Extracting Information on Linear and Nonlinear Absorption from Two-Beam Action Spectroscopy Data

2019 ◽  
Vol 123 (33) ◽  
pp. 7314-7322 ◽  
Author(s):  
Samuel R. Cohen ◽  
John T. Fourkas
Author(s):  
Scott Webster ◽  
Jie Fu ◽  
Olga V. Przhonska ◽  
Lazaro A. Padilha ◽  
David J. Hagan ◽  
...  

2002 ◽  
Vol 285 (2-3) ◽  
pp. 207-220 ◽  
Author(s):  
Patrick Norman ◽  
Peter Cronstrand ◽  
Jerry Ericsson

1992 ◽  
Vol 247 ◽  
Author(s):  
Christopher S. Winter ◽  
S. N. Oliver ◽  
C A. S. Hill

ABSTRACTThe nonlinear refractive index, linear and nonlinear absorption coefficients of a number of nickel dithiolene-doped PMMA polymers have been measured. Nonlinear refractive indices up to about 10−8 cm−2/KW were observed, with figures of merit defined by δnsat/αλ and Reχ(3) / Im χ(3) within acceptable device limits.


Author(s):  
Maryam Hatamimoslehabadi ◽  
Mathieu Frenette ◽  
Stephanie Bellinger-Buckley ◽  
Jefffrey La ◽  
Esraa Ahmad ◽  
...  

Author(s):  
Jochen Rupp ◽  
Jon Carrotte ◽  
Adrian Spencer

Gas turbine combustion systems are prone to thermo-acoustic instabilities, and this is particularly the case for new low emission lean burn type systems. The presence of such instabilities is basically a function of the unsteady heat release within the system (i.e., both magnitude and phase) and the amount of damping. This paper is concerned with this latter process and the potential damping provided by perforated liners and other circular apertures found within gas turbine combustion systems. In particular, the paper outlines experimental measurements that characterize the flow field within the near field region of circular apertures when being subjected to incident acoustic pressure fluctuations. In this way the fundamental process by which acoustic energy is converted into kinetic energy of the velocity field can be investigated. Experimental results are presented for a single orifice located in an isothermal duct at ambient test conditions. Attached to the duct are two loudspeakers that provide pressure fluctuations incident onto the orifice. Unsteady pressure measurements enable the acoustic power absorbed by the orifice to be determined. This was undertaken for a range of excitation amplitudes and mean flows through the orifice. In this way regimes where both linear and nonlinear absorption occur along with the transition between these regimes can be investigated. The key to designing efficient passive dampers is to understand the interaction between the unsteady velocity field, generated at the orifice and the acoustic pressure fluctuations. Hence experimental techniques are also presented that enable such detailed measurements of the flow field to be made using particle image velocimetry. These measurements were obtained for conditions at which linear and nonlinear absorption was observed. Furthermore, proper orthogonal decomposition was used as a novel analysis technique for investigating the unsteady coherent structures responsible for the absorption of energy from the acoustic field.


2019 ◽  
Vol 59 ◽  
pp. 465-472 ◽  
Author(s):  
Hüseyin Ertap ◽  
Mustafa Yuksek ◽  
Ahmet Karatay ◽  
Ayhan Elmali ◽  
Mevlut Karabulut

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