Experimental studying the effect of porous coatings of different lengths on second-mode disturbances in a hypersonic boundary layer of sharp and blunted cones

2016 ◽  
Author(s):  
S. V. Lukashevich ◽  
S. O. Morozov ◽  
A. N. Shiplyuk
Keyword(s):  
Boundary Layer ◽  
Hypersonic Boundary Layer ◽  
Porous Coatings ◽  
Second Mode

scholarly journals Stabilization of a hypersonic boundary layer using a felt-metal porous coating

2015 ◽  
Vol 769 ◽  
pp. 729-739 ◽  
Author(s):  
R. C. Tritarelli ◽  
S. K. Lele ◽  
A. Fedorov
Keyword(s):  
Boundary Layer ◽  
Original Work ◽  
Porous Coating ◽  
Hypersonic Boundary Layer ◽  
The Novel ◽  
Porous Coatings ◽  
Hypersonic Boundary Layers ◽  
Second Mode ◽  
Stabilization Effect ◽  
Stability Results

An error in the complex representation of the porous-coating model used in the study by Fedorov et al. (J. Fluid Mech., vol. 479, 2003, pp. 99–124), investigating the stabilization effect of ultrasonically absorptive coatings on hypersonic boundary layers, is pointed out and corrected. This error has been acknowledged by Fedorov et al. (J. Fluid Mech., vol. 769, 2015, pp. 725–728). The corrected version of the erroneous linear stability results of the original work is presented and previously made conclusions are reassessed. The novel numerical results indicate that second-mode instabilities are shifted to lower frequencies on felt-metal porous coatings, similar to the behaviour observed on porous coatings with regular microstructure.

Interactions between second mode and low-frequency waves in a hypersonic boundary layer

2017 ◽  
Vol 820 ◽  
pp. 693-735 ◽  
Author(s):  
Xi Chen ◽  
Yiding Zhu ◽  
Cunbiao Lee
Keyword(s):  
Boundary Layer ◽  
Parametric Resonance ◽  
Low Frequency ◽  
Frequency Mode ◽  
Linear Stability Theory ◽  
Hypersonic Boundary Layer ◽  
Reynolds Stresses ◽  
Second Mode ◽  
Low Frequency Mode ◽  
Low Frequency Waves

The stability of a hypersonic boundary layer on a flared cone was analysed for the same flow conditions as in earlier experiments (Zhang et al., Acta Mech. Sinica, vol. 29, 2013, pp. 48–53; Zhu et al., AIAA J., vol. 54, 2016, pp. 3039–3049). Three instabilities in the flared region, i.e. the first mode, the second mode and the Görtler mode, were identified using linear stability theory (LST). The nonlinear-parabolized stability equations (NPSE) were used in an extensive parametric study of the interactions between the second mode and the single low-frequency mode (the Görtler mode or the first mode). The analysis shows that waves with frequencies below 30 kHz are heavily amplified. These low-frequency disturbances evolve linearly at first and then abruptly transition to parametric resonance. The parametric resonance, which is well described by Floquet theory, can be either a combination resonance (for non-zero frequencies) or a fundamental resonance (for steady waves) of the secondary instability. Moreover, the resonance depends only on the saturated state of the second mode and is insensitive to the initial low-frequency mode profiles and the streamwise curvature, so this resonance is probably observable in boundary layers over straight cones. Analysis of the kinetic energy transfer further shows that the rapid growth of the low-frequency mode is due to the action of the Reynolds stresses. The same mechanism also describes the interactions between a second-mode wave and a pair of low-frequency waves. The only difference is that the fundamental and combination resonances can coexist. Qualitative agreement with the experimental results is achieved.

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.

Evolution of nonlinear processes in a hypersonic boundary layer on a sharp cone

2008 ◽  
Vol 611 ◽  
pp. 427-442 ◽  
Author(s):  
D. BOUNTIN ◽  
A. SHIPLYUK ◽  
A. MASLOV
Keyword(s):  
Boundary Layer ◽  
Mach Number ◽  
Basic Mechanism ◽  
Hypersonic Boundary Layer ◽  
Nonlinear Interactions ◽  
Nonlinear Processes ◽  
Voltage Fluctuation ◽  
Second Mode ◽  
Sharp Cone ◽  
Second Mode Of Disturbances

Nonlinear processes in a hypersonic boundary layer on a sharp cone are considered using the bicoherence method. The experiments are performed for a Mach number M∞ = 5.95 with introduction of artificial wave packets at the frequency of the second mode. It is shown that the basic mechanism of nonlinear interaction at the location of the maximum r.m.s. voltage fluctuation is the subharmonic resonance; all nonlinear interactions in the maximum r.m.s. voltage fluctuation layer are related to the second mode of disturbances; nonlinear processes above and below that layer are much more intense than those in it. The effect of artificial disturbances on nonlinear interactions in the boundary layer is shown to be insignificant.

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