A 3D frequency-domain linearised Euler solver based on the Goldstein acoustic analogy equations for the study of nonuniform meanflow propagation effects

2013 ◽  
Author(s):  
Vasily A. Semiletov ◽  
Sergey A. Karabasov
Keyword(s):  
Frequency Domain ◽  
Acoustic Analogy ◽  
Propagation Effects ◽  
Euler Solver

The incomplete reception error in acoustic analogy integral with source time domain algorithm

2019 ◽  
Vol 18 (8) ◽  
pp. 780-797
Author(s):  
Yongfei Mu ◽  
Jie Li
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Acoustic Signal ◽  
Processing Method ◽  
Acoustic Analogy ◽  
Time Step ◽  
Retarded Time ◽  
Comparison Results ◽  
Numerical Oscillations ◽  
The Difference

There are two algorithms to solve the retarded time equation in the acoustic analogy. One is the classic retarded time method, and the other is the source time domain algorithm or the advanced time approach. The latter is more effective and simple than the former. However, difficulties may arise in the reconstruction of the acoustic signal in the observer time domain. The signal interpolation in every observer time step and a completeness check at the end are necessary for the reconstruction. In addition, two error regions which cannot to be ignored in frequency domain are generated by the latter. They are called the incomplete reception error. It is the main purpose of present work to analyze the formation process and characteristics of the incomplete reception error. Then the analysis is tested with a simplified model and the numerical results show that there are some spurious numerical oscillations in frequency domain if the incomplete reception regions are not removed. Finally, the difference between the method of directly removing the incomplete reception regions and the standard acoustic signal post-processing method is compared. The comparison results show that the method of removing incomplete reception regions directly is better.

Linearized Euler Solver for Rapid Frequency-Domain Aeroelastic Analysis

2012 ◽  
Vol 49 (3) ◽  
pp. 922-932 ◽  
Author(s):  
Z. Zhang ◽  
S. Yang ◽  
P. C. Chen
Keyword(s):  
Frequency Domain ◽  
Aeroelastic Analysis ◽  
Euler Solver

Computation of internal aerodynamic noise from a quick-opening throttle valve using frequency-domain acoustic analogy

2005 ◽  
Vol 66 (11) ◽  
pp. 1278-1308 ◽  
Author(s):  
Jewook Ryu ◽  
Cheolung Cheong ◽  
Sungtae Kim ◽  
Soogab Lee
Keyword(s):  
Frequency Domain ◽  
Aerodynamic Noise ◽  
Acoustic Analogy ◽  
Throttle Valve

A Simulation Model of a Hydraulic Buck Converter Based on a Mixed Time Frequency Domain Iteration

2013 ◽  
Author(s):  
Helmut Kogler ◽  
Rudolf Scheidl ◽  
Michael Ehrentraut
Keyword(s):  
Wave Propagation ◽  
Frequency Domain ◽  
Buck Converter ◽  
Switching Converters ◽  
Hydraulic Systems ◽  
Pipe System ◽  
Time Frequency ◽  
Crucial Component ◽  
Propagation Effects ◽  
Pressure Changes

Digital hydraulics is an opportunity to realize simple, robust, cheap and energy efficient hydraulic drives. In such systems digital on/off valves are used instead of proportional valves. Moreover, in hydraulic switching converters the valves are actuated within a few milliseconds, which create sharp pressure changes and, in turn, significant wave propagation effects in the pipe system. For a proper design of digital hydraulic systems a sound understanding of these effects is required to achieve the desired behavior of the switching drive system. In such converters, like the buck-, boost or boost-buck-converter, the inductance is one crucial component. It is realized by a simple pipe mainly for cost reasons. Furthermore, switching converters contain some components with nonlinear characteristics, like valves or accumulators, which prevent a comprehensive analysis in frequency domain. For a convenient analysis a qualified model of a hydraulic buck converter based on a mixed time frequency domain iteration is presented. Main parameters of this model are identified and wave propagation effects in the inductance pipe of the converter are investigated by simulation.

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