전단 유동에서 액적의 거동에 관한 수치적 연구

서영호(Youngho Suh),이창훈(Changhoon Lee) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5

Numerical simulation is performed for a droplet behavior in a linear shear flow. The liquid-air interface is tracked by level set method, which is improved by incorporating a sharp-interface modeling technique for accurately enforcing the matching conditions at the liquid-gas interface. The computations are carried out to investigate the rotation and deformation behavior of droplet derived by the simple linear shear flow. In the computation, the numerical results for the effects of droplet size, shear rate and liquid properties on the droplet motion are presented.

미세액적의 자기정렬 기법을 포함한 패터닝 공법에 대한 해석적인 연구

서영호(Youngho Suh),손기헌(Gihun Son) 대한기계학회 2009 大韓機械學會論文集B Vol.33 No.1

Numerical simulation is performed for microdroplet deposition on a pre-patterned micro-structure. The liquid-air interface is tracked by a level-set method, which is improved by incorporating a sharp-interface modeling technique for accurately enforcing the matching conditions at the liquid-gas interface and the no-slip condition at the fluid-solid interface. The method is further extended to treat the contact angle condition at an immersed solid surface. The present computation of a patterning process using microdroplet ejection demonstrates that the multiphase characteristics between the liquid-gas-solid phases can be used to improve the patterning accuracy.

피드백 힘을 이용한 전단유동에서 액적의 항력 및 양력 계산에 관한 수치적 연구

서영호(Youngho Suh),이창훈(Changhoon Lee) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11

The droplet behavior in the linear shear flow is determined by a level set method which is improved by incorporating a sharp-interface modeling technique for accurately enforcing the matching conditions at the liquid-gas interface. To determine the acting force on a droplet in shear flow field, the feedback forces which can maintain droplet position were adopted for efficient handling of deformation. Computations were carried out to investigate the effects of deformation of a droplet on drag and lift forces with various shear rate and dimensionless parameters. Based on the numerical results, drag and lift forces acting on a droplet are observed to depend strongly on the deformation. Also, the present method is proven to be applicable to a three-dimensional deformation of droplet in the shear flow, which cannot be properly analyzed by the previous studies.

피에조 잉크젯에서 액적분사 현상에 관한 수치적 연구

서영호(Youngho Suh),손기헌(Gihun Son) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5

A numerical method is presented for computing the droplet ejection through a micro nozzle in piezoelectric inkjet process. A finite difference method is used to solve the conservation equations for mass and momentum. The liquid-air interfaces are tracked by a level set method which is extended to treat the contact angle condition at an immersed solid surface. The boundary conditions at the interfaces are accurately imposed by incorporating the ghost fluid approach based on a sharp-interface representation. The numerical method is applied to analyze the effects of pressure pulse, nozzle shape and contact angle on droplet ejection and formation.

전단유동에서 변형하는 액적의 항력 및 양력 계산

서영호(Youngho Suh),이창훈(Changhoon Lee) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.10

