Scaling of square-prism shear layers
Autor: | D. C. Lander, Michael Amitay, Daniel Moore, Chris Letchford |
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Rok vydání: | 2018 |
Předmět: |
Length scale
Materials science Mechanical Engineering Reynolds number Mechanics Condensed Matter Physics Boundary layer thickness 01 natural sciences Instability 010305 fluids & plasmas 010309 optics symbols.namesake Shear layer Shear (geology) Transition point Mechanics of Materials 0103 physical sciences symbols Scaling |
Zdroj: | Journal of Fluid Mechanics. 849:1096-1119 |
ISSN: | 1469-7645 0022-1120 |
Popis: | Scaling characteristics, essential to the mechanisms of transition in square-prism shear layers, were explored experimentally. In particular, the evolution of the dominant instability modes as a function of Reynolds number were reported in the range $1.5\times 10^{4}\lesssim Re_{D}\lesssim 7.5\times 10^{4}$. It was found that the ratio between the shear layer frequency and the shedding frequency obeys a power-law scaling relation. Adherence to the power-law relationship, which was derived from hot-wire measurements, has been supported by two additional and independent scaling considerations, namely, by particle image velocimetry measurements to observe the evolution of length and velocity scales in the shear layer during transition, and by comparison to direct numerical simulations to illuminate the properties of the front-face boundary layer. The nonlinear dependence of the shear layer instability frequency is sustained by the influence of $Re_{D}$ on the thickness of the laminar front-face boundary layer. In corroboration with the original scaling argument for the circular cylinder, the length scale of the shear layer was the only source of nonlinearity in the frequency ratio scaling, within the range of Reynolds numbers reported. The frequency ratio scaling may therefore be understood by the influence of $Re_{D}$ on the appropriate length scale of the shear layer. This length scale was observed to be the momentum thickness evaluated at a transition point, defined where the Kelvin–Helmholtz instability saturates. |
Databáze: | OpenAIRE |
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