My SPIP site

Leandro Dantas de Santana

csg — 2010-08-01T11:19:50Z

Background:
Master on Aeronautical Engineering - São Paulo University - Brazil.

PhD Project:
Development of high accuracy hard/soft wall transition model for impedance eduction on grazing flows.

High performance acoustic absorbent materials are preferred on applications like turbofan airplanes engines, automotive exhaust systems, etc. In order to characterize the attenuation properties on a non-quiescent medium accurate measurement techniques are required. Indirect measurements techniques are preferred over direct ones due its lower costs involved and reduced time-consumption. On the present work a low frequency indirect impedance measurement technique is adopted, based on a passive two port formulation also known as a linear acoustic network model. This technique deduces the impedance on grazing flows with a good accuracy, but in order to improve the precision of this formulation it is necessary to take on account the noise scattering present on the hard/soft wall transition to precisely deduces the impedance of the acoustic absorbent material. The present project intends to develop a hard/soft wall transition analytical model and validate it using FEM and experimental data.

Lectures and Workshops attended:
- Aether Meeting and Workshop: "Perspectives for the Use of Bio-Fuels in Combustion Systems" / Piteå and Luleå (Sweden) / 14th -17th March 2010
- Summer School and Workshop on Non-normal and non-linear effects in Aero- and Thermoacoustics / Munich (Germany) / 17th - 20th May 2010
- 16th AIAA/CEAS Aeroacoustics Workshop / Stockholm (Sweden) / 7th to 9th June 2010

Projected date of Defense:
December 2013

Korcan Kucukcoskun

csg — 2010-02-15T17:17:17Z

Background:
M.Sc. In Aeronautics and Astronautics from Istanbul Technical University, Turkey.

Project:

The objective of the thesis is modelisation of the broadband noise emitted by industrial fans and computation of the broadband noise scattering.
One of the major contributors of the broadband noise source for low speed industrial fans is the incoming turbulence noise. The theory proposed by Amiet is used in order to predict the acoustic field of an airfoil located in a turbulent stream. As a first step, the tests are performed for a stationary airfoil located in the transition zone of a jet flow. The current theory is extended to predict the sound level in the geometrical near-field of the airfoil. A segmentation method is applied to take the spanwise varying flow conditions into account. And the scattered-field of the noise emitted by the airfoil is computed using a flat screen. Both free- and scattered-field computations are validated by the measurements performed in an anechoic chamber. The next step will be taking the effects of rotation into account.

Publications:
- Kucukcoskun K., Christophe J., Schram C., Anthoine J., Tournour M., An Extension of Amiet's Theory for Spanwise-Varying Incident Turbulence and Broadband Noise Scattering Using a Boundary Element Method, 16th AIAA/CEAS Aeroacoustics Conference, 7th-9th June 2010, Stockholm
- Kucukcoskun K., Christophe J., Schram C., Anthoine J., Tournour M., A Geometrical Near-Field Extension of Amiet's Theory for Spanwise Varying Incoming Turbulence Noise and Broadband Noise Scattering, ISMA Conference, 20th-22nd September 2010, Leuven (Abstract accepted)

Tanya Stanko

csg — 2010-02-15T09:53:19Z

Background:
PhD Computational Aeroacoustics, the University of Leeds, UK (2010);
Mc.S. Applied Physics and Mathematics, Moscow Institute of Physics and Technology, Russia

Project:

Acoustic source identification at low Mach numbers in pipe systems. An acoustic resonance in a pipe system is generally negative effect since it leads to a rapid distraction of the system. Typically this effect occurs when characteristic length of the system element is proportional to an integer number of quarters of the acoustical wavelength. The shear layer formed in the pipe system element (T-joint, orifice, flow expansion) can either absorb or generate sound thus preventing a resonance to occur or, on the contrary, contributing to its development. A methodology combining CFD flow simulations, vortex sound theory, and system identification techniques is to be developed for identification of the acoustical response of the pipe system.

6th Meeting: Cambridge, September 2009

csg — 2009-10-05T06:16:58Z

Fellows Presentations

Anna Müller - Numerical investigation of aerodynamic noise generation in confined flows.

Burak Göktepe - Thermo-acoustic instabilities within Biomass Combustion.

