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| 2. |
- Duwig, Christophe, et al.
(author)
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Large Eddy Simulation of a turbulent flow past a pair of symmetric backward-facing steps: A sensitivity analysis
- 2007
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In: Collection of Technical Papers - 45th AIAA Aerospace Sciences Meeting. - 9781563478901 ; 16, s. 11096-11114
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Conference paper (peer-reviewed)abstract
- Large Eddy Simulation is used to study the flow behind a pair of symmetric backward facing steps. As reported in the literature, the flow exhibits an asymmetric pattern characterized by the deflection of the jet toward of the walls. The LES results are compared to LDA measurements showing the ability of the present numerical tool to capture the complex features of the flow. Furthermore, a sensitivity study is conducted in order to assess the influence of the grid resolution, inflow boundary, channel width (aspect ratio A h) and step size (h) on the flow field. The flow was found to be weakly sensitive to the grid, assuring the quality of the simulation results. The inflow boundary influences the results only marginally unless low frequency fluctuations are applied. In this case, the flow field recovers symmetry with suppression of the jet bending. The jet bending has also been shown to increase with the step size h and to reduce with increasing Ah.
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| 3. |
- Duwig, Christophe, et al.
(author)
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Numerical study of thermo-acoustic waves generation by a swirling flame using a new approach based on large eddy simulation
- 2005
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In: Proceedings of the ASME Turbo Expo. ; 2, s. 67-75, s. 67-75
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Conference paper (peer-reviewed)abstract
- The new challenge of the Gas Turbine industry is to develop new technologies for meeting electricity demand growth and reducing harmful emissions. Thus, a better understanding of the combustion phenomenon and an improvement in simulation capabilities are needed. In this paper, we present a new technique that is computationally efficient, for capturing the thermo-acoustic waves in low Mach number combustors. The idea is to utilize the fact that the acoustic related pressure fluctuations are small as compared to the dynamic pressure. Semi-compressible LES of reacting flow is performed and while the pressure perturbations related to the acoustic-wave propagation are handled separately. The equations are solved individually while allowing interaction between the two systems. The technique has been applied to the study of the generation and propagation of thermo-acoustic waves in a combustion chamber. A sensitivity analysis is presented and most important instability modes are identified. Copyright
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| 4. |
- Duwig, Christophe, et al.
(author)
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Simulations of a turbulent flow past a sudden expansion : A sensitivity analysis
- 2008
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In: AIAA Journal. - : American Institute of Aeronautics and Astronautics (AIAA). - 0001-1452 .- 1533-385X. ; 46:2, s. 408-419
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Conference paper (peer-reviewed)abstract
- Large eddy simulation is used to study the flow behind a pair of symmetric backward-facing steps. As reported in the literature, the flow exhibits an asymmetric pattern characterized by the deflection of the jet toward one of the walls. The large eddy simulation results are compared with laser Doppler anemometry measurements showing the ability of the present numerical tool to capture the complex features of the flow. Furthermore, a sensitivity study is conducted to assess the influence of the grid resolution, the inflow boundary, the channel width, and the step size on the flowfield. The flow was found to be only weakly sensitive to the grid, assuring the quality of the simulation results. The inflow boundary influences the mean results only marginally unless low-frequency fluctuations are applied. In this case, the flowfield recovers a mean symmetry with suppression of the jet bending. The jet mean bending has also been shown to increase with the step size h and to decrease with increasing channel width.
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| 7. |
- Kusano, Yukihiro, et al.
(author)
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Stability of alternating current gliding arcs
- 2014
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In: European Physical Journal D. Atomic, Molecular, Optical and Plasma Physics. - : Springer Science and Business Media LLC. - 1434-6060. ; 68:10, s. 9-319
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Journal article (other academic/artistic)
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| 8. |
- Kusano, Yukihiro, et al.
