Paper doi abstract bibtex

A two-dimensional Shack-Hartmann wave-front sensor is used to study aero-optic distortion in turbulent boundary layers at transonic and hypersonic speeds, with and without gas injection. The large-scale motions in the outer layer, of the order of the boundary-layer thickness in size, are shown to dominate the aero-optic distortion. Gas injection always reduced the Strehl ratio, with helium injection generally giving lower Strehl ratios than nitrogen injection. The large aperture approximation is shown to be accurate for a wide variety of aberrations regardless of Mach number and gas injection. A new scaling argument for the root-mean-square phase distortion is proposed that appears to collapse the data better than previous models. Nomenclature C B = constant defined by Eq. (20), OPD rms K GD e M 2 e u 0 rms =U e rms C f = skin friction coefficient C w = constant defined by Eq. (16), OPD rms r 3=2 2 K GD e M 2 e C f p I = intensity K GD = Galdstone-Dale constant M = Mach number n = index of refraction p = pressure Re = Reynolds number based on freestream values and r = recovery factor r 1 = U i =U e r 2 = T i =T e r 3 = constant defined by Eq. (14), u 02 w q 0:5 = u 02 w q i T = temperature t = time U = velocity in the streamwise direction x = streamwise distance y = wall-normal distance from the flat plate model z = spanwise distance = ratio of specific heats = 99% boundary-layer thickness = displacement thickness = momentum thickness = integral length scale = wavelength of light = kinematic viscosity = density SL = sea level density in a standard atmosphere = shear stress Subscripts e = freestream value i = intermediate value rms = root mean square value w = value at the wall 0 = maximum value Superscripts = mean value 0 = fluctuation from the mean

@article{wyckham2009a, title = {Aero-{Optic} {Distortion} in {Transonic} and {Hypersonic} {Turbulent} {Boundary} {Layers}}, volume = {47}, url = {http://arc.aiaa.org}, doi = {10.2514/1.41453}, abstract = {A two-dimensional Shack-Hartmann wave-front sensor is used to study aero-optic distortion in turbulent boundary layers at transonic and hypersonic speeds, with and without gas injection. The large-scale motions in the outer layer, of the order of the boundary-layer thickness in size, are shown to dominate the aero-optic distortion. Gas injection always reduced the Strehl ratio, with helium injection generally giving lower Strehl ratios than nitrogen injection. The large aperture approximation is shown to be accurate for a wide variety of aberrations regardless of Mach number and gas injection. A new scaling argument for the root-mean-square phase distortion is proposed that appears to collapse the data better than previous models. Nomenclature C B = constant defined by Eq. (20), OPD rms K GD e M 2 e u 0 rms =U e rms C f = skin friction coefficient C w = constant defined by Eq. (16), OPD rms r 3=2 2 K GD e M 2 e C f p I = intensity K GD = Galdstone-Dale constant M = Mach number n = index of refraction p = pressure Re = Reynolds number based on freestream values and r = recovery factor r 1 = U i =U e r 2 = T i =T e r 3 = constant defined by Eq. (14), u 02 w q 0:5 = u 02 w q i T = temperature t = time U = velocity in the streamwise direction x = streamwise distance y = wall-normal distance from the flat plate model z = spanwise distance = ratio of specific heats = 99\% boundary-layer thickness = displacement thickness = momentum thickness = integral length scale = wavelength of light = kinematic viscosity = density SL = sea level density in a standard atmosphere = shear stress Subscripts e = freestream value i = intermediate value rms = root mean square value w = value at the wall 0 = maximum value Superscripts = mean value 0 = fluctuation from the mean}, number = {9}, journal = {AIAA Journal}, author = {Wyckham, Christopher M and Smits, Alexander J}, year = {2009}, }

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