Aero-Optical Effects of Supersonic Boundary Layers

Abstract

Aero-optical measurements of a zero-pressure-gradient, supersonic boundary layer along the test-section wall at M 2:0 were performed using a Malley probe. The Malley probe captured both the amplitude of optical distortions and the convective speed. The convective speed of the optically active structures inside the supersonic boundary layer was found to be 0.84 of the freestream speed. The deflection-angle spectra were found to collapse with the local displacement thickness. The streamwise correlation function for the supersonic boundary layer revealed the presence of a pseudoperiodic structure with the typical size of 1.5 of the local boundary-layer thickness. A new model was developed to describe aero-optical effects of both the subsonic and the supersonic boundary layers. Finally, this new model and several other theoretical scalings were tested in the attempt to collapse both subsonic and supersonic boundary-layer aero-optical results.

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

“…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). In addition, in figure 14 experimental result for a supersonic boundary layer at M = 2.0 from Gordeyev et al (2012) is presented as a solid star; this result also agrees well with the model equation (4.8). Wittich et al (2007) presented experimental measurements of the optical distortions in a subsonic, M < 0.5, boundary layer for adiabatic walls, using simple scaling arguments, which can be described as OPD rms = (1.7 ± 0.2) × 10 −5 (ρ ∞ /ρ SL )δ * M 2 , where δ * is the displacement thickness and ρ SL is the sea-level density (= 1.225 kg m −3 ).…”

“…Other density-correlation lengths available in the literature were tested by Gordeyev, Jumper & Hayden (2012) and Smith & Gordeyev (2013b) and showed very similar results for G(M). Here C f was estimated from the Reynolds number using von Kármán-Schoenherr correlation (Bardina, Huang & Coakley 1980) and applying a compressible correction (Eckett 1955).…”

Computation of the Aero-Optical Effect of a Helicopter Rotor Wake Using Unsteady RANS and LES

“…n recent years the optical environment encountered by high-energy laser (HEL) systems on fixed-wing platforms has received increased attention [1][2][3][4][5][6][7]. These platforms commonly employ hemisphere-on-cylinder turrets because of their large field of view, ability to easily aim the outgoing beam, and similar aerodynamic characteristics in all orientations.…”

Investigation of turbulent shock boundary interaction unsteadiness and its effects on aero-optics in a Mach 2 ramp flow

“…Reviews of this interaction between flow turbulence and optics can be found in references by Sutton, 26 Jumper and Fitzgerald 27 and Wang et al 28 In the specific area of aero-optics at speeds greater than Mach 1, Stine and Winovich 29 looked at Mach numbers up to 2.5 back in the 1950s and was later re-analyzed by Sutton 30 in the 1980s. More recently, Gordeyev et al 31 considered aero-optics in a supersonic boundary layer at Ma=2 with a Malley probe. Gao et al 32 experimentally considered the statistical characteristics of the beam tilts in a Mach 3 boundary layer.…”

“…Two recent hypersonic flow studies have conducted: Yanta et al 33 at Ma=7 and Wyckham & Smits at Ma=7.8. 34 In terms of interaction of aeroptics with shock waves, the study by Gordeyev et al 31 placed a wedge in the windtunnel and measured through a weak mach wave. A more recent work by Gordeyev et al 35 looked at passive flow control devices to eliminate shock formation on a turret in transonic flow.…”