Multi-resolution analysis of aero-optical effects in a supersonic turbulent boundary layer

Studying the aero-optical effects induced by turbulent structures with different scales helps determine the capture scale of turbulent structures in experiments/calculations and improve the turbulence breakup device. In this paper, the density field of a supersonic turbulent boundary layer at Ma=3.0 was measured based on the nano-tracer plane laser scattering technique. Two-dimensional orthogonal wavelet multi-resolution analysis was applied to obtain information about different flow scales. The ray-tracing method simulates the propagation of a Gaussian plane beam through the nonuniform flow field at different resolutions. The results show that the turbulent boundary layer thickness and its calculation method lead to the difference in scaling calculation results among the existing experiments. The turbulent structures about 0.7δ contribute most to aero-optical effects. With the reduction of the resolution, the contribution of small turbulent structures to aero-optical effects reduces obviously. When the minimum scale of turbulent structures captured is larger than 0.072δ, the resolution can no longer reflect the real aero-optics results of turbulent structures. The smallest optically active scale predicted is 0.017δ in Mani's theory. The turbulent structures smaller than 0.018δ have little effect on optical path difference (OPD), and the higher-order quantities change significantly around 0.009δ∼0.018δ. According to experimental results, it is promising to improve the aero-optical suppression effects by breaking the large eddy into the turbulent structures smaller than 0.018δ, or even 0.009δ.