Sökning: "Duct Modes"

Visar resultat 1 - 5 av 11 avhandlingar innehållade orden Duct Modes.

  1. 1. Integrated Duct Aerodynamics

    Författare :Elias Siggeirsson; Chalmers tekniska högskola; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; DDES; RANS; CFD; Compressor duct; Spalart-Allmaras;

    Sammanfattning : Air traffic is rapidly increasing, with no sign of slowing down, resulting in increased green-house gases emission. With emission criteria becoming stricter every year, the aircraft design is subjected to continuous improvements. The development of more efficient aircraft engines plays a central role in the strive towards lower emission levels. LÄS MER

  3. 2. Numerical Methods for Aeroacoustic Analysis of Turbomachines

    Författare :Daniel Lindblad; Chalmers tekniska högskola; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; NATURVETENSKAP; NATURAL SCIENCES; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Stability Analysis; Acoustic Analogy; Tonal Noise; Nonreflecting Boundary Conditions; Duct Modes; Turbomachinery; Harmonic Balance; Ffowcs Williams - Hawkings; Time Sampling; Aliasing;

    Sammanfattning : Numerical simulations are important tools for developing new aircraft that can meet future needs. When numerical simulations are used to compute aircraft noise, a two-step procedure is often employed. In the first step, the noise sources are determined using, e.g. LÄS MER

  4. 3. 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

  5. 4. Spectral-element simulations of turbulent wall-bounded flows including transition and separation

    Författare :Johan Malm; Dan Henningson; Philipp Schlatter; Suad Jakirlic; KTH; []
    Nyckelord :spectral-element method; direct numerical simulation DNS ; large-eddy simulation LES ; turbulence; transition; over-integration; three-dimensional separation; massively parallel simulations; proper orthogonal decomposition POD ; Koopman modes; vorticity stretching; coherence; SRA - E-vetenskap SeRC ; SRA - E-Science SeRC ;

    Sammanfattning : The spectral-element method (SEM) is used to study wall-bounded turbulent flowsin moderately complex geometries. The first part of the thesis is devoted to simulations of canonical flow cases, such as temporal K-type transitionand turbulent channel flow, to investigate general resolution requirements and computational efficiency of the numerical code nek5000. LÄS MER

  7. 5. Acoustic scattering in ducts and influence of flow coupling

    Författare :Susann Boij; KTH; []
    Nyckelord :sound; vortex sheet; flow separation; end correction; Strouhal number; non-orthogonal modes; energy balance; TECHNOLOGY; TEKNIKVETENSKAP;

    Sammanfattning : The subject of this thesis is the acoustic properties offlow duct area expansions and the influence of flow-acousticcoupling at sharp edges. For low Mach number flow, significantinteraction between the sound field and the flow field canoccur at such points of flow separation. LÄS MER