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사각 밀폐계 내 자연대류에 의한 원형 실린더의 운동 특성에 관한 수치적 연구
손성완(S. W. Son),정해권(H. K. Jeong),윤현식(H. S. Yoon),하만영(M. Y. Ha) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.11
The present study numerically investigates the motion of a solid body suspended in the square enclosure with natural convection. A two-dimensional circular cylinder levitated thermally has been simulated by using thermal lattice Boltzmann method (TLBM) with the direct-forcing immersed boundary method. To deal with the ascending, falling or levitation of a circular cylinder in natural convection, the immersed boundary method is expended and coupled with the TLBM. The circular cylinder is located at the bottom of a square enclosure with no restriction on the motion and freely migrates due to the Boussinesq approximation which is employed for the coupling between the flow and temperature fields. For different density ratio between the cylinder and the fluid, the motion characteristics of the circular cylinder for various the Grashof number have been carried out. The Prandtl number is fixed at 0.7.
동조질량감쇠기를 이용한 비공진 대역에서의 진동 감소 연구
배수룡(Soo Ryong Bae),정우진(Woo-Jin Jung),한현희(H. H. Han),손성완(S. W. Son) 한국소음진동공학회 2016 한국소음진동공학회 학술대회논문집 Vol.2016 No.4
Submarine is detected by its underwater radiated noise. Machinery is major source of underwater radiated noise of submarine. Generally submarines are designed to not be identical between exciting frequencies of machinery and resonant frequency of structure. This paper presents the trade-off study for tuned mass damper(TMD) which is tuned off resonance frequency of structure to be controlled, tuned in non-resonance bandwidth for applying submarine. The vibration attenuation effect of structure with TMD is verified experimentally in case of TMD on and off. TMD which is tuned in non-resonance bandwidth shows the vibration reduction and response change of structure.
서로 다른 세가지 접촉각을 가지는 이질표면 위에 존재하는 액적의 거동에 관한 3차원 수치해석 연구
이경훈(K.H. Lee),손성완(S.W. Son),김형락(H.R. Kim),하만영(M.Y. Ha) 대한기계학회 2015 대한기계학회 춘추학술대회 Vol.2015 No.11
The behavior of the semi-spherical droplet existing on a heterogeneous surface was researched using a 3-D Lattice Boltzmann method. In this paper, the behavior of droplet studied that it is affected by contact angle of surface and size of droplet. The droplet locates on the heterogeneous surface, which includes hydrophilic and hydrophobic. In this paper, contact angle of hydrophilic range is from 20 to 70 and contact angle of hydrophobic is consisted of 140 and 150. As time goes by droplet shows three different patterns. If the difference of contact angle between hydrophobic and hydrophilic surface is small that the droplet doesn’t easily separate. And the droplet reaches a new equilibrium state on the heterogeneous surface. And effect of size of droplet shows two phenomena. If the droplet size becomes bigger, the behavior of droplet is shown that whole droplet spread out over the hydrophilic surface. On the other hands size of droplet becomes smaller that it is separated two droplets. In other words there is an effect of size about the behavior of droplet. The droplet separation mechanism is investigated by analyzing the velocity vector around the phase boundary. The temporal volume fraction and temporal vector field which vary by time were shown for each case carried out. And the time spent for dividing the droplet into two droplets was calculated.
격자 볼츠만 법을 이용한 이질표면 위에 존재하는 액적의 크기 변화에 따른 거동의 3차원 수치해석 연구
최호연(H.Y. Choi),손성완(S.W. Son),하만영(M.Y. Ha) 대한기계학회 2015 대한기계학회 춘추학술대회 Vol.2015 No.11
The characteristic of the droplet located on a heterogeneous surface is numerically analyzed using the 3-D Lattice Boltzmann Method(LBM). LBM is having an advantage of the two phase flow. Predictions are made whether the droplet will be separated or not. The separation time is affected according to changes of the contact angles of the hydrophilic and hydrophobic surface, and the droplet size. The droplet separation mechanism is investigated by analyzing the velocity vector around the phase boundary line and shape of the droplet. If the difference between the contact angles of the hydrophilic and hydrophobic surfaces is bigger, a droplet located at the center of a heterogeneous surface shows a trend of being easily separated. The droplet separation time increases according to the decrease of contact angle of hydrophobic surface, and the more the contact angle of the hydrophobic surface increases, the more the droplet separation time decreases. Also, the droplet separation time shows a decreasing trend when the droplet size decreases. Furthermore, the result show that separation time and the map of droplet separation changed with respect to the droplet size.