Estimating the flow dynamics from instantaneous wall heat transfer in an impinging sweeping jet

Despite recent advances in impinging sweeping jets, it remains unclear whether a linearcorrelation between momentum and heat transfer holds locally across the impingementregion, and whether this coupling permits the temporal reconstruction of the dominantvelocity dynamics solely from wall measurements. This study investigates whether theunsteady velocity dynamics of an impinging sweeping jet can be inferred from non-intrusivewall heat-transfer measurements. The flow is characterised by strong spatial inhomogeneityand large-scale, aperiodic motion associated with the sweeping dynamics. Particle ImageVelocimetry snapshots are combined with time-resolved convective heat-transfer fieldsacquired on the impingement surface, modelled with a heat-flux sensor and measured usinghigh-speed infrared thermography. We use Extended Proper Orthogonal Decomposition asa reduced-order linear correlation framework to assess and exploit the temporal couplingbetween wall thermal signatures and the impinging velocity field measured on orthogonalplanes. The method successfully enriches the temporal description of the large-scale velocitydynamics. These findings indicate that the primary energy-carrying structures of the floware encoded in the wall heat-transfer dynamics. The modal analysis provides evidence of alow-rank linear coupling between wall heat transfer and the dominant velocity dynamics inthis configuration.