Flow jets control based on deep reinforcement learning to improve hydrofoil propulsion.

(Main investigator: Taekyeong Jeong)
In nature, birds, insects, and aquatic animals evolved wings and fins to control their movements in complex fluid environments, maintaining precise postures and obtaining efficient propulsion. Inspired by evolution, as part of research on active flow control(AFC), we are conducting a study on improving the propulsion of hydrofoils by applying flow jets. We use deep reinforcement learning(DRL) models for the real-time fine-tuning flow jets on hydrofoils under various flow conditions. This research will be devoted to improving propulsion in underwater vehicles, aircraft wings, and turbine blades, similar to the foil shape.

Rearrangement of plumed seed-inspired poroelastic cluster

(Main investigator: Minhyeong Lee)
Plumed seeds, such as dandelion or milkweed seeds, are wind-dispersal seeds that passively fly by the wind. While other types of wind-dispersal seeds disperse a few hundred meters at maximum, plumed seeds can fly a distance of kilometers. Augmenting counter-gravity drag force is essential for the long-distance dispersion, and the drag is significantly affected by the configuration of a flier. The plumed seed consists of many microscopically thin hairs, which makes the structure porous and elastic, i.e. poroelastic. We adopt a simplified poroelastic cluster to investigate fluid-dynamic mechanisms underlying the long-distance flight of poroelastic seeds. In opposite to common fixed plants that change their shapes to reduce the frontal area encountering the flow, the poroelastic cluster rearranges its constituents to enlarge the frontal area, thereby effectively augmenting the drag force. Moreover, the identification of an optimal porosity that maximizes the drag force has the potential to inform the design of micro-sized drones or wind-dispersal sensors.



Flapping dynamics of an elastically connected multi-segmented structure

(Main investigator: Minho Song)
Regarding the flapping motion of drag-based propulsion, the deforming profile of the propulsion unit act as a critical factor in determining the thrust performance. Proposing a structure composed of rigid segments connected via elastic hinges as a propulsion unit, the passive deflection of the structure by its fluid-structure interaction during periodic flapping motion and the generated hydrodynamic forces are investigated experimentally. Appropriate expressions of the stiffness and deflection of the structure are developed that well characterizes the behavior of the multi-segmented structure. Furthermore, an analytical model is proposed that estimate the unsteady deformation and propulsive forces of the structure.

Thrust generation of multiple entities with cooperative motion

(Main investigator: Dohyun Kim)
Numerous marine creatures, including jellyfish and squid, employ suction and blowing flows as their propulsion strategy. They share common characteristic: a deformable body that enables cyclic contraction and expansion. Drawing inspiration from the coordinated behavior observed in swarms, where multiple entities act like a single unit, we conducted numerical investigation on 2D cylinder array. Each cylinder has simple oscillation to achieve volume changes without any actual deformation. Consequently, we identified the optimal condition that maximizes the thrust generated by the coordinated motion. This research can provide a basis for the development of propulsion and fluid transport methodologies suitable for highly viscous environments, including small-scale Autonomous Underwater Vehicles (AUVs).

Reconfiguration of a bio-inspired leg structure with elastic hinges

(Main investigator: Minho Song) doi:10.1017/jfm.2022.970
For the development of a bio-inspired underwater swimmer with a flexible body, analytical modeling of its dynamics enables comprehensive understanding of the system of interest and can be further utilized to better design propulsion strategies and optimize dynamical behaviors. A feather-like elastic leg structure motivated by feather stars (marine animal) is fabricated, which consists of an elastic shaft and rigid barbs elastically connected to the shaft. Shape reconfiguration of the elastically hinged leg structure under translating motion is experimentally investigated, and a simplified analytical model is developed to estimate the deformation and propulsive force of the structure.

Deep learning model inspired by lateral line system for underwater object detection

(Main investigator: Taekyeong Jeong) doi:10.1088/1748-3190/ac3ec6
Various aquatic animals possess a lateral-line system. The lateral line system detects the movement, vibration, and pressure gradients of the water surrounding the animal, providing spatial awareness and the ability to navigate the environment. Inspired by this lateral line, we propose an object identification model based on deep learning. Through this research, we establish a sensory data-based framework to develop novel navigating and object detecting systems of an autonomous underwater vehicle that can maintain high stability even in abnormal (very narrow, turbid, dark) environmental situations.

