Characterization of Periodic Unsteadiness Generator for Secondary Flow Studies

Fletcher, Nathan; Marks, Christopher R.; Sondergaard, Rolf; Wolff, Mitch

doi:10.2514/6.2019-0622

Cited by 5 publications

(1 citation statement)

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“…Although bar wake generators provide an accurate representation for the 2-D wake component, they cannot accurately represent the endwall flow structures of front-loaded high-lift airfoils. Recently developed new devices for investigating unsteady wake effects in linear cascades, such as the periodic unsteadiness device proposed by Fletcher et al [25,26], cut down even more on the mechanical complexity and allow for a precise adjustment of the wake velocity deficit and frequency.…”

Section: Introductionmentioning

confidence: 99%

Large-Eddy Simulation of Low-Pressure Turbine Cascade with Unsteady Wakes

Robison

Groß

2021

Aerospace

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To better understand the wake effects at low Reynolds numbers, large-eddy simulations of a 50% reaction low-pressure turbine stage and a linear cascade with two different bar wake generators were carried out for a chord Reynolds number of 50,000. For the chosen front-loaded high-lift airfoil, the endwall structures are stronger than for more traditional mid-loaded moderate-lift airfoils. By comparing the 50% reaction stage results with the bar wake generator results, insight is gained into the effect of the three-dimensional wake components on the downstream flow field.For the cases with bar wake generator, the endwall boundary layer is growing faster because of the relative motion of the endwall with respect to the freestream. The half-width of the wake is approximately matched for the larger one of the two considered bar wake generators. To improve the quality of the phase-averaged flow fields, the proper orthogonal decomposition was employed as a filter to remove the low-energy unsteady flow field content. Both the mean flow and filtered phase-averaged flow fields were analyzed in detail. Visualizations of the phase-averaged flow field reveal a periodic suppression of the laminar suction side separation from the downstream airfoil even for the smaller bar wake generator. The passage vortex is entirely suppressed for the 50% reaction stage and for the larger bar wake generator. Furthermore, the phase-averaged data for the 50% reaction stage reveal a new longitudinal flow structure that is traced back to near-wall wake vorticity. This flow structure is missing for the bar wake generator cases.

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Section: Introductionmentioning

confidence: 99%