Measurements and Computations of Second-Mode Instability Waves in Several Hypersonic Wind Tunnels

2010 ◽  
Author(s):  
Dennis Berridge ◽  
Katya Casper ◽  
Shann Rufer ◽  
Christopher Alba ◽  
Daniel Lewis ◽  
...  
Keyword(s):  
Wind Tunnels ◽  
Mode Instability ◽  
Instability Waves ◽  
Second Mode

Experimental study of second-mode instability growth and breakdown in a hypersonic boundary layer using high-speed schlieren visualization

2016 ◽  
Vol 797 ◽  
pp. 471-503 ◽  
Author(s):  
S. J. Laurence ◽  
A. Wagner ◽  
K. Hannemann
Keyword(s):  
Boundary Layer ◽  
High Speed ◽  
Porous Ceramic ◽  
Propagation Speed ◽  
Mode Instability ◽  
Instability Waves ◽  
Local Maxima ◽  
High Enthalpy ◽  
Reflected Shock ◽  
Second Mode

Visualization experiments are performed to investigate the development of instability waves within the boundary layer on a slender cone under high Mach number conditions. The experimental facility is a reflected-shock wind tunnel, allowing both low (Mach-8 flight equivalent) and high-enthalpy conditions to be simulated. Second-mode instability waves are visualized using a high-speed schlieren set-up, with pulse bursting of the light source allowing the propagation speed of the wavepackets to be unambiguously resolved. This, in combination with wavelength information derived from the images, enables the calculation of the disturbance frequencies. At the lower-enthalpy conditions, we concentrate on the late laminar and transitional regions of the flow. General characteristics are revealed through time-resolved and ensemble-averaged spectra on both smooth and porous ceramic surfaces of the cone. Analysis of the development of individual wavepackets is then performed. It is found that the wavepacket structures evolve from a ‘rope-like’ appearance to become more interwoven as the disturbance nears breakdown. The wall-normal disturbance distributions of both the fundamental and first harmonic, which initially have local maxima at the wall and near $y/{\it\delta}=0.7$–0.75, exhibit an increase in signal energy close to the boundary-layer edge during this evolution. The structure angle of the disturbances also undergoes subtle changes as the wavepacket develops prior to breakdown. Experiments are also performed at high-enthalpy ($h_{0}\approx 12~\text{MJ}~\text{kg}^{-1}$) conditions in the laminar regime, and the visualization technique is shown to be capable of resolving wavepacket propagation speeds and frequencies at such conditions. The visualizations reveal a somewhat different wall-normal distribution to the low-enthalpy case, with the disturbance energy concentrated much more towards the wall. This is attributed to the highly cooled nature of the wall at high enthalpy.

Simulation of Second-Mode Instability in a Real-Gas Hypersonic Flow with Graphite Ablation

AIAA Journal ◽  
2014 ◽  
Vol 52 (8) ◽  
pp. 1632-1652 ◽  
Author(s):  
Clifton H. Mortensen ◽  
Xiaolin Zhong
Keyword(s):  
Hypersonic Flow ◽  
Mode Instability ◽  
Real Gas ◽  
Second Mode

scholarly journals Linear, nonlinear and transitional regimes of second-mode instability

2020 ◽  
Vol 905 ◽  
Author(s):  
S. Unnikrishnan ◽  
Datta V. Gaitonde
Keyword(s):  
Mode Instability ◽  
Second Mode

Abstract

scholarly journals On the mechanism by which nose bluntness suppresses second-mode instability

2020 ◽  
Vol 10 (4) ◽  
pp. 230-240 ◽  
Author(s):  
Armani Batista ◽  
Arham Amin Khan ◽  
Joseph Kuehl
Keyword(s):  
Mode Instability ◽  
Second Mode

Numerical and experimental analysis of the first-and second-mode instability in a rotor-bearing system

2013 ◽  
Vol 84 (4) ◽  
pp. 519-541 ◽  
Author(s):  
Hui Ma ◽  
Hui Li ◽  
Heqiang Niu ◽  
Rongze Song ◽  
Bangchun Wen
Keyword(s):  
Experimental Analysis ◽  
Mode Instability ◽  
Second Mode ◽  
Rotor Bearing ◽  
Bearing System

Instability of rectangular jets

1993 ◽  
Vol 248 ◽  
pp. 425-448 ◽  
Author(s):  
Christopher K. W. Tam ◽  
Andrew T. Thies
Keyword(s):  
Pressure Fluctuations ◽  
Vortex Sheet ◽  
Mode Shapes ◽  
Instability Wave ◽  
Instability Waves ◽  
Wave Characteristics ◽  
Linearly Independent ◽  
Second Mode ◽  
Independent Families ◽  
The Stability

The instability of rectangular jets is investigated using a vortex-sheet model. It is shown that such jets support four linearly independent families of instability waves. Within each family there are infinitely many modes. A way to classify these modes according to the characteristics of their mode shapes or eigenfunctions is proposed. The stability equation for jets of this geometry is non-separable so that the traditional methods of analysis are not applicable. It is demonstrated that the boundary element method can be used to calculate the dispersion relations and eigenfunctions of these instability wave modes. The method is robust and efficient. A parametric study of the instability wave characteristics has been carried out. A sample of the numerical results is reported here. It is found that the first and third modes of each instability wave family are corner modes. The pressure fluctuations associated with these instability waves are localized near the corners of the jet. The second mode, however, is a centre mode with maximum fluctuations concentrated in the central portion of the jet flow. The centre mode has the largest spatial growth rate. It is anticipated that as the instability waves propagate downstream the centre mode would emerge as the dominant instability of the jet.

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