Experimental investigation of coherent structures and acoustic properties of a steam jet condensation in crossflow using proper orthogonal decomposition

Direct contact condensation of steam jets in crossflow is crucial for various industrial applications, yet its flow structures and noise mechanisms remain inadequately understood. This study investigated the formation and evolution of multi-scale vortex structures in the turbulent jet flow field, which induce significant sound pressure oscillations and pipe vibrations. Multi-scale coherent structures in typical condensation regimes were extracted via high-speed imaging and proper orthogonal decomposition method. Additionally, acoustic and vibration characteristics were characterized by hydrophones and accelerometers, combining with time-domain and frequency-domain analyses. The intensities of sound pressure oscillation and pipe vibrations, which are highly correlated with the condensation regimes, initially rise before declining with increasing steam mass flux, and steadily rise with subcooled water temperature. Notably, the spectral distributions of sound pressure and vibrations shift toward higher frequencies as steam mass flux increases. In unstable regimes, large-scale coherent structures in low-order, high-energy modes dominate sound pressure oscillations. Conversely, in the Stable regime, sound pressure oscillations are influenced by the interaction between fine-scale vortex structures in high-order modes and shear-layer vortices generated by shear-layer instabilities in low-order modes. These findings enhance our understanding of the coherent structures in the turbulent jet flow field and provide insights for identifying noise sources.