http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Thermal effect on large-aspect-ratio Couette–Taylor system: numerical simulations
Kang, Changwoo,Yang, Kyung-Soo,Mutabazi, Innocent Cambridge University Press 2015 Journal of fluid mechanics Vol.771 No.-
<P>We have performed numerical simulations of the flow in a large-aspect-ratio Couette–Taylor system with rotating inner cylinder and with a radial temperature gradient. The aspect ratio was chosen in such a way that the base state is in the conduction regime. Away from the endplates, the base flow is a superposition of an azimuthal flow induced by rotation and an axial flow (large convective cell) induced by the temperature gradient. For a fixed rotation rate of the inner cylinder in the subcritical laminar regime, the increase of the temperature difference imposed on the annulus destabilizes the convective cell to give rise to co-rotating vortices as primary instability modes and to counter-rotating vortices as secondary instability modes. The space–time properties of these vortices have been computed, together with the momentum and heat transfer coefficients. The temperature gradient enhances the momentum and heat transfer in the flow independently of its sign.</P>
파이프 유동에서의 난류물질전달에 대한 Schmidt 수의 영향
강창우(Changwoo Kang),양경수(Kyung-Soo Yang) 대한기계학회 2012 대한기계학회 춘추학술대회 Vol.2012 No.11
Large Eddy Simulation (LES) of turbulent mass transfer in circular-pipe flow has been performed to investigate the effects of Schmidt number on turbulent mass transfer. We consider a fully developed turbulent pipe flow with a constant wall concentration. The Reynolds number under consideration is Re<SUB>τ</SUB>=500 based on the friction velocity and the pipe radius, and the Schmidt numbers are 0.71, 5, 10, 20 and 100. Dynamic subgrid-scale(SGS) models for turbulent SGS stresses and mass fluxes are employed to close the governing equations. In this investigation, we examine the reliability of the LES technique for predicting turbulent mass transfer at high-Schmidt numbers and analyze the behavior of turbulent mass diffusion from the wall at different Schmidt numbers. To show the effects of Schmidt number on turbulent mass transfer, the statistical quantities such as mean concentration profiles, concentration variance, turbulent mass fluxes, turbulent Schmidt number, and mass transfer coefficients are presented for the selected Schmidt numbers. Turbulence budgets for concentration variance and turbulent mass fluxes are computed and the effect of Schmidt number is identified. In addition, to clarify the correlation between near-wall turbulence structures and concentration fluctuation, we report an Octant analysis in the vicinity of the pipe wall.
영변 핵시설의 기술적 가치 평가: 북한의 핵무기 현대화를 중심으로
강창우 ( Kang Changwoo ) 한국국가전략연구원 2022 한국국가전략 Vol.7 No.3
This paper argues that activities at Yongbyon nuclear facilities are closely related to North Korea's advanced nuclear weapons and quality improvement. Now, the value of Yongbyon goes beyond simply producing nuclear materials to increase the number of nuclear warheads. This paper explains that Yongbyon has important technical and physical values to meet North Korea's strategic needs. Therefore, it is necessary to evaluate the future technological value of Yongbyon to achieve North Korea's strategic intentions in the future by breaking away from the political and diplomatic perspective for bargaining chip focused on its past capabilities. Modernizing North Korea's nuclear weapons requires the development of various tactical nuclear weapons, hydrogen bomb development and additional production, nuclear submarine development, and warhead safety and credibity. From this point of view, Yongbyon's nuclear material production and technological activities can contribute to the quality improvement of nuclear modernization rather than simply producing nuclear materials to increase the number of nuclear warheads, which emphasizes that Yongbyon has an important technological value in achieving North Korea's strategic intentions in the future.