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Aeroacoustics using LES of Turbulent Flows around an Airfoil
Takeo Kajishima,Changhwa Han 한국전산유체공학회 2014 한국전산유체공학회 학술대회논문집 Vol.2014 No.11
To development an efficient indirect method for aeroacoustic field, a numerical method for turbulent flows at low Mach number and a sound source model are discussed. The time marching method for the usual incompressible scheme is modified to account for the weak compressibility. A one-equation subgrid scale model (SGS) for the large-eddy simulation (LES) is improved to deal with high Reynolds number flows appropriately. The reproduced turbulent flow around NACA0012 airfoil is in good agreement with experimental data The sound source formulation is derived by rearranging the continuity and Navier-Stokes equations to the wave motion equation. The investigation using LES database of flow around NACA0012 airfoil suggests that the material derivative of the velocity divergence plays a dominant role as a sound source. The distribution of the sources is consistent with of the classical sound source model such as Lighthill or Powell in case of very low fluctuation of density. The sound pressure level predicted based on the above-mentioned LES and newly derived sound source model is in reasonable agreement with experimental data.
Formation and characterization of MEH-PPV/PCBM-based bulk heterojunction solar cells
Takeo Oku,Syuichi Nagaoka,Atsushi Suzuki,Kenji Kikuchi,Yasuhiko Hayashi,Hayato Sakuragi,Tetsuo Soga 한양대학교 세라믹연구소 2008 Journal of Ceramic Processing Research Vol.9 No.6
Polymer/fullerene bulk heterojunction solar cells with poly[2-methoxy-5-(20-ethylhexoxy)-1,4-phenylenevinylene] (MEH-PPV), zinc-phthalocyanine (ZnPc) and 6,6-phenyl C61-butyric acid methyl ester (PCBM), were produced and characterized. A device based on MEH-PPV and PCBM provided better efficiency, fill factor and short-circuit current compared to those of a device on MEH-PPV(ZnPc) and PCBM. The solar cells with a MEH-PPV and PCBM structure showed a higher photoresponse in the range of 300 to 60 nm. The energy levels of the molecules were calculated and are discussed. Polymer/fullerene bulk heterojunction solar cells with poly[2-methoxy-5-(20-ethylhexoxy)-1,4-phenylenevinylene] (MEH-PPV), zinc-phthalocyanine (ZnPc) and 6,6-phenyl C61-butyric acid methyl ester (PCBM), were produced and characterized. A device based on MEH-PPV and PCBM provided better efficiency, fill factor and short-circuit current compared to those of a device on MEH-PPV(ZnPc) and PCBM. The solar cells with a MEH-PPV and PCBM structure showed a higher photoresponse in the range of 300 to 60 nm. The energy levels of the molecules were calculated and are discussed.