Quantum and acoustic scattering on R+ and a representation of the scattering matrix

2017 ◽  
Author(s):  
Alexander S. Mikhaylov ◽  
Victor S. Mikhaylov
Keyword(s):  
Acoustic Scattering ◽  
Scattering Matrix

scholarly journals Direct Assessment of the Acoustic Scattering Matrix of a Turbulent Swirl Combustor by Combining System Identification, Large Eddy Simulation and Analytical Approaches

2018 ◽  
Vol 141 (2) ◽  
Author(s):  
Malte Merk ◽  
Camilo Silva ◽  
Wolfgang Polifke ◽  
Renaud Gaudron ◽  
Marco Gatti ◽  
...  
Keyword(s):  
System Identification ◽  
Large Eddy Simulation ◽  
Transfer Matrix ◽  
Acoustic Scattering ◽  
Scattering Matrix ◽  
Series Data ◽  
Swirl Combustor ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Analytical Approaches

This study assesses and compares two alternative approaches to determine the acoustic scattering matrix of a premixed turbulent swirl combustor: (1) The acoustic scattering matrix coefficients are obtained directly from a compressible large eddy simulation (LES). Specifically, the incoming and outgoing characteristic waves f and g extracted from the LES are used to determine the respective transmission and reflection coefficients via System Identification (SI) techniques. (2) The flame transfer function (FTF) is identified from LES time series data of upstream velocity and heat release rate. The transfer matrix of the reactive combustor is then derived by combining the FTF with the Rankine–Hugoniot (RH) relations across a compact heat source and a transfer matrix of the cold combustor, which is deduced from a linear network model. Linear algebraic transformation of the transfer matrix consequently yields the combustor scattering matrix. In a cross-comparison study that includes comprehensive experimental data, it is shown that both approaches successfully predict the scattering matrix of the reactive turbulent swirl combustor.

Estimation of the Acoustic Scattering Matrix for a Centrifugal Pump

2002 ◽  
Author(s):  
M. J. R. Bardeleben ◽  
D. S. Weaver
Keyword(s):  
Centrifugal Pump ◽  
Acoustic Scattering ◽  
Past Research ◽  
Scattering Matrix ◽  
Transmission Matrix ◽  
Inertial Effects ◽  
Simple Modification ◽  
Pump Housing ◽  
New Form ◽  
Predicted Values

This paper presents the results of a theoretical and experimental investigation into the acoustic scattering matrix for a centrifugal pump. Background is provided which examines past research into acoustic two-port models, illustrating the benefits and laying the groundwork for the current incarnation of the scattering matrix. The results reveal that the traditional form of the transmission matrix is not adequate for predicting the parameters of the scattering matrix and a new form is suggested. With a simple modification, the predicted values successfully capture the trend in the experimental data. The presented research is still ongoing, looking to improve the model by including the compliance of the pump housing and inertial effects at the pump ports.

Determination of Acoustic Scattering Matrices from Linearized Compressible Flow Equations with Application to Thermoacoustic Stability Analysis

2019 ◽  
Vol 27 (03) ◽  
pp. 1850027 ◽  
Author(s):  
Max Meindl ◽  
Malte Merk ◽  
Fabian Fritz ◽  
Wolfgang Polifke
Keyword(s):  
Stability Analysis ◽  
Compressible Flow ◽  
Stokes Equations ◽  
Acoustic Scattering ◽  
Scattering Matrix ◽  
Major Influence ◽  
Test Rig ◽  
Viscous Effects ◽  
Flow Equations ◽  
Scattering Matrices

The acoustic transmissions and reflections of plane waves at duct singularities can be represented with so-called scattering matrices. This paper shows how to extract scattering matrices utilizing linearized compressible flow equations and provides a comparative study of different governing equations, namely the Helmholtz, linearized Euler and linearized Navier–Stokes equations. A discontinuous Galerkin finite element method together with a two-source forcing is employed. With this method, the scattering matrix for a radial swirler of a combustion test-rig is computed and validated against the results of a fully compressible Large-Eddy-Simulation. Analogously, the scattering behavior of an axial swirler is investigated. The influence of acoustic-hydrodynamic interactions, viscous effects as well as unsteady boundary layers on the results is investigated for both configurations. A thermoacoustic stability analysis of the combustion test-rig housing the axial swirler is carried out, utilizing the scattering matrix of the swirler. Major influence of the reflections coming from the swirler on the thermoacoustic eigenfrequencies is found.

scholarly journals Experimental Investigation on the Acoustic Scattering Matrix for a Centrifugal Pump

Proceedings ◽  
2018 ◽  
Vol 2 (23) ◽  
pp. 1489
Author(s):  
Guidong Li ◽  
Jorge Parrondo ◽  
Yang Wang
Keyword(s):  
Centrifugal Pump ◽  
Sound Source ◽  
Acoustic Pressure ◽  
Fluid Dynamic ◽  
Acoustic Scattering ◽  
Scattering Matrix ◽  
Acoustic Properties ◽  
Pressure Waves ◽  
Centrifugal Pumps ◽  
Dynamic Noise

