On the role of spectral resolution in velocity shear layer measurements by Doppler reflectometry

2010 ◽  
Vol 81 (10) ◽  
pp. 10D901 ◽  
Author(s):  
T. Happel ◽  
E. Blanco ◽  
T. Estrada
Keyword(s):  
Shear Layer ◽  
Spectral Resolution ◽  
Velocity Shear

scholarly journals Unique Slow Crack Growth Behavior of Isotactic Polypropylene: The Role of Shear Layer-Spherulites Layer Alternated Structure

Polymers ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 2746
Author(s):  
Mingjin Liu ◽  
Jiaxu Luo ◽  
Jin Chen ◽  
Xueqin Gao ◽  
Qiang Fu ◽  
...  
Keyword(s):  
Shear Layer ◽  
Crack Growth ◽  
Isotactic Polypropylene ◽  
Slow Crack Growth ◽  
Crack Growth Behavior ◽  
Polymer Science ◽  
The Past ◽  
Propagation Behavior ◽  
Crack Propagation Behavior

With the development of polymer science, more attention is being paid to the longevity of polymer products. Slow crack growth (SCG), one of the most important factors that reveal the service life of the products, has been investigated widely in the past decades. Here, we manufactured an isotactic polypropylene (iPP) sample with a novel shear layer–spherulites layer alternated structure using multiflow vibration injection molding (MFVIM). However, the effect of the alternated structure on the SCG behavior has never been reported before. Surprisingly, the results showed that the resistivity of polymer to SCG can be enhanced remarkably due to the special alternated structure. Moreover, this sample shows unique slow crack propagation behavior in contrast to the sample with the same thickness of shear layer, presenting multiple microcracks in the spherulites layer, which can explain the reason of the resistivity improvement of polymer to SCG.

scholarly journals Effects of velocity shear layer on detonation propagation in a supersonic expanding combustor

2021 ◽  
Vol 33 (10) ◽  
pp. 105110
Author(s):  
Jian Dai ◽  
Fei Xu ◽  
Xiaodong Cai ◽  
Yasser Mahmoudi
Keyword(s):  
Shear Layer ◽  
Velocity Shear ◽  
Detonation Propagation

Free surface over a horizontal shear layer: vorticity generation and air entrainment mechanisms

2017 ◽  
Vol 813 ◽  
pp. 1007-1044 ◽  
Author(s):  
Matthieu A. André ◽  
Philippe M. Bardet
Keyword(s):  
Free Surface ◽  
Shear Layer ◽  
Air Entrainment ◽  
Horizontal Shear ◽  
Vortex Instability ◽  
Image Velocimetry ◽  
Planar Laser ◽  
Spatio Temporal ◽  
The Waves

Two air entrainment mechanisms driven by vortex instability are reported in the unstable relaxation of a horizontal shear layer below a free surface. This flow is experimentally investigated by means of planar laser-induced fluorescence (PLIF) and particle image velocimetry (PIV) coupled with surface profilometry. PLIF identifies counter-rotating vortex pairs (CRVP) emanating from the surface following the growth of high steepness two-dimensional millimetre-size waves for Reynolds and Weber numbers based on the momentum thickness of 177 to 222 and 7.59 to 13.9, respectively. High spatio-temporal resolution PIV reveals the role of surface-generated vorticity and flow separation in the highly curved trough of the waves on the injection of a CRVP. Air bubbles are entrapped in the wake of these CRVPs at Reynolds number above 190. PIV data and spanwise PLIF images show two initiation mechanisms: primary vortex instability modulating the spanwise location where the flow separates, resulting in the pinch off of an air ligament, and secondary vortex instability turning a CRVP into$\unicode[STIX]{x1D6FA}$-shaped loops pulling the surface down. Instability wavelengths agree with linear stability analysis, and models for these new air entrainment mechanisms are proposed.

scholarly journals Water Column Stability and the Role of Velocity Shear on a Seasonally Stratified Shelf, Mississippi Bight, Northern Gulf of Mexico

2018 ◽  
Vol 123 (8) ◽  
pp. 5777-5796 ◽  
Author(s):  
Brian Dzwonkowski ◽  
Severine Fournier ◽  
Kyeong Park ◽  
Steven L. Dykstra ◽  
John T. Reager
Keyword(s):  
Gulf Of Mexico ◽  
Water Column ◽  
Velocity Shear ◽  
Northern Gulf Of Mexico ◽  
Water Column Stability

