Search for dissertations about: "Frequency-domain propagation"

Showing result 1 - 5 of 29 swedish dissertations containing the words Frequency-domain propagation.

2. 1. Frequency Domain Linearized Navier-Stokes Equations Methodology for Aero-Acoustic and Thermoacoustic Simulations

   Author : Wei Na; Gunilla Efraimsson; Susann Boij; Martinez Lera Paula; KTH; []
   Keywords : 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;

   Abstract : 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. READ MORE

4. 2. A Wave Expansion Method for Aeroacoustic Propagation

   Author : Johan Hammar; Gunilla Efraimsson; Ciarán J. O'Reilly; Wim De Roeck; KTH; []
   Keywords : TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Sound propagation; Sound generation; Aeroacoustics; Aerodynamics; Computational fluid dynamics; Computational aeroacoustics; Numerical methods; Lighthill; Curle; Ffowcs Williams and Hawkings; Frequency-domain propagation; Wave expansion method.; Vehicle and Maritime Engineering; Farkostteknik;

   Abstract : Although it is possible to directly solve an entire flow-acoustics problem in one computation, this approach remains prohibitively large in terms of the computational resource required for most practical applications. Aeroacoustic problems are therefore usually split into two parts; one consisting of the source computation and one of the source propagation. READ MORE

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

   Author : Wei Na; Susann Boij; Gunilla Efraimsson; Niklas Andersson; KTH; []
   Keywords : 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;

   Abstract : 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. READ MORE

6. 4. Modelling of IC-Engine Intake Noise

   Author : Magnus Knutsson; Mats Åbom; Yves Auregán; KTH; []
   Keywords : TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; IC-engine; intake noise; gas dynamics; linear source data; frequency domain; 2-port; losses; air cleaner unit; filter paper; flow; FEM; BEM; charge air cooler; narrow tube; Acoustics; Akustik;

   Abstract : Shorter product development cycles, densely packed engine compartments and intensified noiselegislation increase the need for accurate predictions of IC-engine air intake noise at earlystages. The urgent focus on the increasing CO2 emissions and the efficiency of IC-engines, aswell as new techniques such as homogeneous charge compression ignition (HCCI) mightworsen the noise situation. READ MORE

7. 5. Viscoelastic Materials : Identification and Experiment Design

   Author : Agnes Rensfelt; Torsten Söderström; Händel Peter; Uppsala universitet; []
   Keywords : TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; viscoelastic materials; complex modulus; system identification; optimal experiment design; distributed parameter systems; frequency domain identification; wave propagation; Automatic control; Reglerteknik; Elektroteknik med inriktning mot reglerteknik; Electrical Engineering with specialization in Automatic Control;

   Abstract : Viscoelastic materials can today be found in a wide range of practical applications. In order to make efficient use of these materials in construction, it is of importance to know how they behave when subjected to dynamic load. READ MORE