Devis Tonon - Multiple side-branch system as a model for corrugated pipes.

Evgeniy Volkov - Influence of electric field on flames: Thermoacoustic applications.

Geraud Gouilloud - Deterministic / stochastic method for aeroacoustic sound prediction applied to diaphragm flow.

Gary Jasor - Large Eddy Simulations of flow at aera expansion.

Balachandran Karthik - 1D network modelling of simplified combustion system.

Kerstin Wieczorek - LES on Acoustic Damping in Cavities.

Lilla Koloszar - Numerical prediction of noise propagation with hybrid method.

Manohar - Instability prediction of a condensing boiler: an experimental study.

Owen Graham - Modelling a Simple Lean Premixed Flame.

Paula Martinez-Lera - Numerical prediction of sound in confined flows: implementation of source effects through boundary conditions.

Robert Leandro - Low-order Model and Stability Analysis of non-compact Flames.

Umesh Bhayaraju - Effect of Cooling liners on the Combustion Instabilities in an Atmospheric Combustor..

Gary Jasor

csg — 2009-10-02T16:05:10Z

PhD Student at TU Munich, Germany

Background:
Engineer in Applied Mathematics and Scientific Calculation. Sup' Galilée engineering school (Villetaneuse, FRANCE)

PhD Project:

Lectures and Workshops attended:
- AETHER Workshop on thermoacoustics and control, 09.-10. 09. 2009, UCAM, Cambridge

Projected date of Defense:
December 2012

Publications:

Coverage on AETHER in eStrategies

csg — 2009-09-04T09:40:32Z

The eStrategies magazines of British Publisher's "...track the business opportunities arising from transition in Europe, Africa and the Middle East."

Recently, this magazine published a coverage on the project AETHER, reporting both on the technical background of the research project as on training aspects and the socio-economic impact:

"With emission regulations set to grow more stringent, improving energy efficiency is real priority for combustor manufacturers; yet stability must not be compromised. Dr Christophe Schram, coordinator of AETHER, explains how research into aero-acoustic and thermo-acoustic coupling addresses this."

Feature in eStrategies on the project AETHER.

"Combining technical expertise with commercial knowledge can lead to the development of practically-focused research, says Dr Karthik Balachandran, who expands on the AETHER project's work in developing numerical, experimental and modelling techniques, research designed to address thermo-acoustic issues."

Interview with Dr. Karthik Balachandran.

Anna Müller

csg — 2009-09-04T08:52:12Z

PhD Student at VKI, Brussels (Belgium)

Background:
Msc. Eng. Computational Mechanics in Environmental Engineering, Cracov University of Technology, Cracov, Poland.

PhD Project:

NUMERICAL INVESTIGATION OF AERODYNAMIC NOISE IN CONFINED FLOWS
Noise can be generated by structural vibrations, flow field, thermal processes. This project focuses on noise generation in industrial piping, due to turbulent flow, obstruction, bends. There exist many numerical approaches to solve the problem of sound generated and propagated in a flow field (Computational AeroAcoustics) . We concentrate on using so called hybrid methods. First one solves the dynamics of the flow (Large Eddy Simulation). The data obtained from a transient calculation is used to define the sound source using the aeroacoustic analogy (Lighthill, Curle, Ffowks Williams-Hawkings...) The sound is then propagated in a separate simulation/code.

By studying the academic problems we attempt to define a procedure for acoustic computation in industry using/modifying commercial codes. The influence of different inflow/outflow boundary conditions, mesh resolution, the flow solution accuracy, and the analogies used on the acoustic field are studied.

Sound generated by vortex shedding behind a confined square cylinder is being solved. The flow regime is turbulent. The flow field is obtained by incompressible LES in Fluent and results exported for further calculation in SYSNOISE.

