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수평 배플이 설치된 사각 용기 내 슬로싱의 입력성형 기반 제어
정석민(S. Jeong),김동주(D. Kim) 한국전산유체공학회 2021 한국전산유체공학회지 Vol.26 No.1
Suppression of liquid sloshing in moving tanks is essential in many engineering applications. The sloshing can be successfully suppressed by installing baffles inside the tank or applying a control theory called ‘input shaping’ to the tank velocity profile. This study aims to numerically investigate the combined effect of horizontal baffles and input shaping on sloshing in a horizontally moving tank. Numerical simulations are carried out for the two-phase flow of water and air using a volume-of-fluid(VOF) model. Results show that the damping effect of baffles strongly depends on the baffle height but input shaping provides additional control capability for all the baffle heights considered.
Si(5 5 12)-2×1 표면에 벤젠과 피리딘의 결합구조
장상훈(S. H. Jang),오승철(S. Oh),한재량(J. R. Hahn),정호진(H. Jeong),정석민(S. Jeong) 한국진공학회(ASCT) 2006 Applied Science and Convergence Technology Vol.15 No.1
Si(5 5 12)-2×1 표면에 벤젠과 피리딘의 흡착구조를 80 K 온도에서 주사 터널링 현미경과 density functional theory 계산 방법으로 연구했다. 벤젠 분자는 기울어진 butterfly 형태로 Si(5 5 12)-2×1의 D2, D3 유닛에 두 개의 adatom과 강하게 결합된다. 흡착 벤젠 분자에 두개의 C=C 이중 결합이 있으며 탄소와 Si adatom 사이에 di-σ 결합이 있다. 피리딘 분자는 Si-N dative 결합 또는 di-σ 형태로 D2와 D3 유닛의 adatom과 결합을 한다. 질소 원자의 홀전자쌍에 의해 결합된 dative 결합은 수직 형태의 구조를 띠며 di-σ 결합보다 더 안정한 것으로 나타났다. Di-σ 결합은 Si-C2와 Si-C5 또는 Si-N1와 Si-C4으로 형성된다. We investigated the adsorption of benzene and pyridine on Si(5 5 12) -(2x1) at 80 K by using variable-low temperature scanning tunneling microscopy (STM) and density functional theory (DFT) calculations. The benzene molecule most strongly binds to two adatoms on the D3 and D2 units in a tilted butterfly configuration, which consists of di-σ bonds between C atoms and Si adatoms and two C=C double bonds in the benzene molecule. Pyridine molecules interact with adatom(s) on the D2 and D3 units through both Si-N dative bonding and di-σ bonds. The dative bonding through the lone pair electrons of N atom produces a vertical configuration (pyridine-like), which is more stable than di-σ bonds. Di-σ bonds can be formed either through Si-N1 and Si-C4 or Si-C2 and Si-C5.
PARTICLE-LADEN FLOW AROUND TWO CIRCULAR CYLINDERS IN TANDEM ARRANGEMENTS
D.A.H. Khalifa,S. Jeong(정석민),D. Kim(김동주) 한국전산유체공학회 2021 한국전산유체공학회지 Vol.26 No.3
Numerical simulations are performed for particle-laden flow around two circular cylinders in tandem arrangements. The present study aims to understand the effects of cylinder spacing and particle size on particle dispersion and deposition characteristics. We consider the Reynolds number of 100 at which vortex shedding takes place, and the density ratio of particle to fluid is fixed as 1,000. For a parametric study, we vary the Stokes number from 0.1 to 10 for the center-to-center spacing of 2D, 3D, and 4D, where D is the cylinder diameter. As the spacing decreases from 4D to 2D, vortex shedding becomes weaker and lift fluctuations are reduced, agreeing well with the previous results. The dispersion pattern of particles around the cylinder changes significantly depending on the spacing. The overall deposition efficiency of the upstream cylinder is very similar to that of a single cylinder. However, the efficiency of the downstream cylinder has much smaller values with a strong dependency on the spacing. The local deposition efficiency and the deposition location are also analyzed in detail.