Research Topics
1. Hydrodynamics
Boundary Instabiity and vortex street - Von Kármán vortex street has been studied for over a century, but the physical mechanism of the pattern formation and the self-organization of vortices are not fully understood. We explore this classical hydrodynamics problem in a novel approach. Most studies in this area concerned the wake behind a circular cylinder, but such a setting was limited because the circular cylinder has a single length scale. Instead, we independently control two length scales, one being the thickness of the boundary layers and the other being the separation distance between them by using wedges of different angles. For detail, please see PRE 2015 and JFM 2019.
Vortex dynamics in weakly compressible medium - In the classical vortex dynamics, the velocity field is assumed to propagate instantaneously. However, when this assumption fails, i.e. the vorticity field propagates at a finite speed, what would be the vortex arrangement? Currently, it is being actively investigated both theoretically and experimentally.
Computational Fluid Dynamics - While the experiment is my main tool of the research, I am expanding my reach to cover the computational methods.
2. Soft matter, interfacial flow
Why soap films are stable - Soap film is a micron-thin structure of liquid water. It sounds like fragile, but it persists some extent of time. The stability of soap films is due to the elasticity that arises from the thermodynamic action of the surfactants. When the soap film is mechanically stretched, the resultant uneven distribution of surfactants creates uneven Marangoni stress, which tends to dynamically recover the original equilibrium state. We measured the elasticity by inspecting the shock wave formed in the soap films. For detail, please see PRF 2017.
Surface tension of soap films - The surface tension is casually measured by various methods, such as the ring method and the pendant drop method. However, none of these methods are applicable to the surface tension of a liquid film. By using the fluid-structure interaction, we made the first measurement of the surface tension of the soap film. For detail, please see JFM 2018 which is featured in Focus in Fluids.
Simulation of compressible air flow using soap films - Using the similarity of the dynamics of compressible air flow and incompressible soap film, we intend to simulate supersonic flight models using soap films.
Funded by the National Research Foundation of Korea ($600,000, 2021-2026)Impact dynamics between the droplet and the film - While the impact of droplet onto solid surface or liquid bath has been studied many times, the impact of a droplet onto a liquid film was less explored. I conducted the first quantitative study of the collision dynamics between water droplet and a liquid film. The measurements show that the minimum amount of energy is required when the thickness of the film approaches zero, and the deformation of the film is responsible for the energy requirement. For detail, please see PRE 2010.
3. Jet engine
Supercritical fuel injection - In collaboration with a team in the Agency for Defense Development in South Korea, I am investigating a scenario in which the fuel of hypersonic vehicle absorbs a substantial amount of external heat. These experiments are focused on the quantification of fuel discharge and the characterization of its injection pattern at various temperatures and pressures, covering the liquid, gaseous, multi-, and supercritical phases.
연구과제 수행 현황
수행중
2021/3-2026/8 연구재단 우수신진연구
2차원 비누막을 이용한 초음속 램제트 모사에 대한 연구
Simulation of supersonic ramjet using two-dimensional soap films
수행완료
2022/5-2023/4 건국대학교 KU학술연구비
소멸하는 거품의 크기 분포
Transient size distribution of merging bubbles2019/10-2021/2 건국대학교 신임교원연구비
삼각형 물체 뒤에 관찰되는 2차원 층류 와류의 형상에 대한 연구
On the morphology of two-dimensional laminar vortex streets behind triangles