A5088515276- Fluid Dynamics and Turbulent Flows
- Wind and Air Flow Studies
- Particle Dynamics in Fluid Flows
- Aerodynamics and Fluid Dynamics Research
- Plant Water Relations and Carbon Dynamics
- Railway Engineering and Dynamics
- Fluid Dynamics and Vibration Analysis
- Heat Transfer Mechanisms
- Engineering Applied Research
- Vehicle emissions and performance
- Reservoir Engineering and Simulation Methods
- Meteorological Phenomena and Simulations
- Fluid Dynamics and Heat Transfer
- Hydrology and Sediment Transport Processes
- Brake Systems and Friction Analysis
- Cyclone Separators and Fluid Dynamics
- Evacuation and Crowd Dynamics
- Icing and De-icing Technologies
- Fluid Dynamics Simulations and Interactions
- Nanofluid Flow and Heat Transfer
- Winter Sports Injuries and Performance
- Rocket and propulsion systems research
- Railway Systems and Energy Efficiency
- Heat transfer and supercritical fluids
- Computational Fluid Dynamics and Aerodynamics
Korea National University of Transportation
2021-2024
Korea Institute of Atmospheric Prediction Systems
2021
Yonsei University
2021
Korea Advanced Institute of Science and Technology
2013-2019
Agency for Defense Development
2019
A direct numerical simulation of a turbulent pipe flow at high Reynolds number Reτ = 3008 over long axial domain length (30R) was performed. The streamwise mean velocity followed the power law in overlap region (y+ 90–300; y/R 0.03–0.1) based on indicator function. scale separation shear stresses into two components small- and large-scale motions (LSMs) revealed that LSMs outer played an important role constructing constant-stress layer velocity. In pre-multiplied energy spectra...
The relationship between the frictional drag and velocity-vorticity correlations in wall-bounded turbulent flows is derived from mean vorticity equation. A formula for skin friction coefficient proposed evaluated with regards to three canonical flows: boundary layer, channel flow, pipe flow. encompasses four terms: advective transport, vortex stretching, viscous, inhomogeneous terms. Drag-reduced flow slip condition used test reliability of formula. transport stretching terms are found...
Statistical measures of turbulence intensities in turbulent pipe and channel flows at a friction Reynolds number Reτ ≈ 930 were explored by population large-scale motions (LSMs) very-large-scale (VLSMs). Although the statistical characterizing these internal similar near-wall region, extents mean streamwise velocities cross-stream components differed core region. The density VLSMs/LSMs decreased/increased significantly region flow. survival time VLSMs flow was shorter than that area...
A direct numerical simulation of a spatially developing turbulent boundary layer with large-eddy breakup (LEBU) device was performed to investigate the influence LEBU on near-wall turbulence and frictional drag. The device, which is thin rectangular in shape, located at 80% thickness (δ). reduced skin-friction coefficient (Cf) up 17%. breakdown outer structures passing through energy long wavelength motions (λz+>200) along wall-normal direction. reduction Cf mainly arose from...
Direct numerical simulation data for turbulent minimal pipe flows with Reτ = 927, 1990, and 2916 are examined to explore the azimuthal (or spanwise) organization of their large-scale structures. We chose a streamwise-minimal unit streamwise domain length Lx+≈1000, which is characteristic near-wall streaks. The spanwise scales most energetic motions contributions total energy comparable those long-domain simulation. In spectra velocity fluctuations (u), increases three outer peaks (λθ...
Direct numerical simulations of differentially heated vertical channel (DHVC) flows were performed for Ra=105–109 to investigate the characteristics streamwise mean momentum and thermal energy equations. The log law temperature was observed Ra≥108 at y+>50, where y+ is wall-normal distance normalized by viscous wall unit. From equation, negligible force logarithmically increasing Reynolds shear stress in region occurred. velocity did not exhibit a linear relationship with close show...
The statistical relationships among the turbulence structures of streamwise velocity fluctuations along and azimuthal directions in a turbulent pipe flow were examined using direct numerical simulation data at Reτ = 3008. Two-point correlations showed linear relationship between length scales (lx lθ), where lθ/lx 0.07 wall-normal distance, indicating long coherent called very-large-scale motions (VLSMs). one-dimensional pre-multiplied energy spectra that wavelengths (λx λθ) grew linearly...
The characteristics of vortical structures in T-shaped branches with respect to the shear-thinning effect are numerically investigated using a power-law fluid model. By varying index n, we observe three different flow structures, namely, steady-, harmonic-, and turbulent-like regimes. time-averaged instantaneous examined for values local Reynolds number. In steady regime, stationary form near corners branch. As n decreases, oscillate back forth, giving rise harmonic regime. Decreasing...
본 연구에서는 비정상 대와류모사 해석을 수행하여 430 km/h의 높은 속도 유동을 마주하는 팬터그래프의 주위 모사하였다. 팬터그래프는 링크 구조로서 공기역학적 압상력을 정확하게 예측하기 위해서는 팬터그래프가 받는 항력과 양력을 모두 고려해야한다. 각 구조물이 구조의 힘과 모멘트 평형 관계식에 대입하여, 전차선에 가해지는 도출하였다. 팬터그래프 하단부 커버가 있는 경우에 대해서도 동일한 수행하여, 미치는 영향을 살펴보았다. 그 결과, 경우 아래 방향으로 받으며, 없는 경우보다 전체 양력이 줄어든다. 이로 인해 압상력 또한 감소한다. 그러나 경우, 압상력의 표준편차 값이 감소하여, 집전 성능 향상에 기여할 수 있다.