| Pressure sensitive paints (PSP) have been gaining more popularity in experimental fluid mechanics and aerodynamic testing. A major problem with PSP pertains to its temperature dependence making the calibration process very difficult. Dual-luminophor PSP has an added temperature phosphor to provide temperature information for the calibration. Dual-luminophor systems still suffer from the inherent temperature dependence and possess added complications due to spectral cross talk and overlap. However, to date there is no successful universal calibration technique for dual-luminophor systems. Such calibration is needed for dual-luminophor PSP to become a practical experimental tool.; With this aim, a statistical technique known as proper orthogonal decomposition (POD) is used to extract pressure and temperature information from intensity data. POD works by defining and separating the main factors of any system and evaluating the proportional contribution of each factor. The calibration technique is examined by applying the dual-luminophor PSP in a channel flow experiment. Before applying the calibration experimentally, a set of artificial data is examined using POD to provide a fundamental understanding of POD as a calibration technique. The experiment was designed to allow for different flow conditions and temperature gradients to interact, hence providing enough variation to examine the calibration technique. Seven cases are examined, with each case shedding light on a particular aspect of the calibration. The POD calibration is compared to the intensity-ratio calibration in order to emphasize the effectiveness of the technique. Finally, results are evaluated for accuracy and a detailed uncertainty analysis is performed to fully assess the POD calibration. |
