A novel laminated OLED–PSP system for measurement on moving surfaces

A novel pressure-sensitive paint (PSP) system has been developed which uses an embedded organic light-emitting diode (OLED) layer as excitation, and thus eliminates the usual requirement of an external light source. This system consists of an OLED layer, an optical filter layer and a polymer-ceramic (PC) PSP layer with fast response. The OLED provides green excitation light (around 500 nm) for PSP, while the optical filter and (550 nm short-pass) removes unwanted longer wavelength light to prevent possible interference with the PSP signal. A PC-PSP layer is applied on top of the filter with well-controlled basecoat thickness (~ 10 μm) to allow sufficient light transmittance. It is also important that the OLED is modulated with a limited duty cycle and synchronized with the camera exposure to minimize uncertainties mostly due to the inherent heating effect of OLED. This OLED-based PSP has a pressure sensitivity comparable to the regular PC-PSP, and it is well-suited for pressure measurements on moving surfaces since its illumination field is independent of the model motion. Its advantage over a conventional PSP system was demonstrated through applications on a flapping plate under the impingement of a nitrogen jet.