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반전된 깃발의 운동패턴에 작용하는 유동 상류의 둔각물체의 영향
김현성(Hyeonseong Kim),김준영(Junyoung Kim),김대겸(Daegyoum Kim) 한국가시화정보학회 2015 한국가시화정보학회 학술발표대회 논문집 Vol.2015 No.12
Flow-induced vibration of flexible structures for energy harvesting has drawn attention recently. An inverted flag whose trailing edge is clamped and leading edge is free to move was known to self-excite in a uniform flow of both water and air. In this study, we investigated the effect of an upstream bluff body, a flat plate, on the dynamic of the downstream inverted flag. We examined the motion of the inverted flag by varying the relative displacement of the inverted flag from the bluff body. Our results show that the inverted flag can flap with higher frequency and larger amplitude with the upstream bluff body. In order to better understand the dynamics of the flag, the analysis of the flow patterns was conducted.
김현성(Hyeonseong Kim),김준수(Junsoo Kim),김대겸(Daegyoum Kim) 대한기계학회 2018 대한기계학회 춘추학술대회 Vol.2018 No.12
Bi-stability of the elastic structures have been investigated in order to utilize their two equilibrium states and kinetic energy of the structures when transited one state to other rapidly. Here, we investigated one of the typical structural phenomenon, snap-through, which can be observed in a buckled elastic sheet with an external load. We put the sheet in parallel with a uniform flow acting as the external load and measure critical velocity where the buckled beam transitions from one side to another. Theoretical analysis using force balance between the forces and wind tunnel experiments were conducted. Additionally, in order to study the effect of mass ratio on the stability of the elastic sheet, water tunnel experiments were also conducted.
두 반전된 깃발의 균일 유동 내에서의 자가 진동 패턴 연구
김현성(Hyeonseong Kim),강소현(Sohyeun Kang),김대겸(Daegyoum Kim) 한국가시화정보학회 2016 한국가시화정보학회 학술발표대회 논문집 Vol.2016 No.4
Flutter instability has been studied to understand flapping patterns about thin plates or sheets. An inverted flag whose trailing edge is clamped in a uniform flow was known to alter its dynamics dramatically at a critical free-stream velocity. In this study, we investigated the interaction of two inverted flags whose fixed ends are symmetrically placed with respected to the vertical middle line of the flow zone. We examined flapping patterns of the two inverted flags by varying the relative gap between the two flags and aspect ratio of the flags. Our results show that the aspect ratio and the gap alter there critical free-stream velocity at which flutter instability occurs. Also we found several flapping modes : in phase flapping mode, out of phase flapping mode, attached mode, depending on there aspect ratio and a gap between them.
김준영(Junyoung Kim),김현성(Hyeonseong Kim),김대겸(Daegyoum Kim) 대한기계학회 2015 대한기계학회 춘추학술대회 Vol.2015 No.11
We investigated experimentally self-excited vibration of an array of cylindrical pendulums in a uniform flow in order to find its potential application to energy harvesting. A cylindrical pendulum is fixed to a rigid upper plate via a thin elastic sheet so that it can swing perpendicularly to the free stream. Although this type of model has been studied for electrical energy generation, few studies have been conducted in order to understand the detailed physics of fluidstructure interaction. In this study, the flow pattern and dynamics of pendulums were examined by varying distance among the pendulums and free-stream fluid velocity. The interaction of an upstream bluff body and pendulums was also considered to investigate how the wake of the bluff body affects the oscillations of cylinders. With this experimental setup, the pendulums show various patterns such as stationary mode and out-of-phase oscillation mode.
자유유동 내에서의 원주형 진자의 유체-구조 연성에 대한 연구
김준영(Junyoung Kim),김현성(Hyeonseong Kim),김대겸(Daegyoum Kim) 한국가시화정보학회 2015 한국가시화정보학회 학술발표대회 논문집 Vol.2015 No.12
We investigated experimentally self-excited vibration of an array of cylindrical pendulums in a uniform flow in order to find its potential application to energy harvesting. A cylindrical pendulum is fixed to a rigid upper plate via a thin elastic sheet so that it can swing perpendicularly to the free stream. Although this type of model has been studied for electrical energy generation, few studies have been conducted in order to understand the detailed physics of fluid-structure interaction. In this study, the flow pattern and dynamics of pendulums were examined by varying distance among the pendulums and free-stream fluid velocity. The interaction of an upstream bluff body and pendulums was also considered to investigate how the wake of the bluff body affects the oscillations of cylinders. With this experimental setup, the pendulums show various patterns such as stationary mode and out-of-phase oscillation mode.