Liang L.   ren x.   yin x.  

Research on Pressure Sensitive Paints Experimental Technology in Low Speed Wind Tunnel

Reporter: Liang L.

        Surface pressure measurement can provide much key information of flow phenomena, such as load distribution, shock wave, flow separation and boundary layer transition etc.. Taking the pressure test of OA312 airfoil model pressure sensitive paint as an example, we tend to study the application of pressure sensitive paint in low- speed wind tunnel.
        Tests are performed in the 1.4m×1.4m low-speed wind tunnel, which is a straight-flow closed test section, 26.75m long. In detail, its center elevation line is 3.9m high, the test size is 1.4m × 1.4m × 2.8m and the maximum wind speed is 65m/s. The test model is OA312 airfoil with the chord length of 300mm and the span length of 700mm, as shown in Fig.1. To be exact, their ratio is 2.3:1. At the centre of the model is the pressure profile, on which nine measuring points are adopted. The coated pressure sensitive paint area is 280mm × 280mm, covering scanning pressure points. This test uses DSA3217 portable electronic scanning system to measure the surface pressure of 9 measuring points on the airfoil model and thus the results can be compared with those of the pressure sensitive paint measurement. In addition, BinaryFIB pressure sensitive paint and LM2X-DM light source produced by ISSI company are adopted in this test. Meanwhile PCO.edge.SCMOS camera is used to get data based on scientific CMOS image sensor.
        This test is done at steady velocity and the selected three wind speeds are respectively 30m/s, 40m/s and 50m/s. Six angles on the model are selected. They are 0°, 5°, 10°, 15°, 20°, 25°. On the other hand, the local atmospheric pressure is considered as the pressure datum and the tem-perature in the tunnel as the surface temperature of the model.
        The results show that this test has good repeatability, as shown in Fig.2-4, but there exists a bigger system error. The pressure distribution measurement result of pressure sensitive paint is basi-cally consistent with that of scanning result, with random uncertainty for about 160Pa. In view of the large curvature feature of the airfoil leading edge, the surface light intensity is not even and there is a bigger error in measurement results between the two methods. But the error is smaller in the middle part.

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