Application of pressure-sensitive paint to low-speed flow around a U-bend of strong curvature

Abstract

Two in-house Pressure-Sensitive Paint (PSP) formulations have been developed and tested in the low-speed regime on the flow around a U-bend of strong curvature. The two PSP formulations use trisBathophenanthroline Ruthenium Perchlorate (Ru (II)) and Platinum tretakis (pentafluorophenyl) Porphyrin (PtTFPP) as their photoactive molecules, incorporated in identical sol-gel matrices. Ru (II) emits a broad peak centered at 610nm while PtTFPP emits a much narrower peak at 650nm. The paints were illuminated using two in-house constructed blue LED lights with peak emission of 468nm. These luminophores have been tested with gauge inlet pressures of 3000 and 1250 Pa respectively. A further sample was tested with a gauge pressure of 500 Pa. In-situ calibration was utilized to minimize the temperature dependency change between wind-on and wind-off images. Both paints captured the flow characteristics and gave predictable surface pressure maps despite the challenges inherent with using such low pressures. Keywords: PSP, low-speed, U-bend, internal flow INTRODUCTIONSeveral researchers have attempted to use pressuresensitive paints (PSP) at low speeds despite the inherent difficulties with such applications [1,2,3,4,5,6,7]. Of these researchers Bell [3] and Le Sant [7] managed extremely low errors (± 50 Pa). However, all of the applications of PSP to low-speed flow have been performed in large-scale wind tunnels. To this end it was decided to test the PSP formulations in use at the University of Manchester on a low-speed, internal flow.

Static and Wind-on Performance of Polymer-Based Pressure-Sensitive Paints Using Platinum and Ruthenium as the Luminophore

“…This is evidenced by the absence of the flow features, like the spanwise vortex pair and the separation line in the surface pressure map shown in Figure 10b. Similar conclusions were also drawn by Zare-Behtash et al [38] and Quinn et al [26,34]. In fact, an interesting phenomenon can be observed by plotting the surface pressure profile, measured by the two PSPs being studied, along the centreline of the contour bump, as shown in Figure 11.…”

“…One of the major drawbacks in pressure measurements using pressure-sensitive paints is their temperature dependency [6,18,26]. Therefore, it is necessary to investigate the temperature sensitivity characteristics of the two polymer-based PSPs being studied.…”

“…, 5 s) followed by capturing another forty “wind-off” images immediately after the wind tunnel operation. Wind-off images were captured after each wind tunnel test in order to account for the temperature effects caused by shock and expansion waves to the contour bump model [26,34]. Captured images were stored in a Windows-based computer and post-processed by an in-house-developed MATLAB program.…”

“…Platinum tetrakis (pentafluorophenyl) porphyrin (PtTFPP) and tris-bathophenanthroline ruthenium II (Ru (II)) were used as the luminophores. The peak absorption spectra of the PtTFPP and Ru (II) molecules are 395 and 457 nm, respectively [26]. The peak emission spectrum of the PtTFPP molecules is 650 nm when illuminated by an ultra-violet light source with an emission wavelength of 395 nm.…”

Transverse jet-cavity interactions with the influence of an impinging shock

“…[32][33][34][35][36][37] The in-house developed PSP technology used in the present study has been successfully applied in a variety of flow conditions and has been found in all cases to provide accurate pressure measurements when compared to conventional pressure transducers. [38][39][40][41][42][43][44] The PSP setup consists of a LaVision Image Intense 12-bit CCD camera with a 590nm long-pass filter mounted on the lens, and UV LEDs with peak wavelength of 390nm were used for image acquisition. Ruthenium is used as the luminohpore molecules in the current recipe.…”