Patterns and Reduced-Order Reconstruction of Impinging Wiping Jet Pressure Profile Fluctuation Using Proper Orthogonal Decomposition

Wiping jet impingement pressure is important in controlling the coating mass (thickness) and influencing the smoothness of the thin metallic coating produced in continuous galvanizing lines (CGLs). However, the fluctuation of the impingement pressure profile that directly impacts the coating smoothness has not been adequately understood. To study key features of the impingement pressure fluctuation, the instantaneous impingement pressure profiles obtained from large eddy simulations (LES) were analyzed using proper orthogonal decomposition (POD). Dominant fluctuation modes of pressure profiles can be differentiated based on the energy contents of the modes corresponding to different jet types, namely, mixing, nonmixing, and transitional mixing jet. The dominant modes of mixing jets in the wiping region contain comparable strength of all modes (flapping, pulsing, and out-of-phase multipulsing). Nonmixing jets do not show discernable fluctuation modes, and transitional mixing jets show pulsing and flapping modes only. Additionally, instantaneous maximum pressure gradients and their locations were determined from the reduced-order reconstructions of the pressure profiles. From the analysis, frequency spectra of the magnitude and location fluctuations of the maximum pressure gradients associated with each of the jet types can be clearly distinguished. This is the knowledge that may be helpful for CGL operators in the operation of wiping jets.