징후와 발견의 라이트모티프 소리망

서영호(Youngho Suh) 글로벌문화콘텐츠학회 2024 글로벌문화콘텐츠 Vol.- No.58

현대 영화음악에서 라이트모티프를 활용한 반복과 변주의 기법은 매우 보편적인 것이 되었다. 특히 스릴러, 공포 장르의 영화에서 그것은 더 두드러지는데 이러한 점에서 영화 <싸인>의 음악은 주목할만한 사례다. 단 3개의 음으로 된 모티프의 반복과 변주로 영화의 거의 모든 장면을 이끌어 가며 ‘징후과 발견’이라는 영화 서사에 조응하는 소리망을 구축하고 있다는 점에서, <싸인>의 음악은 현대 영화음악에서의 모티프 활용의 극단을 보여주는 사례이며 이 연구는 그 소리구조와 서사의 상호성을 살핀다. 영화의 분석에 앞서 라이트모티프에 대한 그간의 논의를 취합, 검토하고 개념과 기능에 관해 이 연구를 위한 전제들을 구상하였다. 영화의 분석을 통해서 신의 계시의 징후를 소리적으로 상징하는 <싸인>의 음악적 모티프가 전조, 음정의 변화, 리듬의 분절을 포함한 템포의 가속과 감속, 배면의 화성 변화, 악기 편성의 변화 등에 의한 복잡성의 증가와 강조 등을 통해 서사에 가담하는 양상을 밝혔다. 선과 악, 혹은 그 사이를 오가는 어떠한 대상으로서 징후의 의미는 음악을 통해 비로소 구체화되며, 그것은 상황을 예고하거나 해설을 더함으로써 영상과의 상호성을 통해 장면을 완성한다. 징후에 대한 깨달음-발견으로 해결되는 영화의 결말에서 음악은 비로소 단절적이고 파편적인 모티프에서 선율을 갖춘 하나의 곡조로 전이되며 신의 메시지의 의미를 온전히 드러낸다. The technique of using leitmotifs for repetition and variation has become widespread in contemporary film music. This is particularly prominent in thriller and horror genres, where the music plays a crucial role in building tension and enhancing the narrative. In this regard, the music of the film Signs stands out as a noteworthy example. It employs a simple three-note motif that repeats and varies throughout almost every scene of the film, creating a musical structure that corresponds to the narrative of ‘signs and recognition’. This is an example that shows the extreme use of motifs, and this article is to analyze the structure of music of Signs as it. Prior to analysis, I collected and reviewed previous discussions on leitmotifs and established premises for this study regarding the concept and function. The leitmotif symbol?izes the signs of the God’s message and engages with the narrative through various musical elements such as modulation, key changes, tempo changes including rhythmic alterations, harmonic shifts, and increase in complexity and emphasis through changes in instrumental arrangements. As the narrative unfolds, the meaning of the signs, whether as the good or evil, or as something that goes between them, become concrete. And the music, by foreshadowing or providing commentary, completes the scene through its interplay with the visuals scenes. At the end of the film, where the revelation about the sign is resolved, the music finally transitions from a concise and simple motif to a melodic unity, finally revealing the full meaning of the God's message.

버블 잉크젯에서의 리필 현상에 관한 수치적 연구

서영호(Youngho Suh),손기헌(Gihun Son) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.10

Numerical simulation is performed for a bubble inkjet process, in which droplet ejection is driven by an evaporating bubble. The liquid-vapor and liquid-air interfaces are tracked by a level set method which is modified to include the effects of phase change and bubble compressibility and is extended to treat the contact angle condition at an immersed solid surface. The whole process of bubble inkjet is simulated without employing a simplified bubble growth model. The present computation demonstrates the inkjet process including jet breaking, satellite droplet formation and ink refill motion as well as bubble growth and collapse.

Level Set과 VOF 방법을 결합한 3차원 경계면 추적법

서영호(Youngho Suh),성명호(Myungho Sung),손기헌(Gihun Son) 대한기계학회 2001 대한기계학회 춘추학술대회 Vol.2001 No.9

A coupled level set and volume-of-fluid (CLSVOF) method is presented for computing three-dimensional incompressible two-phase flows. An efficient interface reconstruction algorithm is implemented for the CLSVOF method. Approximating an interface as piecewise linear in each cell, an explicit relation between the interface configuration and the fluid volume fraction is derived through geometrical description of the fractional volume truncated by the interface. The CLSVOF method is verified to calculate an interfacial curvature accurately as well as to achieve volume conservation during the whole computation period. We apply the method to numerical simulations of bubble sliding on a vertical wall and drop-wall collision.

버블 잉크젯에 관한 수치적 연구

서영호(Youngho Suh),손기헌(Gihun Son) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.11

The droplet ejection process driven by the growth of an evaporating bubble in a bubble inkjet printhead is investigated by numerically solving the conservation equations for mass, momentum and energy. The phase interfaces are tracked by a level set method which is modified to include the effects of phase change at the interface and extended for multiphase flows with irregular solid boundaries. The compressibility effect of a bubble is also included in the analysis to appropriately describe the bubble expansion behaviour associated with the high pressure caused by bubble nucleation. The present computation describes not only droplet formation behavior but also jet breaking and satellite droplet formation. Various heating conditions are tested to investigate their effect on bubble growth and droplet ejection. Based on the numerical results, the jet breaking and droplet formation behaviour is observed to depend strongly on the bubble growth and collapse pattern.

기포성장을 이용한 액적분사에 관한 수치적 연구

서영호(Youngho Suh),김성일(Sungil Kim),손기헌(Gihun Son) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5

The droplet ejection process driven by the growth of an evaporating bubble in a micro nozzle is investigated by numerically solving the conservation equations for mass, momentum and energy. The phase interfaces are tracked by a level set method which is modified to include the effects of phase change at the interface and extended for multiphase flows with irregular solid boundaries. Based on the numerical results, the jet breaking and droplet formation behavior is observed to depend strongly on the bubble growth pattern. Various heating conditions are tested to investigate their effect on droplet formation associated with bubble growth.