Search for dissertations about: "acoustic liner"

Showing result 1 - 5 of 9 swedish dissertations containing the words acoustic liner.

2. 1. Analysis of Acoustic Absorption with Extended Liner Reaction and Grazing Flow

   Author : Anna Färm; Mats Åbom; Lars Enghardt; KTH; []
   Keywords : TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Sound absorption; acoustic lining; non-locally reacting; boundary layer; grazing flow; sound field; transfer matrix method;

   Abstract : Acoustic absorbing liners are efficient and commonly used measures to reduce sound levels in many fields of application. The sound reducingperformance of the liners is dependent on the acoustic state, defined by e.g. the flow and sound field interacting with the liner. READ MORE

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

   Author : Lin Zhou; Hans Bodén; Wim De Roeck; KTH; []
   Keywords : 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;

   Abstract : 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. READ MORE

5. 3. Large Eddy Simulation for the Analysis of Jet Noise Suppression Devices

   Author : Markus Olander Burak; Chalmers tekniska högskola; []
   Keywords : TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; LES; Mixer-ejector; Aeroacoustics; CAA; Acoustic liner; Broadband time-domain impedance boundary condition;

   Abstract : Stricter noise regulations for commercial aircraft have increased interest in noise reduction techniques within the aerospace industry. To meet the requirements new noise suppression technologies have to be delveoped and the numerical methods need to be validated and possibly improved for the correct assessment of these new technologies. READ MORE

6. 4. Numerical Simulations of Noise Reduction Devices for Aero Engines

   Author : Haukur Hafsteinsson; Chalmers tekniska högskola; []
   Keywords : TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Acoustic liner; G3D; CAA; CFD; CD-nozzle; LES;

   Abstract : Increasing air traffic and denser population around airports have led to stricterregulations on aircraft noise. The engine is the main source of noise of jet aircraft.Decreasing jet engine noise can in some cases reduce sonic fatigue andthereby increase the engine lifetime. READ MORE

7. 5. Large Eddy Simulation for the Analysis of Supersonic Jet Noise Suppression Devices

   Author : Markus Olander Burak; Chalmers tekniska högskola; []
   Keywords : TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; fluidic injection; mixer-ejector; jet noise; Kirchhoff; forward flight effects; LES; acoustic liner; supersonic turbulent jets; broadband time-domain impedance boundary condition; chevrons; shock-associated noise; CAA; aeroacoustics;

   Abstract : Stricter noise regulations for commercial and military aircraft have increased interest in noise reduction techniques within the aerospace industry. To meet the requirements, new noise suppression technologies have to be developed and numerical methods need to be validated and possibly improved for the correct assessment of these technologies. READ MORE