Lectures and Workshops attended:
- Seminar on 'Introduction to Numerical Aeroacoustics', 23.02.2007, VKI, Brussels
- Workshop on “Aeroacoustics” during the EUCASS Conference, 01.07.2007, ULB
- AETHER Course: Introduction to Acoustics and Combustion, 01.-05. 10. 2007, TU/e, Eindhoven
- AETHER Course: Basics of Aero- and Thermoacoustics, 03.–07. 12. 2007, VKI, Brussels
- LMS Virtual.Lab training, 25-29. 02. 2008, Leuven
- AETHER Workshop on acoustic network code TaX, 07.-09. 04. 2008, TUM, Munich
- Lecture Series: “Aerodynamic noise from wall-bounded flows”, 9.-13. 03. 2009, VKI, Brussels, Belgium

Projected date of Defense:
December 2010

Publications:
- A. Mueller, P. Rambaud, J. Anthoine “Vortex Shedding in a Confined Laminar Flow Past a Square Cylinder” ECCOMAS 2008, Venice, July 2008
- A. Mueller, P. Martinez, P. Rambaud, J. Anthoine, Ch. Schram “Robust aeroacoustic computations based on Curle's analogy and Vortex Sound Theory for a confined flow case”, ISMA 2008, Leuven, September 2008

Evgeniy Nikolaevich Volkov

csg — 2009-07-20T18:19:20Z

Post-doctoral fellow at TU/e, Eindhoven (Netherlands)

Background:
Candidate of Physico-Mathematical Sciences (equivalent of PhD), Chemical Physics, including Physics of Combustion and Explosion, Novosibirsk State University

AETHER fellow 01.07.2008 - 30.11.2010.

Project:
Influence of electric field on the thermoacoustic behaviour of laminar flames.
Reduction of combustion noise and suppression of combustion instabilities is of significant importance for many industrial and domestic burning devices. The problem of acoustic instability significantly increases the cost and time needed to design and refine new heating equipment. Measures to eliminate the instability can be applied either via modifying the acoustic properties of the combustor vessel or via modifying the thermo-acoustic properties of the flame/burner.
These modifications can be applied either in a passive or in an active manner. The passive measures can be divided into two groups: 1) augmentation of the damping of acoustic energy in the system; 2) shift of the phasing between pressure and heat release oscillations in the flame/burner aiming to minimize the Rayleigh integral (energy flow from combustion to acoustic mode). One of the drawbacks of passive control strategies is that the configuration suitable for one set of operation parameters can be unsuitable for other regimes of combustor operation.
This fact stimulates the search of methods to realize so-called adaptive control, when acoustic properties of the system can be altered depending on the operation regime. To realize this strategy, effective, reliable, simple in realization and cheap methods to control the combustor thermo-acoustics are required. One of the promising actuators for active control of combustion instabilities is an electric field (EF). The use of EF as a possible actuator is attractive, because it can provide a uniform and spatially distributed influence on the flame. Furthermore, the equipment for the EF generation and manipulation can be made small, cheap, reliable in service and easy to control.
The aim of the project is to study the mechanism of influence of EF on premixed laminar methane/air flames and to improve our understanding of this complex phenomenon. Main emphasis is placed on assessment of the applicability of electric fields for damping thermoacoustic instabilities in the case of burner stabilized, laminar flames. Influence of a DC EF on the thermoacoustic behaviour of flames is characterized through a change in thermoacoustic transfer function (TF). It was already shown that application of a DC EF leads to noticeable changes in thermoacoustic TF of flat flames. It means that in the case of flat premixed methane/air flames a DC EF can be used as an actuator for active control of thermoacoustic oscillations. The aim of future work is to study influence of EF on thermoacoustic behaviour of other types of laminar flames.

Lectures and Workshops attended:
- AETHER Workshop on combustion diagnostics, 20.-24. 04 2009, IST, Lisbon
- AETHER workshop on Thermoacoustics, University of Cambridge, the United Kingdom, 7-10 September, 2009
- Workshop on Combustion Noise, École Centrale Paris, France, November 12, 2009

Publications:
- E.N. Volkov, A.V. Sepman, V.N. Kornilov, A.A. Konnov, Y.S. Shoshin, L.P.H. de Goey, Towards the mechanism of DC electric field effect on flat premixed flames, Proceedings of 4th European Combustion Meeeting, Vienna, 14-17 April, 2009, Austria, Article P810337, pp. 1-6.
- E.N. Volkov et al: Influence of electric field on thermoacoustic transfer function of flat premixed flame, Congress on Sound and Vibration, Krakow, July 5th -9th, 2009, Poland.
- E.N. Volkov et al: Influence of DC electric field on thermoacoustic transfer function of multiple Bunsen-type flames, 17th International Congress on Sound and Vibration, Cairo, July 18th -22nd, 2010, Egypt.

