Effect of pressure gradient on the stability of hypersonic boundary layer flows

2017 ◽  
Author(s):  
Jie Ren ◽  
Song Fu
Keyword(s):  
Boundary Layer ◽  
Pressure Gradient ◽  
Hypersonic Boundary Layer ◽  
Boundary Layer Flows ◽  
Effect Of Pressure ◽  
The Stability

On the impulse response for swept boundary-layer flows

1997 ◽  
Vol 344 ◽  
pp. 317-334 ◽  
Author(s):  
R. J. LINGWOOD
Keyword(s):  
Boundary Layer ◽  
Pressure Gradient ◽  
Boundary Layers ◽  
Three Dimensional ◽  
Boundary Layer Flows ◽  
Flow Angle ◽  
Laminar Boundary Layers ◽  
Turbulent Transition ◽  
Convective Process ◽  
The Stability

Swept-wedge flows are used to study the effects of pressure gradient and flow angle on the stability of three-dimensional laminar boundary layers. It is shown that the flow is absolutely unstable in the chordwise direction, i.e. disturbances grow in time at every chordwise location, for certain parameter combinations. However, laminar–turbulent transition may still be a convective process.

Transition of streamwise streaks in zero-pressure-gradient boundary layers

2002 ◽  
Vol 472 ◽  
pp. 229-261 ◽  
Author(s):  
LUCA BRANDT ◽  
DAN S. HENNINGSON
Keyword(s):  
Boundary Layer ◽  
Pressure Gradient ◽  
High Speed ◽  
Plate Boundary ◽  
Transition Process ◽  
Free Stream Turbulence ◽  
Tollmien Schlichting ◽  
Streamwise Streaks ◽  
The Stability ◽  
Optimal Disturbances

A transition scenario initiated by streamwise low- and high-speed streaks in a flat-plate boundary layer is studied. In many shear flows, the perturbations that show the highest potential for transient energy amplification consist of streamwise-aligned vortices. Due to the lift-up mechanism these optimal disturbances lead to elongated streamwise streaks downstream, with significant spanwise modulation. In a previous investigation (Andersson et al. 2001), the stability of these streaks in a zero-pressure-gradient boundary layer was studied by means of Floquet theory and numerical simulations. The sinuous instability mode was found to be the most dangerous disturbance. We present here the first simulation of the breakdown to turbulence originating from the sinuous instability of streamwise streaks. The main structures observed during the transition process consist of elongated quasi-streamwise vortices located on the flanks of the low-speed streak. Vortices of alternating sign are overlapping in the streamwise direction in a staggered pattern. The present scenario is compared with transition initiated by Tollmien–Schlichting waves and their secondary instability and by-pass transition initiated by a pair of oblique waves. The relevance of this scenario to transition induced by free-stream turbulence is also discussed.

Stability of a hypersonic boundary layer with a pressure gradient

2000 ◽  
Vol 45 (4) ◽  
pp. 179-182
Author(s):  
V. M. Fomin ◽  
A. A. Maslov ◽  
A. A. Sidorenko ◽  
A. N. Shiplyuk
Keyword(s):  
Boundary Layer ◽  
Pressure Gradient ◽  
Hypersonic Boundary Layer

An experiment on the stability of hypersonic laminar boundary layers

1960 ◽  
Vol 7 (3) ◽  
pp. 385-396 ◽  
Author(s):  
Anthony Demetriades
Keyword(s):  
Boundary Layer ◽  
Flat Surface ◽  
Hypersonic Boundary Layer ◽  
Natural Disturbances ◽  
Hot Wire ◽  
Amplitude Variation ◽  
Laminar Boundary Layers ◽  
Boundary Layer Instability ◽  
The Stability ◽  
Maximum Amplification

An experimental investigation of the hydrodynamic stability of the laminar hypersonic boundary layer was carried out with the aid of a hot-wire anemometer. The case investigated was that of a flat surface at zero angle of attack and no heat transfer.The streamwise amplitude variation of both natural disturbances and of disturbances artifically excited with a siren mechanism was studied. In both cases it was found that such small fluctuations amplify for certain ranges of frequency and Reynolds number Rθ, and damp for others. The demarcation boundaries for the amplification (instability) zone were found to resemble the corresponding limits of boundary-layer instability at lower speeds. A ‘line of maximum amplification’ of disturbances was also found. The amplification rates and hence the degree of selectivity of the hypersonic layer were found, however, to be considerably lower than those at the lower speeds. The disturbances selected by the layer for maximum amplifications have a wavelength which was estimated to be about twenty times the boundary-layer thickness δ.

Effect of pressure gradient in the connection region on the stability of the edge pedestal

2020 ◽  
Vol 60 (7) ◽  
pp. 076022
Author(s):  
S.K. Kim ◽  
S. Saarelma ◽  
Y.-S. Na ◽  
O. Kwon
Keyword(s):  
Pressure Gradient ◽  
Effect Of Pressure ◽  
The Stability

scholarly journals Investigation of the Calmed Region Behind a Turbulent Spot

1996 ◽  
Author(s):  
J. P. Gostelow ◽  
G. J. Walker ◽  
W. J. Solomon ◽  
G. Hong ◽  
N. Melwani
Keyword(s):  
Boundary Layer ◽  
Pressure Gradient ◽  
Axial Flow ◽  
Adverse Pressure Gradient ◽  
Turbulent Spot ◽  
Boundary Layer Flows ◽  
Turbulent Spots ◽  
Turbulent Layer ◽  
Controlled Diffusion ◽  
Flow Compressor

Measurements are presented of the calmed region behind triggered wave packets and turbulent spots under a controlled diffusion adverse pressure gradient in a wind tunnel. Similar measurements are also presented from the stator blades of an axial flow compressor, where turbulent spots are induced by the passing of rotor wakes. The purpose is to gain an appreciation of turbulent spot behavior under a strong adverse pressure gradient as a foundation for the more accurate modeling of spots and their environment in predictions of transitional boundary layer flows. Under an adverse pressure gradient the calmed region behind the spot is extensive; its interaction with the surrounding turbulent layer is complex and is dependent on whether the surrounding natural boundary layer is laminar or turbulent. Some insights are gleaned concerning the behavior of the calmed region which will subsequently be used in attempts to model the calmed region. Although these fundamental investigations of the calmed region have been extensive much remains to be understood.

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