Global analysis of nonlinear second-mode development in a Mach-6 boundary layer from high-speed schlieren data.
| Title: | Global analysis of nonlinear second-mode development in a Mach-6 boundary layer from high-speed schlieren data. |
|---|---|
| Authors: | Sousa, Cole E., Kennedy, Richard E., King, Rudolph A., Bathel, Brett F., Weisberger, Joshua M., Laurence, Stuart J. |
| Source: | Experiments in Fluids; Feb2024, Vol. 65 Issue 2, p1-22, 22p |
| Subject Terms: | BOUNDARY layer (Aerodynamics), NONLINEAR analysis, PROPER orthogonal decomposition, REYNOLDS number, SPECTRAL energy distribution, POWER spectra |
| Abstract: | The second-mode instability on a 7° half-angle sharp cone at Mach 6 is analyzed using high-speed calibrated schlieren imagery at a frame rate near the expected fundamental frequency. Experiments were conducted in the NASA Langley 20-Inch Mach 6 facility at unit Reynolds numbers between 6.56 × 10 6 and 9.71 × 10 6 m - 1 . Time-resolved pixel intensity signals throughout the boundary layer are reconstructed using spatially available data in the schlieren images to recover an effective sampling rate of over 10 MHz; these are then converted to quantitative density gradients using a thin-lens-based calibration technique. A global analysis is performed on the schlieren data to investigate the nonlinear growth of the second-mode fundamental and harmonic content. Pointwise measures of the autobicoherence are used to identify specific triadic interactions and the locations of their highest levels of quadratic phase coupling. Significant resonance interactions between the second-mode fundamental and harmonic instabilities were found along with interactions between these and the mean flow. Bispectral mode decomposition is employed to educe the flow structures associated with these interactions. A similar analysis is performed for the power spectrum, with power spectral densities computed for each pixel's time-series and spectral proper orthogonal decomposition employed to derive the modal structure and energy of the flow at specific frequencies. Comparisons between the bispectral quantities and second-mode power show that nonlinear interactions, particularly resonance interactions, are closely correlated with spatiotemporal modulation of disturbances during the nonlinear stage of transition. [ABSTRACT FROM AUTHOR] |
| Copyright of Experiments in Fluids is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.) | |
| Database: | Complementary Index |
Be the first to leave a comment!