scholarly journals Linear instability of the Peregrine breather: Numerical and analytical investigations

2019 ◽  
Vol 141 ◽  
pp. 36-43 ◽  
Author(s):  
A. Calini ◽  
C.M. Schober ◽  
M. Strawn
Keyword(s):  
Linear Instability ◽  
Peregrine Breather

Linear instability of an annular liquid jet with gas velocity oscillations

2021 ◽  
Vol 33 (5) ◽  
pp. 054110
Author(s):  
Xin-yan Guan ◽  
Bo-qi Jia ◽  
Li-jun Yang ◽  
Qing-fei Fu
Keyword(s):  
Linear Instability ◽  
Liquid Jet ◽  
Gas Velocity ◽  
Annular Liquid Jet

scholarly journals Optimal Stability Thresholds in Rotating Fully Anisotropic Porous Medium with LTNE

2021 ◽  
Author(s):  
Florinda Capone ◽  
Maurizio Gentile ◽  
Jacopo A. Gianfrani
Keyword(s):  
Porous Layer ◽  
Nonlinear Stability ◽  
Steady Motion ◽  
Vertical Axis ◽  
Linear Instability ◽  
List Type ◽  
Nonlinear Stability Analysis ◽  
Onset Of Convection ◽  
Anisotropic Porous Medium ◽  
Necessary And Sufficient

Abstract The onset of thermal convection in an anisotropic horizontal porous layer heated from below and rotating about vertical axis, under local thermal non-equilibrium hypothesis is studied. Linear and nonlinear stability analysis of the conduction solution is performed. Coincidence between the linear instability and the global nonlinear stability thresholds with respect to the L2—norm is proved. Article Highlights A necessary and sufficient condition for the onset of convection in a rotating anisotropic porous layer has been obtained. It has been proved that convection can occur only through a steady motion. A detailed proof is reported thoroughly. Numerical analysis shows that permeability promotes convection, while thermal conductivities and rotation stabilize conduction.

Linear instability characteristics of wake‐shear layers

1992 ◽  
Vol 4 (1) ◽  
pp. 189-191 ◽  
Author(s):  
D. Wallace ◽  
L. G. Redekopp
Keyword(s):  
Shear Layers ◽  
Linear Instability

Front instability in a condensed phase combustion model

2015 ◽  
Vol 4 (3) ◽  
pp. 153-176 ◽  
Author(s):  
Alexis Bonnet ◽  
Fathi Dkhil ◽  
Elisabeth Logak
Keyword(s):  
Activation Energy ◽  
Condensed Phase ◽  
Linear Instability ◽  
Combustion Model ◽  
Energy Limit ◽  
High Activation ◽  
Front Solution ◽  
High Activation Energy ◽  
Linearized Problem ◽  
Existence Of Zeros

AbstractWe consider a condensed phase (or solid) combustion model and its linearization around the travelling front solution. We construct an Evans function to characterize the eigenvalues of the linearized problem. We estimate this functional in the high activation energy limit. We deduce the existence of zeros with nonnegative real part for high activation energy, which proves the linear instability of the travelling front solution.

scholarly journals An evaluation of linear instability waves as sources of sound in a supersonic turbulent jet

2002 ◽  
Vol 14 (10) ◽  
pp. 3593-3600 ◽  
Author(s):  
Kamran Mohseni ◽  
Tim Colonius ◽  
Jonathan B. Freund
Keyword(s):  
Linear Instability ◽  
Turbulent Jet ◽  
Instability Waves

Exploitation of Subharmonics for Separated Shear Layer Control on a High-Lift Low-Pressure Turbine Using Acoustic Forcing

2013 ◽  
Vol 136 (5) ◽  
Author(s):  
Chiara Bernardini ◽  
Stuart I. Benton ◽  
Jen-Ping Chen ◽  
Jeffrey P. Bons
Keyword(s):  
Shear Layer ◽  
Separation Bubble ◽  
Boundary Layer Separation ◽  
Low Pressure ◽  
Linear Instability ◽  
Laminar Separation ◽  
Significant Control ◽  
Low Pressure Turbine ◽  
Separated Shear Layer ◽  
Sound Control

The mechanism of separation control by sound excitation is investigated on the aft-loaded low-pressure turbine (LPT) blade profile, the L1A, which experiences a large boundary layer separation at low Reynolds numbers. Previous work by the authors has shown that on a laminar separation bubble such as that experienced by the front-loaded L2F profile, sound excitation control has its best performance at the most unstable frequency of the shear layer due to the exploitation of the linear instability mechanism. The different loading distribution on the L1A increases the distance of the separated shear layer from the wall and the exploitation of the same linear mechanism is no longer effective in these conditions. However, significant control authority is found in the range of the first subharmonic of the natural unstable frequency. The amplitude of forced excitation required for significant wake loss reduction is higher than that needed when exploiting linear instability, but unlike the latter case, no threshold amplitude is found. The fluid-dynamics mechanisms under these conditions are investigated by particle image velocimetry (PIV) measurements. Phase-locked PIV data gives insight into the growth and development of structures as they are shed from the shear layer and merge to lock into the excited frequency. Unlike near-wall laminar separation sound control, it is found that when such large separated shear layers occur, sound excitation at subharmonics of the fundamental frequency is still effective with high-Tu levels.

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