Electrostatic and magnetic fluctuations in the proximity of the velocity shear layer in the TJ‐I tokamak

1992 ◽  
Vol 4 (12) ◽  
pp. 4007-4011 ◽  
Author(s):  
I. García‐Cortés ◽  
M. A. Pedrosa ◽  
C. Hidalgo ◽  
B. Brañas ◽  
T. Estrada ◽  
...  
Keyword(s):  
Shear Layer ◽  
Velocity Shear ◽  
Magnetic Fluctuations

Velocity shear layer measurements by reflectometry in TJ-II plasmas

2006 ◽  
Vol 46 (9) ◽  
pp. S792-S798 ◽  
Author(s):  
T Estrada ◽  
E Blanco ◽  
L Cupido ◽  
M.E Manso ◽  
J Sánchez
Keyword(s):  
Shear Layer ◽  
Velocity Shear

scholarly journals Competing kinematic dynamo mechanisms in rotating convection with shear

2010 ◽  
Vol 6 (S271) ◽  
pp. 239-246 ◽  
Author(s):  
Michael R. E. Proctor ◽  
David W. Hughes
Keyword(s):  
Growth Rates ◽  
Convective Flow ◽  
Flow Fields ◽  
Velocity Shear ◽  
Dynamo Action ◽  
Preliminary Results ◽  
Rotating Convection ◽  
Kinematic Dynamo

AbstractFollowing earlier work by Hughes & Proctor (2009) on the role of velocity shear in convectively driven dynamos, we present preliminary results on the nature of dynamo action due to modified flows derived by filtration from the full convective flow. The results suggest that filtering the flow fields has surprisingly little effect on the dynamo growth rates.

scholarly journals Experimental study of X-ray emission from laser-irradiated planar targets on “Mishen” Facility

1992 ◽  
Vol 10 (4) ◽  
pp. 753-758 ◽  
Author(s):  
V. A. Bolotin ◽  
I. N. Burdonskii ◽  
V. V. Gavrilov ◽  
A. Yu. Gol'tsov ◽  
S. V. Zavyalets ◽  
...  
Keyword(s):  
Experimental Study ◽  
Energy Transfer ◽  
Conversion Efficiency ◽  
Spectral Resolution ◽  
Line Emission ◽  
Laser Pulses ◽  
Temporal Analysis ◽  
Ablation Rate ◽  
X Ray

X-ray emission from planar targets irradiated by 1.054-μm laser pulses was observed with temporal, spatial, and spectral resolution. The main purpose of these measurements was the investigation of energy transfer in multilayer targets and X-ray conversion efficiency. A mass ablation rate was determined from temporal analysis of multicharged ion line emission and a key role of corona X-ray emission in accelerated material preheating was established.

The Role of Nonnormality in Overreflection Theory

2010 ◽  
Vol 67 (8) ◽  
pp. 2547-2558 ◽  
Author(s):  
Nikolaos A. Bakas ◽  
Brian F. Farrell
Keyword(s):  
Shear Layer ◽  
Gravity Waves ◽  
Finite Depth ◽  
Stimulated Emission ◽  
Incoming Wave ◽  
Propagating Waves ◽  
Three Stages ◽  
Orr Mechanism ◽  
Weak Stratification

Abstract The role of nonnormality in the overreflection of gravity waves is investigated. In the limit of weak stratification, wave packets having a critical level inside a shear layer of finite depth are reflected with amplified energy. This process, which exhibits the characteristics of stimulated emission, occurs in three stages: first, the incoming wave enters the shear layer and excites nonpropagating perturbations leaning with and against the shear. Subsequently, the energy of perturbations leaning against the shear grows in a manner similar to energy growth of perturbations in constant shear flows, indicating that the Orr mechanism that is slightly modified by stratification underlies the observed growth. Finally, the amplified perturbations excite propagating waves originating from the vicinity of the shear layer boundary. The role of nonnormality in this process is also investigated from the perspective of the associated nonorthogonality of the modes of the dynamical system. It is found that the incident wave packet projects on nonorthogonal analytic modes having the structure of a downward propagating wave in the far field below the shear layer and overreflection expressed by the interaction among these nonorthogonal modes.

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