Polymer/ceramic pressure-sensitive paints with reduced surface roughness were developed for measuring unsteady pressure fields in transonic flow. Four types of polymer/ceramic pressure-sensitive paints, each having different properties (such as particle size, mass content, and solvent), were formulated and applied to transonic windtunnel testsofa supercritical airfoil. The effectsofsurface roughnessonthe unsteady transonic flowonthe airfoil were evaluated at Mach 0.74 at a Reynolds number of 5.0 × 106. It was found that all four polymer/ceramic pressure-sensitive paints couldbe used to measure time-series pressure distributions, but the location of the shock wave and the root-mean-square pressure fluctuations differed, depending on the type of polymer/ceramic pressure-sensitive paint. Among the tested polymer/ceramic pressure-sensitive paints, havingan arithmetic surface roughnessof0.5 μmand a cutoff frequency of 3 kHz yielded practically the same data as a clean airfoil. Using this polymer/ceramic pressure-sensitive paint, propagation of pressure waves and oscillation of shock waves on the airfoil were clearly captured. A spectral analysis revealed that the fundamental frequency of shock-wave oscillation agreed very well with that calculated based on the mechanism proposed in previous studies. These results showed that the selected polymer/ceramic pressure-sensitive paint is an effective means by which to study transonic buffeting on airfoils and three-dimensional wings.
ASJC Scopus subject areas
- Aerospace Engineering