Developing Computational Tools for Modern Aeroacoustic Research
(2003) Abstract
 The thesis presents the author s research on numerical methods for Computational Aeroacoustics and the development of computational tools with direct applicability in industry. The designers in the gasturbine industry, require accurate methods for predicting the onset and the frequencies of dangerous (pressure) oscillations, like the ones which typically occur in Lean Premixed Prevaporized (LPP) combustors. These modern gas turbine combustors could suffer significant damages or even total mechanical destruction, within fractions of seconds, due to these instabilities. Thus, one is interested in determining the resonance frequencies and the acoustic modes of complex industrial geometries, like a gas turbine combustor or an ejection... (More)
 The thesis presents the author s research on numerical methods for Computational Aeroacoustics and the development of computational tools with direct applicability in industry. The designers in the gasturbine industry, require accurate methods for predicting the onset and the frequencies of dangerous (pressure) oscillations, like the ones which typically occur in Lean Premixed Prevaporized (LPP) combustors. These modern gas turbine combustors could suffer significant damages or even total mechanical destruction, within fractions of seconds, due to these instabilities. Thus, one is interested in determining the resonance frequencies and the acoustic modes of complex industrial geometries, like a gas turbine combustor or an ejection nozzle, for instance. These resonance frequencies we refer to as the eigenvalues and the corresponding acoustic modes are called the eigenmodes of the acoustic system. The Implicitly Restarted Arnoldi Method (IRAM) is a robust and e cient method for solving numerically large generalized eigenvalue problems, of the form: [A][X]= lambda [B][X],where [A] and [B] are large sparse matrices, [X] is called the eigenvector and lambda is the corresponding eigenvalue. The Arnoldi method e ciently computes only a small set of eigenvalues and the corresponding eigenmodes for these very large systems, which typically occur in industry (for example a combustion chamber). As a first step, using IRAM and assuming that the acoustic system can be described by a simple model based on the wave equation with appropriate boundary conditions, the author developed a fast algorithm called ARNOWAVE, and a computer code called ARNO3D based on this algorithm, which can be used to compute these resonance frequencies and the corresponding modes. This code uses a Galerkin finitevolume discretization on unstructured grids made of tetrahedral cells. In a second step, the author has extended the applicability of the proposed method by using the LinearizedEuler equations instead of the wave equation, to include also the effects of variable (in space) flow conditions on the sound propagation. The new algorithm, called ARNOLEE, is based on a Multidimensional Upwind second order discretization using the Low Diffusion A (LDA) distribution scheme. The eigensolver implementing this algorithm, called ARNEU3D, has been modified to work with complex numbers. The ARNOLEE algorithm is capable of computing not only the resonance frequencies quencies and modes but also the stability of these modes. The results obtained with both codes have been compared and validated on a series of test cases, for which analytical solution exists. These algorithms based on the Arnoldi method prove to be well suited for large acoustic computations. The ARNOWAVE and ARNOLEE algorithms have been used to compute the resonance frequencies and the acoustic modes for several industrial applications. (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/record/21406
 author
 Caraeni, Mirela ^{LU}
 opponent

 Professor Noerkaer Soerensen, Jens, Denmark
 organization
 publishing date
 2003
 type
 Thesis
 publication status
 published
 subject
 keywords
 Thermal engineering, unstructured mesh, termoacoustic, acoustic, cfd, applied thermodynamics, Termisk teknik, termodynamik
 pages
 212 pages
 publisher
 VOK LTH box 118 22100 Lund,
 defense location
 Room M:A, MBuilding, Lund Institute of Technology
 defense date
 20031120 14:15
 external identifiers

 other:ISRN: LUTMDN/TMHP03/1016SE
 ISSN
 02821990
 ISBN
 9162858696
 language
 English
 LU publication?
 yes
 id
 65bfb01ec6a2455b8b8d782414b9cd81 (old id 21406)
 date added to LUP
 20070528 15:04:01
 date last changed
 20160919 08:44:56
@phdthesis{65bfb01ec6a2455b8b8d782414b9cd81, abstract = {The thesis presents the author s research on numerical methods for Computational Aeroacoustics and the development of computational tools with direct applicability in industry. The designers in the gasturbine industry, require accurate methods for predicting the onset and the frequencies of dangerous (pressure) oscillations, like the ones which typically occur in Lean Premixed Prevaporized (LPP) combustors. These modern gas turbine combustors could suffer significant damages or even total mechanical destruction, within fractions of seconds, due to these instabilities. Thus, one is interested in determining the resonance frequencies and the acoustic modes of complex industrial geometries, like a gas turbine combustor or an ejection nozzle, for instance. These resonance frequencies we refer to as the eigenvalues and the corresponding acoustic modes are called the eigenmodes of the acoustic system. The Implicitly Restarted Arnoldi Method (IRAM) is a robust and e cient method for solving numerically large generalized eigenvalue problems, of the form: [A][X]= lambda [B][X],where [A] and [B] are large sparse matrices, [X] is called the eigenvector and lambda is the corresponding eigenvalue. The Arnoldi method e ciently computes only a small set of eigenvalues and the corresponding eigenmodes for these very large systems, which typically occur in industry (for example a combustion chamber). As a first step, using IRAM and assuming that the acoustic system can be described by a simple model based on the wave equation with appropriate boundary conditions, the author developed a fast algorithm called ARNOWAVE, and a computer code called ARNO3D based on this algorithm, which can be used to compute these resonance frequencies and the corresponding modes. This code uses a Galerkin finitevolume discretization on unstructured grids made of tetrahedral cells. In a second step, the author has extended the applicability of the proposed method by using the LinearizedEuler equations instead of the wave equation, to include also the effects of variable (in space) flow conditions on the sound propagation. The new algorithm, called ARNOLEE, is based on a Multidimensional Upwind second order discretization using the Low Diffusion A (LDA) distribution scheme. The eigensolver implementing this algorithm, called ARNEU3D, has been modified to work with complex numbers. The ARNOLEE algorithm is capable of computing not only the resonance frequencies quencies and modes but also the stability of these modes. The results obtained with both codes have been compared and validated on a series of test cases, for which analytical solution exists. These algorithms based on the Arnoldi method prove to be well suited for large acoustic computations. The ARNOWAVE and ARNOLEE algorithms have been used to compute the resonance frequencies and the acoustic modes for several industrial applications.}, author = {Caraeni, Mirela}, isbn = {9162858696}, issn = {02821990}, keyword = {Thermal engineering,unstructured mesh,termoacoustic,acoustic,cfd,applied thermodynamics,Termisk teknik,termodynamik}, language = {eng}, pages = {212}, publisher = {VOK LTH box 118 22100 Lund,}, school = {Lund University}, title = {Developing Computational Tools for Modern Aeroacoustic Research}, year = {2003}, }