Flow Disturbance and Surface Roughness Effects on Cross-Flow Boundary-Layer Transition in Supersonic Flows

Owens, Lewis R.; Beeler, George B.; Balakumar, Ponnampalam; McGuire, Patrick

doi:10.2514/6.2014-2638

Cited by 8 publications

(6 citation statements)

References 15 publications

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“…Ideally, transition research is conducted in low-disturbance wind tunnels with turbulence intensities of about 0.05%, but model size and Mach constraints contributed to our decision to use a conventional supersonic facility, the LaRC 20-Inch Supersonic Wind Tunnel (SWT). During previous swept-wing research in SWT [21], we measured freestream mass-flux turbulence levels of about 0.1%. These fluctuation levels are considered low enough to enable investigation of crossflow transition mechanisms in this tunnel, but these levels are expected to be higher than those in flight.…”

Section: A Swept-wing Modelmentioning

confidence: 99%

“…These profiles were input into a boundary-layer stability analysis using a Linear Stability Theory (LST) approach to predict the disturbance growth for the most-amplified stationary crossflow (SCF) wavelength. We chose a disturbance amplification factor (N=5.5 for a most-amplified SCF wavelength of 3 mm at M=2 and a unit Re =11.6 million/m design condition) to predict the expected laminar flow extent based upon our earlier 35° swept-wing experimental transition results in SWT [21].…”

Section: A Swept-wing Modelmentioning

confidence: 99%

“…Due to the overview perspective of this paper, we omit detailed descriptions of both the tunnel and flight test techniques. We refer readers to a detailed description of SWT in our earlier transition research [21] on a 35° sweptwing model. Similarly, more detailed information about the flight test technique can be found in previous boundarylayer transition flight research that also used the F-15B aircraft with the CLIP mounting system [23][24][25].…”

Section: B Supersonic Wind Tunnel Flight Vehicle and Supporting Computationsmentioning

confidence: 99%

“…Our swept-wing laminar flow research began with a preliminary study to develop an approach to assess boundarylayer transition due to crossflow transition mechanisms in the NASA Langley Research Center (LaRC) 20-Inch Supersonic Wind Tunnel (SWT) [21,22]. After establishing a viable assessment approach, we turned our attention to the task of designing a more sophisticated, highly-swept wing model capable of being tested in SWT and on the NASA Armstrong Flight Research Center (AFRC) F-15B Centerline Instrumented Pylon (CLIP) test fixture [23][24][25].…”

Section: Introductionmentioning

confidence: 99%

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Supersonic Crossflow Transition Control in Ground and Flight Tests

Owens

Beeler

King

et al. 2019

AIAA Scitech 2019 Forum

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This paper describes the use of distributed-roughness-element (DRE) patterns along a Mach 2 design swept-wing leading edge to increase the laminar flow extent and thereby reduce drag. One swept-wing model was tested in a supersonic wind tunnel as well as beneath a supersonic flight vehicle. Wing model surface data acquired during these tests included pressures, temperatures, and boundary-layer transition locations. Similarities and differences in experimental results are discussed. While wind tunnel and flight results show some differences, the wind tunnel results still provide key insights necessary for understanding how to design effective DRE patterns for use in flight applications. Experimental results demonstrate a DRE flow control effect observed in flight similar to that observed in the wind tunnel. Finally, a different perspective is discussed concerning what flow control role the DRE patterns might perform in any future swept-wing laminar flow control applications.

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Section: A Swept-wing Modelmentioning

confidence: 99%

Section: A Swept-wing Modelmentioning

confidence: 99%

Section: B Supersonic Wind Tunnel Flight Vehicle and Supporting Computationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Supersonic Crossflow Transition Control in Ground and Flight Tests

Owens

Beeler

King

et al. 2019

AIAA Scitech 2019 Forum

Self Cite

View full text Add to dashboard Cite

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“…Arrays of discrete roughness elements were used on swept wings to excite a stable wavelength of crossflow vortices. [5][6][7] Studies of arrays of isolated roughness elements can provide insight into the interaction of these elements.…”

Section: Introductionmentioning

confidence: 99%

Transition Induced by Tandem Rectangular Roughness Elements on a Supersonic Flat Plate

Chou

King

Kegerise

2018

2018 Fluid Dynamics Conference

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The flow behind two rectangular roughness elements with a height approximately 38-41% of the boundary layer thickness was examined with a hot-wire probe. The rectangular roughness elements are oriented so that one element was at a +45-degree angle relative to the leading edge of the plate. A second roughness element was placed 7.16 mm downstream of the first one with either the same orientation relative to the leading edge of the plate, or an opposing orientation of −45 degrees from the leading edge. Mean mass-flux and total-temperature profiles of the flow field downstream of the tandem roughness elements were examined for mean-flow distortion. Using streak strength as a measure of mean-flow distortion, the tandem roughness elements had approximately the same amount of distortion, regardless of their relative orientation. Mass-flux fluctuation profiles show that the dominant mode downstream of the tandem roughness elements with the same orientation was similar to that of a single roughness element and centered at a frequency of approximately 55 kHz. The dominant instability downstream of the tandem roughness elements with opposing orientation was centered at a frequency of 65 kHz and grew more slowly than the instabilities behind the single roughness element.

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The secondary instabilities of stationary cross-flow vortices in a Mach 6 swept wing flow

Chen

Liu

et al. 2019

J. Fluid Mech.

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The secondary instabilities of stationary cross-flow vortices in a Mach 6 swept wing flow are studied using Floquet theory. High-frequency secondary instability modes of ‘y’ mode on top of stationary cross-flow vortices, and ‘z’ mode concentrating on the shoulder of the stationary cross-flow vortex are found. The most unstable secondary instability mode is always the ‘z’ mode as in incompressible swept wing flows. A new secondary instability mode concentrating on the trough of the stationary cross-flow vortex is found. The balance analysis of disturbance kinetic energy shows that the new mode belongs to the class of ‘y’ mode. The growth rate of the new ‘y’ mode located on the trough of the stationary cross-flow vortex is significantly larger than that of the ‘y’ mode on top of the stationary cross-flow vortex, and is comparable with the growth rate of the ‘z’ mode. It is also found that the new ‘y’ mode with higher frequency can evolve into the ‘z’ mode further downstream. The role of the pressure fluctuation term, including the pressure diffusion and pressure dilatation, in the energy production of secondary instability modes, is also investigated. It is shown that the pressure diffusion will only enhance the growth rate of the ‘z’ mode with higher frequency, but has little influence on other types of secondary instability mode. However, the pressure dilatation term arising from non-vanishing velocity divergence will reduce the growth rates of all secondary instability modes.

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Flow Disturbance and Surface Roughness Effects on Cross-Flow Boundary-Layer Transition in Supersonic Flows

Cited by 8 publications

References 15 publications

Supersonic Crossflow Transition Control in Ground and Flight Tests

Supersonic Crossflow Transition Control in Ground and Flight Tests

Transition Induced by Tandem Rectangular Roughness Elements on a Supersonic Flat Plate

The secondary instabilities of stationary cross-flow vortices in a Mach 6 swept wing flow

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