Unsteady PSP Measurement of Transonic Buffet on a Wing

Abstract

In this study, unsteady pressure field caused by transonic buffeting phenomena on a generic transport model was analyzed using unsteady PSP. The tests were conducted in the JAXA 2-m Transonic Wind Tunnel at M=0.85 and the model angle of attack was varied between 2.5 and 6.8 degrees. From the obtained unsteady PSP data, the RMS of pressure fluctuation was calculated to detect the areas with strong shock oscillation. Spectral analysis was also conducted in order to find frequencies of shock oscillation and their correlation with pressure fluctuation. As the angle of attack increases, the shock position moves upstream and shock oscillation becomes stronger. At 6.8 degrees, two distinct areas with strong shock oscillation were observed. The spectral analysis shows that, under buffeting conditions, shock oscillation frequencies are distributed around either of 490 Hz or 365 Hz. Noticeable effects from the PSP coating on the measured aerodynamic forces were noticed, indicating that even the small roughness of the unsteady PSP coating has an influence on the transonic buffeting phenomena. Nomenclaturet = time p = pressure M ∞ = Mach number Re = Reynolds number c = chord length c = mean aerodynamic chord length x = model stream wise location  = angle of attack I = PSP emission intensity p RMS = Root-Mean-Square of pressure fluctuation p = difference from time-averaged pressure  = wing spanwise location (non-dimensional) X(f) = Fast Fourier Transform results of  ave /I N FFT = the number of data points for FFT (=2048) f S = frame rate of the high-speed camera Coh 2 = coherence 1 Master's course student, 2 S XX , S YY = auto-spectrum of X and Y S XY = cross-spectrum between X and Y PSD = Power spectrum density Subscripts: ref = refrence condition, 100kPa ave = time-averaged

Analysis and Comparison of Transonic Buffet Phenomenon over Several Three-Dimensional Wings

“…10c, Fig. 12, Sartor and Timme [32], and Sugioka et al [17]), while the tendency with the Mach number is less clear and needs further study. Furthermore, a convective behavior is found at the buffet Strouhal number on the wing for all models.…”

“…This phenomenon is known as buffet offset [8,15,16]. Sugioka et al [17], Lawson et al [18], and Koike et al [19] performed experimental tests at high M − α, but the same effect was not observed for the 3D buffet.…”

“…Eckstrom et al [21,22] presented a complete study of mean pressure coefficients and unsteady pressure signals for different Mach numbers but without the analysis of the spectral content. More recently, unsteady pressure-sensitive paint (PSP) has been successfully used by Steimle et al [23], Merienne et al [24], Sugioka et al [17], and Lawson et al [18] to analyze the unsteady flowfield for transonic buffet over a transport-type swept wing Two campaigns, analyzed in the present Paper, have already been presented in previous studies. Molton et al [13] showed the spectral analysis and results of buffet control by VGs for the ONERA research project BUFET'N Co. Dandois [14] performed a complete analysis of BUFET'N Co and AVERT databases.…”

Unsteady Pressure Measurement of Transonic Buffet on NASA Common Research Model

“…These researches also revealed that the large difference of the peak frequencies [8][9][10] . Furthermore, we clarify the difference of the effect of the vortex generators (VGs) on the unswept and the swept wing.…”

“…These techniques are being developed by many organizations and researchers in order to analyze the unsteady issues in aerospace engineering 3,9,10,[13][14][15][16] . Unsteady experimental data are essentially important to validate these methods.…”