(author)
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Water-cooled non-thermal gliding arc for adhesion improvement of glass-fibre-reinforced polyester
- 2013
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In: Journal of Physics D: Applied Physics. - : IOP Publishing. - 1361-6463 .- 0022-3727. ; 46:13
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Journal article (peer-reviewed)abstract
- A non-equilibrium quenched plasma is prepared using a gliding-arc discharge generated between diverging electrodes and extended by a gas flow. It can be operated at atmospheric pressure and applied to plasma surface treatment to improve adhesion properties of material surfaces. In this work, glass-fibre-reinforced polyester plates were treated using an atmospheric pressure gliding-arc discharge with air flow to improve adhesion with a vinylester adhesive. The electrodes were water-cooled so as to operate the gliding arc continually. The treatment improved wettability and increased the density of oxygen-containing polar functional groups on the surfaces. Double cantilever beam specimens were prepared for fracture mechanic characterization of the laminate adhesive interface. It was found that gliding-arc treatment significantly increases the fracture resistance in comparison with a standard peel-ply treatment.
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| 9. |
- Salewski, Mirko, et al.
(author)
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A comparison of a single- and multiphase jets in a crossflow using LES
- 2005
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In: Proceedings of the ASME Turbo Expo. ; 2, s. 77-86
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Conference paper (peer-reviewed)abstract
- Large eddy simulations are performed for a single- and multiphase jets in crossflow (JICF). The multiphase JICF are compared to the single-phase case for the same momentum and mass flow ratios but with droplets of different sizes. Multiphase JICF have stronger counter-rotating vortex pairs (CVPs) than a corresponding single-phase JICF. Moreover, their trajectories are higher and their induced wakes weaker. The smaller the Stokes number of the droplets, the more the solution approaches the solution for single-phase flow. The computed results show the formation of a CVP and horseshoe vortices which are convected downstream. LES reveals also the intermittent formation of upright wake vortices from the horseshoe vortices on the ground towards the CVP. The dispersion of polydisperse spray droplets is computed using the stochastic parcel method. Atomization and droplet breakup are modeled by a combination of the breakup model by Reitz and the Taylor analogy breakup model. Evaporation and droplet collision are also modeled. The flow solver uses two-way coupling. Averages of the velocity and gaseous fuel mass fraction are computed. The single-phase JICF is validated against experimental data obtained by PIV. Additionally, the PDFs and frequency spectra are presented. Copyright
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| 10. |
- Salewski, Mirko, et al.
(author)
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A comparison of single and multiphase jets in a crossflow using large eddy simulations
- 2007
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In: Journal of engineering for gas turbines and power. - : ASME International. - 0742-4795 .- 1528-8919. ; 129:1, s. 61-68
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Journal article (peer-reviewed)abstract
- Large eddy simulations (LES) are performed for single and multiphase jets in crossflow (JICF). The multiphase JICF are compared to the single-phase case for the same momentum and mass flow, ratios but with droplets of different sizes. Multiphase JICF have stronger counterrotating vortex pairs (CVPs) than a corresponding single-phase JICF. Moreover their trajectories are higher and their induced waves weaker. The smaller the Stokes number of the droplets, the more the solution approaches the solution for single-phase flow. The computed results show the formation of a CVP and horseshoe vortices, which are convected downstream. LES also reveals the intermittent formation of upright wake vortices from the horseshoe vortices oil the ground toward the CVP. The dispersion of polydisperse spray droplets is computed using the stochastic parcel method. Atomization and droplet breakup are modeled by a combination of the breakup model by Reitz and the Taylor analogy breakup model (see Caraeni, D., Bergstrom, C., and Fuchs, L., 2000, Flow, Turbid. Combust., 65(2), pp. 223-244). Evaporation and droplet collision are also modeled. The flow solver uses two-way coupling. Averages of the velocity and gaseous fuel mass fraction are computed. The single-phase JICF is validated against experimental data obtained by PIV. Additionally, the PDFs and frequency spectra are presented.
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