Numerical Simulations of Transient Growth in a Mach 15 Boundary Layer over a Blunt Leading Edge

2003 ◽  
Author(s):  
Haibo Dong ◽  
Xiaolin Zhong
Keyword(s):  
Boundary Layer ◽  
Numerical Simulations ◽  
Leading Edge ◽  
Transient Growth ◽  
Blunt Leading Edge

Numerical simulations of boundary-layer bypass transition due to high-amplitude free-stream turbulence

2008 ◽  
Vol 613 ◽  
pp. 135-169 ◽  
Author(s):  
VICTOR OVCHINNIKOV ◽  
MEELAN M. CHOUDHARI ◽  
UGO PIOMELLI
Keyword(s):  
Boundary Layer ◽  
Numerical Simulations ◽  
Free Stream ◽  
Leading Edge ◽  
High Amplitude ◽  
Length Scale ◽  
Normal Velocity ◽  
Bypass Transition ◽  
Turbulent Spots ◽  
Free Stream Turbulence

Direct numerical simulations (DNS) of bypass transition due to high-amplitude free-stream turbulence (FST) are carried out for a flat-plate boundary layer. The computational domain begins upstream of the plate leading edge and extends into the fully turbulent region. Thus, there is noad hoctreatment to account for the initial ingestion of FST into the laminar boundary layer. We study the effects of both the FST length scale and the disturbance behaviour near the plate leading edge on the details of bypass transition farther downstream. In one set of simulations, the FST parameters are chosen to match the ERCOFTAC benchmark case T3B. The inferred FST integral length scaleL11is significantly larger (RL=UL11/ν = 6580) than that employed in previous simulations of bypass transition (RL≃ 1000). An additional set of simulations was performed atRL= 1081 to compare the transition behaviour in the T3B case with that of a smaller value of FST length scale. The FST length scale is found to have a profound impact on the mechanism of transition. While streamwise streaks (Klebanoff modes) are observed at both values of the FST length scale, they appear to have clear dynamical significance only at the smaller value ofRL, where transition is concomitant with streak breakdown. For the T3B case, turbulent spots form upstream of the region where streaks could be detected. Spot precursors are traced to quasi-periodic spanwise structures, first observed as short wavepackets in the wall-normal velocity component inside the boundary layer. These structures are reoriented to become horseshoe vortices, which break down into young turbulent spots. Two of the four spots examined for this case had a downstream-pointing shape, similar to those found in experimental studies of transitional boundary layers. Additionally, our simulations indicate the importance of leading-edge receptivity for the onset of transition. Specifically, higher fluctuations of the vertical velocity at the leading edge of the plate result in higher levels of streamwise Reynolds stress inside the developing boundary layer, facilitating breakdown to turbulence.

Leading-edge effects in bypass transition

2007 ◽  
Vol 572 ◽  
pp. 471-504 ◽  
Author(s):  
S. NAGARAJAN ◽  
S. K. LELE ◽  
J. H. FERZIGER
Keyword(s):  
Boundary Layer ◽  
Leading Edge ◽  
Bypass Transition ◽  
Turbulent Spot ◽  
Eddy Simulation ◽  
Turbulence Transition ◽  
Large Eddy ◽  
Low Speed Streaks ◽  
Vortical Disturbance ◽  
Blunt Leading Edge

The effect of a blunt leading edge on bypass transition is studied by numerical simulation. A mixed direct and large-eddy simulation of a flat plate with a super-ellipse leading edge is carried out at various conditions. Onset and completion of transition is seen to move upstream with increasing bluntness. For sharper leading edges, at lower levels of turbulence, transition usually occurs through instabilities on low-speed streaks as observed by Jacobs & Durbin (2001) and Brandt et al. (2004) whereas increasing either the turbulence intensity or the leading-edge bluntness brings into play another mechanism. Free-stream vortices are amplified at the leading edge because of stretching. In the case of particularly strong vortices, this interaction induces a localized streamwise vortical disturbance in the boundary layer which then grows as it convects downstream and eventually breaks down to form a turbulent spot. These disturbances, which are localized and hence wavepacket-like, move at speeds in the range 0.55 U∞–0.65 U∞ and occur in the lower portion of the boundary layer. Simulations conducted with isolated vortices confirm such a response of the boundary layer.

scholarly journals Hypersonic boundary layer receptivity on flat plate with blunt leading edge due to acoustic disturbance

2021 ◽  
Vol 1786 (1) ◽  
pp. 012037
Author(s):  
Yifeng Zhang ◽  
Jianqiang Chen ◽  
Xianxu Yuan ◽  
Xi Chen ◽  
Xinghao Xiang
Keyword(s):  
Boundary Layer ◽  
Flat Plate ◽  
Leading Edge ◽  
Hypersonic Boundary Layer ◽  
Acoustic Disturbance ◽  
Blunt Leading Edge

INFLUENCE OF THE PLATE LEADING-EDGE SHAPE AND THICKNESS ON THE BOUNDARY LAYER LAMINAR-TURBULENT TRANSITION IN HYPERSONIC FLOW

2019 ◽  
Vol 50 (5) ◽  
pp. 461-481
Author(s):  
Sergei Vasilyevich Aleksandrov ◽  
Evgeniya Andreevna Aleksandrova ◽  
Volf Ya. Borovoy ◽  
Andrey Vyacheslavovich Gubernatenko ◽  
Vladimir Evguenyevich Mosharov ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Hypersonic Flow ◽  
Leading Edge ◽  
Turbulent Transition ◽  
Laminar Turbulent Transition
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