scholarly journals Sensitivity analysis for subsonic jet using adjoint of non local stability equations

2015 ◽  
Author(s):  
Christophe Airiau ◽  
Tobias Ansaldi
Keyword(s):  
Sensitivity Analysis ◽  
Local Stability ◽  
Non Local ◽  
Subsonic Jet

scholarly journals Sensitivity analysis of non‐local damage in soft biological tissues

2020 ◽  
Author(s):  
Di Zuo ◽  
Stéphane Avril ◽  
Chunjiang Ran ◽  
Haitian Yang ◽  
S. Jamaleddin Mousavi ◽  
...  
Keyword(s):  
Sensitivity Analysis ◽  
Biological Tissues ◽  
Local Damage ◽  
Soft Biological Tissues ◽  
Non Local

Sensitivity analysis of a non‐local, gradient enhanced damage model

PAMM ◽  
2018 ◽  
Vol 18 (1) ◽  
Author(s):  
Fabian Guhr ◽  
Franz‐Joseph Barthold ◽  
Andreas Menzel ◽  
Leon Sprave ◽  
Jan Liedmann
Keyword(s):  
Sensitivity Analysis ◽  
Damage Model ◽  
Non Local ◽  
Local Gradient

scholarly journals On non-local stability properties of extremum seeking control

Automatica ◽  
2006 ◽  
Vol 42 (6) ◽  
pp. 889-903 ◽  
Author(s):  
Ying Tan ◽  
Dragan Nešić ◽  
Iven Mareels
Keyword(s):  
Local Stability ◽  
Extremum Seeking ◽  
Extremum Seeking Control ◽  
Stability Properties ◽  
Non Local

Adjoint Sensitivity Analysis of Hydrodynamic Stability in a Gas Turbine Fuel Injector

2015 ◽  
Author(s):  
Outi Tammisola ◽  
Matthew P. Juniper
Keyword(s):  
Growth Rate ◽  
Sensitivity Analysis ◽  
Combustion Chamber ◽  
Gas Turbine ◽  
Local Stability ◽  
Recirculation Zone ◽  
Base Flow ◽  
Fuel Injector ◽  
Mean Flow ◽  
Thermoacoustic Instability

Hydrodynamic oscillations in gas turbine fuel injectors help to mix the fuel and air but can also contribute to thermoacoustic instability. Small changes to some parts of a fuel injector greatly affect the frequency and amplitude of these oscillations. These regions can be identified efficiently with adjoint-based sensitivity analysis. This is a linear technique that identifies the region of the flow that causes the oscillation, the regions of the flow that are most sensitive to external forcing, and the regions of the flow that, when altered, have most influence on the oscillation. In this paper, we extend this to the flow from a gas turbine’s single stream radial swirler, which has been extensively studied experimentally (GT2008-50278) [8]. The swirling annular flow enters the combustion chamber and expands to the chamber walls, forming a conical recirculation zone along the centreline and an annular recirculation zone in the upstream corner. In this study, the steady base flow and the stability analysis are calculated at Re 200–3800 based on the mean flow velocity and inlet diameter. The velocity field is similar to that found from experiments and LES, and the local stability results are close to those at higher Re (GT2012-68253) [11]. All the analyses (experiments, LES, uRANS, local stability, and the global stability in this paper) show that a helical motion develops around the central recirculation zone. This develops into a precessing vortex core. The adjoint-based sensitivity analysis reveals that the frequency and growth rate of the oscillation is dictated by conditions just upstream of the central recirculation zone (the wavemaker region). It also reveals that this oscillation is very receptive to forcing at the sharp edges of the injector. In practical situations, this forcing could arise from an impinging acoustic wave, showing that these edges could be influential in the feedback mechanism that causes thermoacoustic instability. The analysis also shows how the growth rate and frequency of the oscillation change with either small shape changes of the nozzle, or additional suction or blowing at the walls of the injector. It reveals that the oscillations originate in a very localized region at the entry to the combustion chamber, which lies near the separation point at the outer inlet, and extends to the outlet of the inner pipe. Any scheme designed to control the frequency and amplitude of the oscillation only needs to change the flow in this localized region.

Toward High-Resolution Low-Voltage SEM

1988 ◽  
Vol 46 ◽  
pp. 218-219
Author(s):  
Zhifeng Shao
Keyword(s):  
Low Voltage ◽  
Spherical Aberration ◽  
Chromatic Aberration ◽  
Limiting Factor ◽  
Operating Voltage ◽  
Probe Radius ◽  
Non Local ◽  
Electron Microscopes ◽  
Image Position ◽  
Scanning Electron Microscopes

Recently, low voltage (≤5kV) scanning electron microscopes have become popular because of their unprecedented advantages, such as minimized charging effects and smaller specimen damage, etc. Perhaps the most important advantage of LVSEM is that they may be able to provide ultrahigh resolution since the interaction volume decreases when electron energy is reduced. It is obvious that no matter how low the operating voltage is, the resolution is always poorer than the probe radius. To achieve 10Å resolution at 5kV (including non-local effects), we would require a probe radius of 5∽6 Å. At low voltages, we can no longer ignore the effects of chromatic aberration because of the increased ratio δV/V. The 3rd order spherical aberration is another major limiting factor. The optimized aperture should be calculated as

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