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Effects of Fluid-Structure Interaction on the Trailing-Edge Noise
Youngmin Bae,Jae Jang,Young Moon 대한기계학회 2008 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.22 No.7
This study numerically investigates the effects of fluid-structure interaction (FSI) on the trailing-edge noise, particularly for the cases of wake instability and Karman vortex shedding. The trailing edge is modeled as a flat plate with an elastic cantilever end and its flow-induced vibration is solved by an eigenmode analysis with the Galerkin method. The flow and sound coupled in the FSI analysis are computed on the moving grid by a direct numerical simulation (DNS) procedure. The computed result of wake instability shows that when the first-eigenmode natural frequency ωn of the cantilever is close to be resonant with the wake characteristic frequency ωc, the sound pressure level (SPL) is significantly reduced by 20 dB at ωn/ωc=0.95, or increased by 15 dB at ωn/ωc=1.05, for all angles. For the Karman vortex shedding, a similar frequency modulation occurs via FSI, if ωn is close to ωc. The flow and acoustic details are somewhat different for this case but a considerable noise reduction was also possible for angles from -120º to +120º.
Transient performance analysis of pressurized safety injection tank with a partition
Bae, Youngmin,Kim, Young In,Kim, Keung Koo Elsevier 2015 Annals of nuclear energy Vol.75 No.-
<P><B>Abstract</B></P> <P>A parametric study has been performed to evaluate the functional performance of a pressurized multi-unit safety injection tank, which would be considered as one of the candidates for a passive safety injection system in a nuclear power plant. The influences of key design parameters including the orifice size, initial gas fraction, and resistance coefficients and operating condition on the injection flow rate are scrutinized with a discussion of the relevant flow features such as the choked flow of gas through an orifice and two interconnected regions of differing gaseous pressure. The obtained results indicate that a multi-unit safety injection tank can passively control the injection flow rate and provide a stable safety injection over a relatively long period even in the case of drastic depressurization of a reactor coolant system.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Functional performance of safety injection tanks with a partition is evaluated. </LI> <LI> Effects of key design parameters are scrutinized. </LI> <LI> Distinctive features of the flow in multi-unit safety injection tanks are explored. </LI> </UL> </P>
Numerical Analysis of Thermal Development of Laminar Flow in a Concentric Multilayer Annulus
Bae, Youngmin,Kim, Seong H.,Seo, Jae‐,Kwang,Kim, Young‐,In VCH VERLAGSGESELLSCHAFT 2014 CHEMICAL ENGINEERING AND TECHNOLOGY Vol.37 No.1
<P><B>Abstract</B></P><P>The thermal behavior of laminar flow in a concentric multilayer annulus is investigated numerically for varying dimensionless inner radii and a defined number of fluid layers. Under a hydrodynamically developed flow assumption within the fluid layers, the development of temperature profiles and heat transfer along the annulus are analyzed for two different boundary conditions. The mean temperature distribution, local Nusselt number, and mean Nusselt number are discussed in detail with an emphasis on the effects of the inner radius and number of fluid layers. The obtained results indicate that the change in heat transfer coefficient in a layered annulus is more pronounced at a small inner radius or larger radius ratio. A further insertion of more than ten layers has insignificant influence on the convective heat transfer in a layered annulus.</P>
배영민(Youngmin Bae),문영준(Young J. Moon) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.5
This study numerically investigates the unsteady flow and acoustic characteristics of a flapping wing using a hydrodynamic/acoustic splitting method. The Reynolds number based on the maximum translation velocity of the wing is Re=8800 and Mach number is M=0.0485. The flow around the flapping wing is predicted by solving the two-dimensional incompressible Navier-Stokes equations (INS) and the acoustic field is calculated by the linearized perturbed compressible equations (LPCE), both solved in moving coordinates. Numerical results show that the hovering sound is largely generated by wing translation (transverse and tangential), which have different dipole sources with different mechanisms. As a distinctive feature of the flapping sound, it is also shown that the dominant frequency varies around the wing.
Enhanced Stability of Coated Carbon Electrode for Li-O<sub>2</sub> Batteries and Its Limitations
Bae, Youngjoon,Ko, Dong-Hyun,Lee, Sunyoung,Lim, Hee-Dae,Kim, Yun-Jung,Shim, Hyun-Soo,Park, Hyeokjun,Ko, Youngmin,Park, Sung Kwan,Kwon, Hyuk Jae,Kim, Hyunjin,Kim, Hee-Tak,Min, Yo-Sep,Im, Dongmin,Kang, Wiley (John WileySons) 2018 ADVANCED ENERGY MATERIALS Vol.8 No.16