Sökning: "LNSE"

Visar resultat 1 - 5 av 6 avhandlingar innehållade ordet LNSE.

1. 1. Experimental and Numerical Multi-port Eduction for Duct Acoustics

   Författare :Stefan Sack; Abom Mats; Phillip Joseph; KTH; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; acoustics; aeroacoustics; flowacoustics; multi-ports; orifice; silencer; experiment; numeric; IDDES; LNSE; optimization; test rig; Monte Carlo; Teknisk mekanik; Engineering Mechanics;

   Sammanfattning : Sound generation and propagation in circular ducts for frequencies beyond the cut-on frequencies of several higher order acoustic modes is investigated. To achieve this, experimental and numerical set-ups are designed and used to research aeroacoustic interactions between in-duct components and to conceive noise mitigation strategies. LÄS MER

3. 2. Acoustic characterization of orifices and perforated liners with flow and high-level acoustic excitation

   Författare :Lin Zhou; Hans Bodén; Wim De Roeck; KTH; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Bias Flow; Grazing Flow; Nonlinear Acoustics; Acoustic Impedance; Impedance Eduction; Single Mode Straightforward Method; Uncertainty Analysis; LEE; LNSE; Järnvägsgruppen - Ljud och vibrationer; Järnvägsgruppen - Ljud och vibrationer;

   Sammanfattning : This thesis is motivated by the need for noise control in aircraft engine with orifices and perforated liner. The presence of high-level acoustic excitation, different flow situations either bias flow, grazing flow or any combination in the aircraft engine, makes the acoustic behavior complex due to the interaction between sound and flow over the lined wall. LÄS MER

4. 3. A Linearized Navier-Stokes Equations Methodology for Aeroacoustic and Thermoacoustic Simulations

   Författare :Wei Na; Susann Boij; Gunilla Efraimsson; Niklas Andersson; KTH; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Linearized Navier-Stokes Equations LNSE ; frequency domain; tube row heat exchanger; hybrid liner; thermoacoustic instabilities; entropy waves; Rijke-tube; nozzle; Engineering Mechanics; Teknisk mekanik;

   Sammanfattning : Aeroengine noise is one of the dominating noise sources in today’s aircraft. Reduction of the aeroengine noise is related to multiphysics phenomena, and that is subject to different mechanisms, e.g., the coupling between turbulence, flame and sound waves. LÄS MER

5. 4. Frequency Domain Linearized Navier-Stokes Equations Methodology for Aero-Acoustic and Thermoacoustic Simulations

   Författare :Wei Na; Gunilla Efraimsson; Susann Boij; Martinez Lera Paula; KTH; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Linearized Navier-Stokes Equations; frequency domain; fluid equivalent model; hybrid liner; thermoacoustic instabilities; Rijke-tube; Engineering Mechanics; Teknisk mekanik;

   Sammanfattning : The first part of the thesis focuses on developing a numerical methodology to simulate the acoustic properties of a hybrid liner consisting of a perforated plate, a porous layer and a Helmholtz cavity. Liners are always a standard way to reduce noise in today’s aeroengines, e.g. LÄS MER

7. 5. Thermo-Acoustic Properties in Combustion Chambers

   Författare :Guillaume Jourdain; Chalmers tekniska högskola; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Mode Stability Analysis; Computational Aeroacoustics; Screech mode; Arnoldi s Method; Buzz mode; Afterburner; Gas turbine combustor; Combustion instabilities;

   Sammanfattning : Design and analysis methods for gas turbine combustors or afterburners have to be improved in particular regarding the prediction of combustion instabilites. A methodology, which combines the use of a linearized flow solver and an Arnoldi algorithm performing the eigenmode extraction procedure, resolves eigenmodes which are candidates to these instabilities. LÄS MER