Fluid-dynamic noise in centrifugal pumps as a significant sound source in piping systems has gained high attention due to the requirements of vibration and noise reduction in many fields. The acoustic characteristics of the fluid-dynamic noise from pumps are bound to be affected by the pipe ports and other piping components during the operation of the pump system. Therefore, the direct measurement of pressure pulsations in the pipeline of a test pump does not directly reflect the acoustic properties of the pump itself, because the coupling effects of the hydraulic system, which can even cause standing waves, may be seriously misleading in some situations. In this paper, an alternative experimental method has been applied to identify the so-called acoustic scattering matrix of a laboratory centrifugal pump. The elements of the scattering matrix characterize how the acoustic pressure waves are transmitted or reflected from the pump ports, i.e., it summarizes the passive acoustic properties of the pumps. For the tests, the test pump was connected in parallel to another auxiliary pump driven with a variable-frequency that played the role of an external sound source. The acoustic pressure waves induced in the suction and discharge pipes were mathematically decomposed into the corresponding incoming and exiting pressure waves travelling in the positive (P+) and negative (P−) directions respectively, by means of the two-microphone procedure. This paper shows the elements of the scattering matrix determined for the test pump as a function of frequency. These results represent a reference for subsequent theoretical research on the acoustic scattering matrix of centrifugal pumps.

scholarly journals Direct Assessment of the Acoustic Scattering Matrix of a Turbulent Swirl Combustor by Combining System Identification, Large Eddy Simulation and Analytical Approaches

2018 ◽  
Author(s):  
Malte Merk ◽  
Camilo Silva ◽  
Wolfgang Polifke ◽  
Renaud Gaudron ◽  
Marco Gatti ◽  
...  
Keyword(s):  
System Identification ◽  
Large Eddy Simulation ◽  
Transfer Matrix ◽  
Acoustic Scattering ◽  
Scattering Matrix ◽  
Series Data ◽  
Swirl Combustor ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Analytical Approaches

This study assesses and compares two alternative approaches to determine the acoustic scattering matrix of a pre-mixed turbulent swirl combustor: 1) The acoustic scattering matrix coefficients are obtained directly from a compressible Large Eddy Simulation (LES). Specifically, the incoming and outgoing characteristic waves f and g extracted from the LES are used to determine the respective transmission and reflection coefficients via System Identification techniques. 2) The flame transfer function (FTF) is identified from LES time series data of upstream velocity and heat release rate. The transfer matrix of the reactive combustor is then derived by combining the FTF with the Rankine-Hugoniot relations across a compact heat source and a transfer matrix of the cold combustor, which is deduced from a linear network model. Linear algebraic transformation of the transfer matrix consequently yields the combustor scattering matrix. A cross-comparison study that includes comprehensive experimental data shows that both approaches successfully predict the scattering matrix of the reactive turbulent swirl combustor.

“Preparation of Single Crystalline Gold Films for ED Studies”

1972 ◽  
Vol 30 ◽  
pp. 634-635
Author(s):  
Joseph D. C. Peng
Keyword(s):  
Crystal Morphology ◽  
Diffraction Theory ◽  
Scattering Matrix ◽  
Vacuum Evaporation ◽  
Gold Films ◽  
Matrix Formulation ◽  
Silver Films ◽  
Single Crystalline ◽  
Grating Pattern ◽  
Stacking Disorder

The relative intensities of the ED spots in a cross-grating pattern can be calculated using N-beam electron diffraction theory. The scattering matrix formulation of N-beam ED theory has been previously applied to imperfect microcrystals of gold containing stacking disorder (coherent twinning) in the (111) crystal plane. In the present experiment an effort has been made to grow single-crystalline, defect-free (111) gold films of a uniform and accurately know thickness using vacuum evaporation techniques. These represent stringent conditions to be met experimentally; however, if a meaningful comparison is to be made between theory and experiment, these factors must be carefully controlled. It is well-known that crystal morphology, perfection, and orientation each have pronounced effects on relative intensities in single crystals.The double evaporation method first suggested by Pashley was employed with some modifications. Oriented silver films of a thickness of about 1500Å were first grown by vacuum evaporation on freshly cleaved mica, with the substrate temperature at 285° C during evaporation with the deposition rate at 500-800Å/sec.

Reduction of the scattering matrix array

2015 ◽  
Vol 185 (9) ◽  
pp. 941-945 ◽  
Author(s):  
Ivan A. Sadovskyy
Keyword(s):  
Scattering Matrix ◽  
Matrix Array
Sign in / Sign up

Export Citation Format

Share Document