Journal ArticleDOI
Multiresolution analysis of density fluctuation in supersonic mixing layer
TLDR
In this paper, the multiresolution analysis of supersonic mixing layer based on experimental images is still a formidable challenge, due to the difficulties in measuring su-personic density field.Abstract:
Due to the difficulties in measuring supersonic density field, the multiresolution analysis of supersonic mixing layer based on experimental images is still a formidable challenge. By utilizing the recently developed nanoparticle based planar laser scattering method, the density field of a supersonic mixing layer was measured at high spatiotemporal resolution. According to the dynamic behavior of coherent structures, the multiresolution characteristics of density fluctuation signals and density field images were studied based on Taylor’s hypothesis of space-time conversion and wavelet analysis. The wavelet coefficients reflect the characteristics of density fluctuation signals at different scales, and the detailed coefficients reflect the differences of approximation at adjacent levels. The density fluctuation signals of supersonic mixing layer differ from the periodic sine signal and exhibit similarity to the fractal Koch signal. The similarity at different scales reveals the fractal characteristic of mixing layer flowfield. The two-dimensional wavelet decomposition and reconstruction of density field images extract the approximate and detailed signals at different scales, which effectively resolve the characteristic structures of the flowfield at different scales.read more
Citations
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Visualization of coherent structures in a supersonic flat-plate boundary layer
TL;DR: In this article, a flat-plate zero-pressure-gradient boundary layer at Mach 3 was visualized via nanoparticle-based planar laser scattering (NPLS), and coherent structures such as an individual hairpin vortex and hairpin packet were identified in the streamwise-wall-normal plane on the basis of the now accepted hairpin model.
Journal ArticleDOI
Aero-optical aberration measuring method based on NPLS and its application
TL;DR: In this paper, the wavefront aberration induced by a cross-section of supersonic flow field could be measured by ray tracing, and the results of high spatiotemporal resolution reveal fine wavefront structures.
Journal ArticleDOI
Characteristics of mixing enhanced by streamwise vortices in supersonic flow
TL;DR: In this article, a planar laser scattering method and particle image velocimetry are employed to generate large scale streamwise vortices, Kelvin-Helmholz Vortices and the formation of vortex clusters.
Journal ArticleDOI
Optical path difference of the supersonic mixing layer
TL;DR: The results indicate that aero-optical aberrations can severely limit the performance of airborne laser systems.
Journal ArticleDOI
Flow visualization of the large-scale structures in supersonic mixing layer with a recirculation flow region
TL;DR: Graphical Abstracts: as mentioned in this paper, Section 3.1.2.3.1, Section 2.2, Section 4.3, Section 5.4, Section 6.
References
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Journal ArticleDOI
On density effects and large structure in turbulent mixing layers
Garry L. Brown,Anatol Roshko +1 more
TL;DR: In this article, Spark shadow pictures and measurements of density fluctuations suggest that turbulent mixing and entrainment is a process of entanglement on the scale of the large structures; some statistical properties of the latter are used to obtain an estimate of entrainedment rates, and large changes of the density ratio across the mixing layer were found to have a relatively small effect on the spreading angle.
Journal ArticleDOI
Multiresolution approximations and wavelet orthonormal bases of L^2(R)
TL;DR: In this paper, the authors study the properties of multiresolution approximation and prove that it is characterized by a 2π periodic function, which is further described in terms of wavelet orthonormal bases.
Journal ArticleDOI
The Spectrum of Turbulence
Journal ArticleDOI
The compressible turbulent shear layer: an experimental study
TL;DR: In this paper, the growth rate and turbulent structure of the compressible, plane shear layer are investigated experimentally in a novel facility, where it is possible to flow similar or dissimilar gases of different densities and to select different Mach numbers for each stream.
Book
Schlieren and shadowgraph techniques
TL;DR: A review of recent developments in shadowgraph and schlieren visualization can be found in this paper, where the authors present a detailed overview of the shadowgraph technique for flow visualization.