Janaína Gomes de Merícia

csg — 2009-07-20T18:13:37Z

PhD Student at IST, Lisbon (Portugal)

Background:
Master's degree.

PhD Project:
Characterization of nonlinear effects in unsteady impinging flames - Mathematical and experimental modeling The aim of this thesis is to study the self-excited combustion instabilities that occurs in impinging flames, a configuration that can be found in a variety of practical applications (e.g. domestic burners, metal thermal treatment, etc), and it is known to limit seriously the burning under lean conditions (pollutant emission reduction), or the use of alternative fuels or the miniaturization of the burner system towards a more controllable distributed systems. The work envisages the development of a mathematical model to predict the frequency and onset of oscillations followed by experimental research for further validation purposes. The model will allow a physical understanding of the process and may be used to support burner's project that can damp self-excited oscillations.

Lectures and Workshops attended:
- AETHER Workshop on combustion diagnostics, 20.-24. 04 2009, IST, Lisbon

Projected date of Defense:
April 2012

Secondments and Short Visits:
- Technische Universteit Eindhoven, 2 weeks.

Karthik Balachandran

csg — 2009-07-20T18:00:19Z

Post-doctoral fellow at LMS, Leuven (Belgium)

Background:
Doctor of Philosophy, Indian Institute of Technology Madras, India

Project:
Development and application of 1-Dimensional and 3-Dimensional Frequency Domain based Thermo-acoustic computations.

The main objective of my work is the development of computational tools for performing thermo-acoustic analysis of Gas-turbine combustors, Domestic heating systems and Cowper stoves. The work is confined to the use and application of frequency domain methods in both one and three dimensions. The one-dimensional method has certain advantages in terms of speed and ease of setting up the problem but suffers from serious drawbacks when dealing with highly 3-dimensional geometric systems. The three-dimensional methods will be time consuming and expensive in terms of the necessary resources however is expected to be more accurate. The user input to represent the flame -acoustic coupling will be in the form of Flame Transfer function. The developed 1-dimensional tool has been tested by using the Flame transfer function measured by our partners at TU Eindhoven for domestic heating systems and has been found to be quite successful at determining the thermo-acoustic behavior of a laboratory based experimental setup.

Lectures and Workshops attended:
- LMS VL.Acoustics training course, LMS International, 8.-10.09. 2008
- ISAAC20 Seminar on Advanced Techniques in Applied and Numerical Acoustics, KU Leuven, 18.-19.09. 2008
- Professional Presentations, Antoine Vermeire, Com&Co bvba , 4th and 18th February 2009, LMS International, Leuven
- Lecture Series: “Aerodynamic noise from wall-bounded flows”, 9.-13. 03. 2009, VKI, Brussels, Belgium
- AETHER Workshop on combustion diagnostics, 20.-24. 04 2009, IST, Lisbon
- LMS Imagine AMESIM training, LMS International, 18.-19.05. 2009
- Complementary training: “Personal Effectiveness”, Insights, 22nd June 2009, LMS International, Leuven

Publications:
- M. Manohar, B. Karthik, V.N. Kornilov, L. P. H. de Goey: Thermo-acoustic instabilities of simplified boiler: a comparative experimental vs. modeling study. COMBURA 2009, Nieuwegein, The Netherlands
- B. Karthik, H. Beriot and C. Schram, “Rijke tube thermo-acoustic analysis using finite element based Helmholtz solver”, Presented at the 15th AIAA/CEAS Aeroacoustics Conference, Miami, Florida, May 2009.
- Paula Martinez-Lera, S. Foeller, R. Kaess, B. Karthik, Christophe Schram, W. Polifke, Low-Order Modeling of a Side-Branch at Low Mach Numbers, 15th AIAA/CEAS Aeroacoustics Conference, 11st-13th May 2009, Miami, EEUU
- B. Karthik, C. Schram and A Hirschberg, ”Limit Cycle Calculations in a Rijke Tube using One-Dimensional Network Model”, To be presented at the 16th International congress on Sound and Vibration, Krakow, July 2009.