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Computational aeroacoustics deals with the computation of noise generated arodynamically. In order to solve this problem, and given the difference between flow and acoustic scales, the direct computation of aeroacoustic noise by solving the compressible unsteady Navier-Stokes equations for the whole domain of interest, becomes prohibitively expensive for most of industrial applications. In order to overcome the computational burden while preserving an engineering accuracy level, hybrid methods emerge, where the noise source generation and the noise propagation are computed separately. In these hybrid methodologies, aeroacoustic sources are first identified by solving the compressible avier-Stokes equations in a reduced domain. Then, these sources are introduced in a set of suitable propagation equations like the Linearized Euler Equations or the Acoustic Perturbation Equations. The cost of solving these propagation equations is much lower than it would be if the Navier-Stokes equations have to be solved all the way to the far field. The quality of the aeroacoustic sources identified in the first step is of paramount importance in order to obtain accurate results for the sound pressure level in the medium-far field. When solving the Navier-Stokes equations in order to identify these sources, turbulence can be approached in different ways. In Large Eddy Simulation, the Navier-Stokes equations are filtered, and only the big, energy containing eddies are resolved, whereas the small scales of turbulence and its influence in the resolved scales has to be modeled with a subgrid scale model. This approach is different from Direct Numerical Simulation, where all the turbulent scales are resolved. The grid size and the computational power needed for a Large Eddy Simulation is orders of magnitude smaller than what is needed for a Direct Numerical Simulation, making the first approach, again, much more attractive for industrial applications. The purpose of this research is to develop numerical techniques that allow for an accurate computation of noise sources using Large Eddy Simulation, as well as to make an assessment of the real capabilities of hybrid methodologies for subsonic flows. Door de almaar strenger wordende geluidsreglementeringen, wordt er steeds meer aandacht besteed aan het onderzoek naar de vermindering van geluid. Één van de bronnen van geluidoverlast is het zogenaamde stromingsgeluid (aëro-akoestiek) dat veroorzaakt wordt door de aanwezigheid van een turbulente stroming, een aerodynamische opwekking. Voorbeelden van gunstige vormen van strominggeluid zijn terug te vinden bij muziekinstrumenten zoals de trompet, het orgel en de saxofoon. Het overgrote deel van dit aerodynamisch opgewekt geluid wordt echter als nadelig ervaren. Denken we maar aan het landingsgeluid van vliegtuigen, het geluid in een auto door een open (dak)raam of het geluid van de kleine ventilatoren die veelvuldig geïnstalleerd worden in ijskasten en computers. Tegenwoordig zijn er vaak uitgebreide, dure en tijdsintensieve meetcampagnes op verschillende prototypes nodig voor het ‘stromingsgeluidarme’ ontwerp van deze verschillende componenten. Vandaar, dat dit onderzoek zich richt op de ontwikkeling van numerieke tools om dit stromingsgeluid te voorspellen. Dit laat toe om al in een pril ontwerpstadium bepaalde wijzigingen aan te brengen en kan op langere termijn de prototypetesten vervangen. Als toepassingsdomein bestudeert dit onderzoek voornamelijk subsone en gedwongen stromingen, die voorkomen in uitlaatdempers van auto’s, HVAC installaties en andere leidingsystemen. Due to the ever more restrictive legal regulations regarding noise emissions and human response to noise in domestic areas and in working and living environments as well as the growing customer demand for noise comfort, the research in the field of acoustics has grown significantly during the past decades. One of the sources of noise nuisance is flow noise (aeroacoustics) which is cause by the presence of a turbulent flow field. Examples of beneficial flow noise are encountered in musical instruments such as a trumpet, an organ and a saxophone. The major part of this aerodynamically generated noise is however perceived as a form of nuisance. The landing noise of airplanes, de noise generated by opening the sunroof or side window of a car or the noise caused by the small fans that are commonly installed in refrigerators and computers are all examples of this kind of aerodynamic noise. At present, expensive and time-consuming experimental campaigns are required to reduce the flow noise emission from these different components. For this reason, this Ph.D. research focuses on the development of numerical prediction tools to simulate this aerodynamically generated noise. This allows make certain modifications already at the start of the design. As major application this research studies confined, subsonic flows, which are encountered in automotive muffler applications, HVAC installations and other duct systems.

Academic collection --- 534.1 <043> --- Vibration of bodies. Excitation of vibrations. Vibratory formations with distributed mass and elasticity--Dissertaties --- Theses --- 534.1 <043> Vibration of bodies. Excitation of vibrations. Vibratory formations with distributed mass and elasticity--Dissertaties

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534.1 --- Vibration --- Cycles --- Mechanics --- Sound --- Vibration of bodies. Excitation of vibrations. Vibratory formations with distributed mass and elasticity --- 534.1 Vibration of bodies. Excitation of vibrations. Vibratory formations with distributed mass and elasticity --- Vibrations

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Vibration --- mechanische trilling --- 534.1 --- 534.1 Vibration of bodies. Excitation of vibrations. Vibratory formations with distributed mass and elasticity --- Vibration of bodies. Excitation of vibrations. Vibratory formations with distributed mass and elasticity --- Cycles --- Mechanics --- Sound --- Problems, exercises, etc

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This volume contains a timely collection of research papers on the latest developments in the ever-increasing use of elastic waves in a variety of contexts. There are reports on wave-propagation in various types of media: in both isotropic and anisotropic bodies; in homogeneous and inhomogeneous media; in media with cracks or inclusions in random media; and in layered composites.The bulk of the papers are concerned with propagation in elastic media, but also included are viscoelastic, thermoelastic and magneto-electroelastic wave propagation, as well as waves in porous and piezo-electric bodie

534.1 --- Elastic waves --- -Wave-motion, Theory of --- -Undulatory theory --- Mechanics --- Elasticity --- Waves --- Underground nuclear explosions --- Vibration of bodies. Excitation of vibrations. Vibratory formations with distributed mass and elasticity --- Congresses --- Elastic wave propagation --- Wave-motion, Theory of --- -Vibration of bodies. Excitation of vibrations. Vibratory formations with distributed mass and elasticity --- 534.1 Vibration of bodies. Excitation of vibrations. Vibratory formations with distributed mass and elasticity --- -534.1 Vibration of bodies. Excitation of vibrations. Vibratory formations with distributed mass and elasticity --- Undulatory theory --- Propagation of elastic waves --- Propagation

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Proefschriften --- Thèses --- 534.1 <043> --- Academic collection --- #TWER:DISS --- Vibration of bodies. Excitation of vibrations. Vibratory formations with distributed mass and elasticity--Dissertaties --- Theses --- 534.1 <043> Vibration of bodies. Excitation of vibrations. Vibratory formations with distributed mass and elasticity--Dissertaties