Atomization Under High-Speed Gas Stream

We present a systematic experimental investigation of the primary breakup of a planar liquid film subjected to high-speed co-flowing gas streams. A water film of thickness Dℓ ≈ 150 μm is produced from a symmetric airfoil lip and sheared on both sides by compressed air. Interfacial dynamics were recorded with a high-speed camera and analyzed to extract transverse wavelengths, rupture modes, and their dependence on operating conditions. We find that the transverse wavelength λtra decreases strongly with increasing gas speed and that, for a given dynamic pressure ratio M = (ρgV2g )/(ρℓV2ℓ ), different absolute combinations of Vg and Vl produce markedly different λtra. These observations indicate that gas-shear intensity and the gas flow instability modes (vortex shedding) control the breakup of the liquid film; the liquid inflow plays a secondary role under our conditions. The results provide experimental benchmarks for model validation and suggest routes to tune atomizer performance via gas-side control.