Aero-optical study of a NC-135 fuselage boundary layer

Experimental studies of aero-optical properties of subsonic turbulent boundary layers

“…The pioneering use of this new wavefront-sensing device in making optical measurements in turbulent subsonic boundary layers (Gordeyev et al 2003) has shown that it yields the most accurate and highly time-resolved information about optical distortions for turbulent boundary layers with bandwidths > 100 kHz. Analysis of Malley-probe optical data (Gordeyev et al 2003;Wittich, Gordeyev & Jumper 2007) has shown that optical distortions are proportional to the boundary-layer thickness, the free-stream density and the square of the free-stream Mach number, OPD rms ∼ δρM 2 , which is consistent with the finding by Rose (1979), but not by Gilbert (1982) or Masson et al (1994). It was also shown that optical distortions convect at a constant speed of 0.82-0.85 of the free-stream speed, which suggests that optically active structures reside in the outer portion of the boundary layer.…”

“…The data agree quite well at high values of ρ ∞ δM 2 C f G(M), but at low values of ρ ∞ δM 2 C f G(M), Gilbert's data are consistently higher than (4.8) predicts. Masson et al (1994) revisited some of the Gilbert's data and found a systematic error in reducing that data, which lead to overestimating optical distortions at low Mach numbers. After a correction, new data, also plotted in figure 14 both from direct (optical) and indirect (hotwire-based) measurements, agree much better with (4.8).…”

“…These interferometric methods provided a time-averaged assessment of the optical phase variance over the aperture; however, these methods provided no information concerning either temporal frequencies or wavefront spectra. Masson, Wissler & McMackin (1994) revisited the Gilbert (1982) and Rose (1979) data and concluded that after removing systematic errors from Gilbert's data, OPD rms ∼ (ρM 2 ) 1.16 . Also Masson et al (1994) found that there appeared to be a systematic difference between direct and indirect wavefront error measurements, with the interferometric estimates consistently yielding higher estimates of the OPD rms than the hotwire estimates, but could not offer a reasonable explanation as to why optical and hotwire data did not agree in magnitude.…”

“…Masson, Wissler & McMackin (1994) revisited the Gilbert (1982) and Rose (1979) data and concluded that after removing systematic errors from Gilbert's data, OPD rms ∼ (ρM 2 ) 1.16 . Also Masson et al (1994) found that there appeared to be a systematic difference between direct and indirect wavefront error measurements, with the interferometric estimates consistently yielding higher estimates of the OPD rms than the hotwire estimates, but could not offer a reasonable explanation as to why optical and hotwire data did not agree in magnitude. Overall, Sutton (1985) surmised that aero-optics was a mature discipline requiring only the measurement of the turbulence statistics of a few additional flows (Jumper & Fitzgerald 2001).…”

Aero-Optical Measurements in a Heated, Subsonic, Turbulent Boundary Layer

“…However, he concluded that the square of the OPD rms is linearly dependent on the dynamic pressure, € OPD rms 2~q . In 1994 Masson et al 8 revisited the Gilbert and…”