Joint ONERA-DLR PSP measurements for unsteady characterization and future activities

Kurzfassung

Application of the PSP technique to unsteady aerodynamic flows requires specific measurement instrumentation. First of all, a dedicated paint as pressure sensor has to be designed in order to reduce the response time of the paint. Then, the instrumentation has to be able to acquire with high framing rate low light level intensities. Concerning the paint formulation, DLR has developed a high porosity paint where the luminescent dye is incorporated in a porous polymer. ONERA is working on a surface contact paint (anodized-aluminium PSP) where the dye is adsorbed on porous anodized-aluminium. The dynamic calibration of the unsteady paint (uPSP) consists in measuring the response of the paint under pressure variations. The calibration rig can generate either a pressure step, like in a shock tube or by opening a quick valve, or a periodic pressure variation. In this case, the frequency is limited to a maximum of 1 kHz. Above this value, the amplitude of pressure variations is too low. On the other hand, the shock tube can generate high pressure variations. Common measurements have been performed at ONERA with the DLR paint under sinusoidal pressure variations between 50 and 100Hz with amplitude of several thousands of Pascals. The aim of the test was to define a common procedure for unsteady PSP calibration. The response time of the high porosity paint is almost 10 ms, while the anodized-aluminium PSP has a response time of several tens of microseconds. The advantage of the DLR paint is that it can be spayed on any surface while the ONERA coating can be applied only on aluminium. Point-wise measurement systems coupled with a PMT is commonly used for calibration because they have high acquisition rate. Now, CMOS cameras allow high frame rate acquisition associated to high sensitivity. This type of camera has been recently purchased at ONERA. Wind tunnel tests are planned at DLR on a forced oscillating wing in 2006. Then, buffeting measurements should be performed in 2007. ONERA will repeat measurements, previously made in 2003, on a forced oscillating shock with the high speed camera instead of point-wise system.