Turbulent spots induced by pairs of roughness elements in a blunt-body hypersonic boundary layer

2017 ◽  
Author(s):  
Oliver W. Taylor ◽  
Paul J. Bruce
Keyword(s):  
Boundary Layer ◽  
Blunt Body ◽  
Hypersonic Boundary Layer ◽  
Turbulent Spots ◽  
Roughness Elements

Infrared thermography of hypersonic boundary layer transition induced by isolated roughness elements

2021 ◽  
Author(s):  
Shicheng Liu ◽  
Meng Wang ◽  
Hao Dong ◽  
Tianyu Xia ◽  
Lin Chen ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Infrared Thermography ◽  
Roughness Element ◽  
Transition Process ◽  
Boundary Layer Transition ◽  
Hypersonic Boundary Layer ◽  
Layer Transition ◽  
Leading Role ◽  
Roughness Elements ◽  
Element Shape

Roughness element induced hypersonic boundary layer transition on a flat plate is investigated using infrared thermography at Ma = 5 and 6 flow condition. Surface Stanton number is acquired to analyze the effect of roughness element shape and height on the transition process. The correlation between the vortex structure induced by roughness element and the wall heat streaks is established. The results indicate that higher roughness element would induce stronger streamwise heat flux streaks, lead to transition advance in streamwise centerline and increase the width of spanwise wake. Moreover, for low roughness element, the effect of the shape is not obvious, and the height plays a leading role in the transition; for tall roughness element, the effect on accelerating transition for the diamond roughness element is the best, the square is the worst, and the shape plays a leading role in the transition.

scholarly journals Pressure fluctuations beneath instability wavepackets and turbulent spots in a hypersonic boundary layer

2014 ◽  
Vol 756 ◽  
pp. 1058-1091 ◽  
Author(s):  
Katya M. Casper ◽  
Steven J. Beresh ◽  
Steven P. Schneider
Keyword(s):  
Boundary Layer ◽  
Pressure Fluctuation ◽  
Electrical Breakdown ◽  
Pressure Fluctuations ◽  
Spanwise Direction ◽  
Hypersonic Boundary Layer ◽  
Nozzle Wall ◽  
Turbulent Spots ◽  
Fluctuation Field ◽  
Second Mode

AbstractTo investigate the pressure-fluctuation field beneath turbulent spots in a hypersonic boundary layer, a study was conducted on the nozzle wall of the Boeing/AFOSR Mach-6 Quiet Tunnel. Controlled disturbances were created by pulsed-glow perturbations based on the electrical breakdown of air. Under quiet-flow conditions, the nozzle-wall boundary layer remains laminar and grows very thick over the long nozzle length. This allows the development of large disturbances that can be well-resolved with high-frequency pressure transducers. A disturbance first grows into a second-mode instability wavepacket that is concentrated near its own centreline. Weaker disturbances are seen spreading from the centre. The waves grow and become nonlinear before breaking down to turbulence. The breakdown begins in the core of the packets where the wave amplitudes are largest. Second-mode waves are still evident in front of and behind the breakdown point and can be seen propagating in the spanwise direction. The turbulent core grows downstream, resulting in a spot with a classical arrowhead shape. Behind the spot, a low-pressure calmed region develops. However, the spot is not merely a localized patch of turbulence; instability waves remain an integral part. Limited measurements of naturally occurring disturbances show many similar characteristics. From the controlled disturbance measurements, the convection velocity, spanwise spreading angle, and typical pressure-fluctuation field were obtained.

Numerical study of hypersonic boundary layer transition on a blunt body

1997 ◽  
Author(s):  
Heath Johnson ◽  
Graham Candler ◽  
Mary Hudson ◽  
Heath Johnson ◽  
Graham Candler ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Blunt Body ◽  
Numerical Study ◽  
Boundary Layer Transition ◽  
Hypersonic Boundary Layer ◽  
Layer Transition
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