Identification of Instability Waves in High-Speed Turbulent Jets

2007 ◽  
Author(s):  
Jaiyoung Ryu ◽  
Sanjiva Lele ◽  
K. Viswanathan
Keyword(s):  
High Speed ◽  
Turbulent Jets ◽  
Instability Waves

Active control of instability waves in excited and nonexcited turbulent jets

2017 ◽  
Author(s):  
Victor Kopiev ◽  
Georgy Faranosov ◽  
Oleg Bychkov ◽  
Mikhail Zaytsev ◽  
Vladimir Kopiev ◽  
...  
Keyword(s):  
Active Control ◽  
Turbulent Jets ◽  
Instability Waves

Low-frequency sound sources in high-speed turbulent jets

2008 ◽  
Vol 617 ◽  
pp. 231-253 ◽  
Author(s):  
DANIEL J. BODONY ◽  
SANJIVA K. LELE
Keyword(s):  
High Speed ◽  
Low Frequency ◽  
Turbulent Jets ◽  
Acoustic Analogy ◽  
Sound Sources ◽  
Strongly Coupled ◽  
Eddy Simulation ◽  
Phase Cancellation ◽  
Jet Velocity ◽  
Two Jets

An analysis of the sound radiated by three turbulent, high-speed jets is conducted using Lighthill's acoustic analogy (Proc. R. Soc. Lond. A, vol. 211, 1952, p. 564). Computed by large eddy simulation the three jets operate at different conditions: a Mach 0.9 cold jet, a Mach 2.0 cold jet and a Mach 1.0 heated jet. The last two jets have the same jet velocity and differ only by temperature. None of the jets exhibit Mach wave characteristics. For these jets the comparison between the Lighthill-predicted sound and the directly computed sound is favourable for all jets and for the two angles (30° and 90°, measured from the downstream jet axis) considered. The momentum (ρuiuj) and the so-called entropy [p − p∞ − a∞2(ρ − ρ∞)] contributions are examined in the acoustic far field. It is found that significant phase cancellation exists between the momentum and entropy components. It is observed that for high-speed jets one cannot consider ρuiuj and (p′ − a∞2ρ′)δij as independent sources. In particular the ρ′ūxūx component of ρuiuj is strongly coupled with the entropy term as a consequence of compressibility and the high jet velocity and not because of a linear sound-generation mechanism. Further, in more usefully decoupling the momentum and entropic contributions, the decomposition of Tij due to Lilley (Tech. Rep. AGARD CP-131 1974) is preferred. Connections are made between the present results and the quieting of high-speed jets with heating.

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 growth and propagation of linear instability waves in compressible turbulent jets

2009 ◽  
Vol 21 (5) ◽  
pp. 054106 ◽  
Author(s):  
Prasun K. Ray ◽  
Lawrence C. Cheung ◽  
Sanjiva K. Lele
Keyword(s):  
Turbulent Jets ◽  
Linear Instability ◽  
Instability Waves

Meandering due to large eddies and the statistically self-similar dynamics of quasi-two-dimensional jets

2012 ◽  
Vol 692 ◽  
pp. 347-368 ◽  
Author(s):  
Julien R. Landel ◽  
C. P. Caulfield ◽  
Andrew W. Woods
Keyword(s):  
Vertical Velocity ◽  
High Speed ◽  
Turbulent Jets ◽  
Theoretical Models ◽  
Maximum Speed ◽  
Two Dimensional ◽  
The Core ◽  
Self Similar ◽  
The Mean ◽  
Large Eddies

AbstractWe investigate experimentally the structure of quasi-two-dimensional plane turbulent jets discharged vertically from a slot of width $d$ into a fluid confined between two relatively close rigid boundaries with gap $W\ensuremath{\sim} O(d)$. At large vertical distances $z\gg W$ the jet structure consists of a meandering core with large counter-rotating eddies, which develop on alternate sides of the core. Using particle image velocimetry, we observe an inverse cascade typical of quasi-two-dimensional turbulence where both the core and the eddies grow linearly with $z$ and travel at an average speed proportional to ${z}^{\ensuremath{-} 1/ 2} $. However, although the present study concerns quasi-two-dimensional confined jets, the jets are self-similar and the mean properties are consistent with both experimental results and theoretical models of the time-averaged properties of fully unconfined planar two-dimensional jets. We believe that the dynamics of the interacting core and large eddies accounts for the Gaussian profile of the mean vertical velocity as shown by the spatial statistical distribution of the core and eddy structure. The lateral excursions (caused by the propagating eddies) of this high-speed central core produce a Gaussian distribution for the time-averaged vertical velocity. In addition, we find that approximately 75 % of the total momentum flux of the jet is contained within the core. The eddies travel substantially slower (at approximately 25 % of the maximum speed of the core) at each height and their growth is primarily attributed to entrainment of ambient fluid. The frequency of occurrence of the eddies decreases in a stepwise manner due to merging, with a well-defined minimum value of the corresponding Strouhal number $\mathit{St}\geq 0. 07$.

scholarly journals Sensitivity of wavepackets in jets to nonlinear effects: the role of the critical layer

2016 ◽  
Vol 811 ◽  
pp. 95-137 ◽  
Author(s):  
Gilles Tissot ◽  
Mengqi Zhang ◽  
Francisco C. Lajús ◽  
André V. G. Cavalieri ◽  
Peter Jordan
Keyword(s):  
Linear Models ◽  
Nonlinear Effects ◽  
Turbulent Jets ◽  
Building Blocks ◽  
Linear Instability ◽  
Critical Layer ◽  
Potential Core ◽  
Instability Waves ◽  
Reduced Order ◽  
Modelling Framework

Linear instability waves, or wavepackets, are key building blocks for the jet-noise problem. It has been shown in previous work that linear models correctly predict the evolution of axisymmetric wavepackets up to the end of the potential core of subsonic turbulent jets. Beyond this station, linear models fail, and nonlinearity is the likely missing piece. The essential underlying nonlinear mechanisms are unknown, and it remains unclear how these should be incorporated in a reduced-order model. The nonlinear interactions are considered in this work as an ‘external’ harmonic forcing added to the standard linear model. This modelling framework is explored using a locally parallel resolvent analysis to determine optimal forcing and associated responses, and a global approach based on 4D-Var data assimilation aimed at finding the optimal forcing of the parabolised stability equations that would minimise errors in the predictions of wavepackets. In all of the problems considered, the critical layer is found to be relevant: it is the position where sensitivity of wavepackets to nonlinearity is greatest. It is seen that disturbances are forced around the critical layer, and tilted by shear as they are advected, in a manner suggestive of an Orr-like mechanism. The ensemble of results suggests that critical-layer effects play a central role in the dynamics of wavepackets in subsonic turbulent jets, and that inclusion of such effects may remedy the shortcomings of linear reduced-order models.

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
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