Numerical Investigations of Generation and Propagation of Sound Waves in Low Mach Number Internal Flows
2008 (English)Licentiate thesis, comprehensive summary (Other scientific)
Traﬃc is a major source of environmental noise in modern day society. Subsequently, development of new vehicles are subject to heavy governmental legislations. The major noise sources on common road vehicles are engine noise, transmission noise, tire noise and, at high speeds, wind noise. At low speeds (< 30-50 km/h), intake and exhaust noise are particularly important during acceleration. One way to reduce intake and exhaust noise is to attach muﬄers to the exhaust pipes. However, to develop prototypes of muﬄers for evaluation is a costly and time-consuming process. As a consequence, in recent years so-called virtual prototyping has emerged as an alternative. Current industrial simulation methodologies are often rather simple, either neglecting mean ﬂow or including only one-dimensional mean ﬂows. Also, ﬂow generated noise is rudimentary modeled or not included at all. Hence, improved methods are needed to fully beneﬁt from the possibilities of virtual prototyping.
This thesis is divided in two main parts. The ﬁrst topic is related to the development and evaluation of methods to simulate sound propagation and generation in two-dimensional conﬁned geometries with arbitrary internal mean ﬂows present. The performance of a new DNS code is evaluated for aeroacoustical purposes and a frequency domain linearized Navier-Stokes equations methodology is developed for acoustic wave propagation applications. Both methods are validated on a case of an in-duct oriﬁce plate.
In the second part, a so-called global mode decomposition technique is evaluated for aeroacoustical purposes. The ﬂow ﬁeld is described as a sum of the non-orthogonal solutions to its corresponding eigenvalue problem. This enables the acoustic analysis of source terms from each individual global mode, and thus reveals new insight into the sound generating mechanisms.
Place, publisher, year, edition, pages
Stockholm: KTH , 2008. , vi, 33 p.
Trita-AVE, ISSN 1651-7660 ; 2008:58
Fluid Mechanics and Acoustics
IdentifiersURN: urn:nbn:se:kth:diva-9388OAI: oai:DiVA.org:kth-9388DiVA: diva2:113821
2008-10-21, MWL 74, Teknikringen 8, KTH, Stockholm, 10:00 (English)
Polifke, Wolfgang, Prof.
Efraimsson, Gunilla, Dr.Åbom, Mats, Prof.
QC 201011152008-10-302008-10-292010-11-15Bibliographically approved
List of papers