Relationship between the instability waves and noise of high-speed jets

AIAA Journal ◽  
1992 ◽  
Vol 30 (7) ◽  
pp. 1747-1752 ◽  
Author(s):  
Christopher K. W. Tam ◽  
Ping Chen ◽  
J. M. Seiner
Keyword(s):  
High Speed ◽  
Instability Waves

On the three families of instability waves of high-speed jets

1989 ◽  
Vol 201 (-1) ◽  
pp. 447 ◽  
Author(s):  
Christopher K. W. Tam ◽  
Fang Q. Hu
Keyword(s):  
High Speed ◽  
Instability Waves

scholarly journals Cavity surface wave patterns and general appearance

1970 ◽  
Vol 44 (1) ◽  
pp. 33-49 ◽  
Author(s):  
Christopher Brennen
Keyword(s):  
Boundary Layer ◽  
Surface Wave ◽  
High Speed ◽  
Cavity Surface ◽  
High Speed Photography ◽  
Instability Analysis ◽  
Instability Waves ◽  
Spatial Growth ◽  
Wave Patterns ◽  
General Appearance

Observations were made of the appearance of hydrodynamic cavities behind a series of axisymmetric headforms. Among the phenomena investigated was the transition of the interfacial or separated boundary layer on the cavity surface. The first stage of this process, namely the spatial growth of instability waves could be distinguished by means of high-speed photography. Comparison is made with a theoretical instability analysis.

Measurements of axial instability waves in the near exit region of a high speed liquid jet

2011 ◽  
Vol 23 (12) ◽  
pp. 124105 ◽  
Author(s):  
J. E. Portillo ◽  
S. H. Collicott ◽  
G. A. Blaisdell
Keyword(s):  
High Speed ◽  
Liquid Jet ◽  
Instability Waves ◽  
Exit Region

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.

Radiation from large-scale structures within a turbulent shear layer

2018 ◽  
Vol 17 (4-5) ◽  
pp. 541-570
Author(s):  
Steven AE Miller ◽  
Weiqi Shen
Keyword(s):  
High Speed ◽  
Large Scale ◽  
Turbulence Modeling ◽  
Acoustic Radiation ◽  
Base Flow ◽  
Navier Stokes ◽  
Turbulent Shear ◽  
Acoustic Analogy ◽  
Previous Theory ◽  
Instability Waves

We examine the acoustic radiation from multiple high-speed subsonic and supersonic free shear layers. We decompose the flow field into a base component (an average), a component associated with the spatially and temporarily growing and decaying instability waves, and the acoustic radiation associated from the instability waves. We find an analytical solution for the acoustic radiation through the use of an acoustic analogy. The arguments of the acoustic analogy involve the two-point cross-correlation of quantities associated with the base flow and instability waves. The instability waves are modeled with a newly proposed basis function. A combination of large eddy simulation, steady Reynolds-averaged Navier–Stokes solutions, and turbulence modeling is used to close the acoustic model. We compare our predictions to those of previous investigators and our predictions match previous theory. We find that the dominant acoustic radiation is due to the large-scale highly spatially coherent turbulence. The interaction of the instability waves causes secondary broadband radiation at higher observer angles.

Microfabrication research at the National Submicron Facility

1983 ◽  
Vol 41 ◽  
pp. 86-89
Author(s):  
E.D. Wolf
Keyword(s):  
Integrated Circuits ◽  
Particle Physics ◽  
High Speed ◽  
New Technology ◽  
High Energy ◽  
High Energy Particle ◽  
New Science ◽  
Wide Range ◽  
Intermediate Domain ◽  
Circuit Function

Most microelectronics devices and circuits operate faster, consume less power, execute more functions and cost less per circuit function when the feature-sizes internal to the devices and circuits are made smaller. This is part of the stimulus for the Very High-Speed Integrated Circuits (VHSIC) program. There is also a need for smaller, more sensitive sensors in a wide range of disciplines that includes electrochemistry, neurophysiology and ultra-high pressure solid state research. There is often fundamental new science (and sometimes new technology) to be revealed (and used) when a basic parameter such as size is extended to new dimensions, as is evident at the two extremes of smallness and largeness, high energy particle physics and cosmology, respectively. However, there is also a very important intermediate domain of size that spans from the diameter of a small cluster of atoms up to near one micrometer which may also have just as profound effects on society as “big” physics.

Vacuum System to Minimize the Specimen Contamination of High-Performance EM

1977 ◽  
Vol 35 ◽  
pp. 68-69
Author(s):  
N. Yoshimura ◽  
K. Shirota ◽  
T. Etoh
Keyword(s):  
Electron Microscope ◽  
High Speed ◽  
High Performance ◽  
High Vacuum ◽  
Vacuum System ◽  
Pump System ◽  
Pumping System ◽  
Diffusion Pump ◽  
Almost All ◽  
Cascade Type

One of the most important requirements for a high-performance EM, especially an analytical EM using a fine beam probe, is to prevent specimen contamination by providing a clean high vacuum in the vicinity of the specimen. However, in almost all commercial EMs, the pressure in the vicinity of the specimen under observation is usually more than ten times higher than the pressure measured at the punping line. The EM column inevitably requires the use of greased Viton O-rings for fine movement, and specimens and films need to be exchanged frequently and several attachments may also be exchanged. For these reasons, a high speed pumping system, as well as a clean vacuum system, is now required. A newly developed electron microscope, the JEM-100CX features clean high vacuum in the vicinity of the specimen, realized by the use of a CASCADE type diffusion pump system which has been essentially improved over its predeces- sorD employed on the JEM-100C.

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