Starting jet formation through eversion of elastic sheets

(Main investigator: Cheolgyun Jung)
Motivated by biological systems, such as human hearts and the propulsors of aquatic creatures, the interaction between deformable structures and fluid jets has drawn considerable attention to understand the mechanism of effective fluid transport through such jets. In this study, a novel structure that produces a fast jet with a high hydrodynamic impulse through its large elastic deformation, namely an everting structure, is proposed; the eversion of a structure refers to the process of turning the structure inside out. This study offers insights into the design of medical devices for delivering fluids rapidly as a focused jet at once, such as in the treatment of total occlusions in blood vessels or transdermal drug delivery.

Vortex ring formation coupled with a translating bluff body

(Main investigator: Minho Song)
Motivated by the explosive launch of Sphagnum spores, this experimental study investigates how the vortices generated from two different sources, a piston–cylinder apparatus and a translating bluff body, interact with each other. While the formation of an isolated vortex ring is a popular topic in the field of fluid dynamics, its dynamics during the formation process within vicinity of a moving bluff body remain unexplored. For a certain range of propagation velocity ratio between the vortex ring and the bluff body, the combined vortex structure is capable of transporting a significant fluid volume initially inside the cylinder over a long distance, which shows its effectiveness in transport using a ballistic mechanism.

Aerodynamics of a bristled wing

(Main investigator: Seung Hun Lee)
Unlike the smooth wings of common insects or birds, micro-scale insects such as the fairyfly have a distinctive wing geometry, comprised of a frame with several bristles. Motivated by this peculiar wing geometry, we experimentally investigate the flow structure of a translating comb-like wing for a wide range of gap size, angle of attack and Reynolds number, Re = O(10) – O(10^3), and the correlation of these parameters with aerodynamic performance.



Comparison between flat wing and bristled wing for various Re


Zigzag dynamics of a falling sphere with a filament

(Main investigator : Seungho Choi)
Organisms often utilize passive appendages to enhance their locomotion by effectively manipulating the surrounding flow. These passive appendages play a crucial role in influencing the fluid-dynamic forces around them, making them valuable for various engineering applications. In our experimental study, we investigate the impact of a fiber-shaped appendage on the free-fall dynamics of a sphere. We introduce a model where a filament is attached to the upper hemisphere of the sphere. Interestingly, while the sphere without the filament falls vertically, the filament induces a zigzag motion, causing the sphere to fall more slowly. This intriguing behavior holds the potential for controlling the falling motion of the sphere in practical applications.

Gravity-coupled flutter and contact of a flag near a wall

(Main investigator : Minseop Lee)
The stability and post-critical behaviour of a horizontal flag undergoing gravity-induced deformation and periodic contact with a nearby horizontal rigid wall are experimentally investigated. We propose a horizontal flag model in which the wall is above or below the flag to study the effects of gravity. In general, the behavior of a flag is determined by the relative ratio of the bending force of the flag and the fluid force induced by the uniform flow. However, in a flag model strongly affected by gravity, the mode and behavior of the flag are determined by the relative ratio of the gravitational force and fluid force, and the dynamics of the flag are classified into static, flutter, partial contact, and full contact modes. The results elucidate the combined effects of gravity and contact on flutter and reveal design principles for application to triboelectric energy harvesting.

Flow-induced snap-through dynamics of an elastic sheet

(Main investigator: Hyeonseong Kim)
Snap-through motion, which is a rapid transition from one equilibrium state to another state, can be utilized as a novel mechanism for the flow-induced vibration of an elastic sheet. A post-buckled sheet, which its both ends are clamped, maintains its equilibrium state at low free-stream velocity, and the sheet starts the periodic snap-through oscillation as the free-stream velocity reaches a certain critical velocity. We experimentally and theoretically investigate the critical conditions of the snap-through oscillation as well as the kinematics and kinetics of post-critical oscillation. Furthermore, we employ the principle of periodic snap-through dynamics under fluid flow to develop a novel fluid kinetic energy harvesting system.

Flow-induced vibration and energy harvesting of a cylinder between side walls

(Main investigator: Junyoung Kim)
The dynamics of a cylinder arranged between two side walls are experimentally investigated. The gap between the cylinder and the side walls is sufficiently small to allow the cylinder to impact the walls. In general, a circular cylinder undergoing vortex-induced vibration (VIV) can only oscillate in a limited range of the flow velocity. However, the periodic impact with the side walls allows the large-amplitude oscillations of the impacting cylinder to persist outside of the lock-in region. We devise a novel energy harvesting system based on an impacting cylinder model and a triboelectric nanogenerator (TENG). The impacting cylinder shows improved energy harvesting performance than the non-impacting cylinder.

Prediction of reed valve dynamics based on a deep learning model

(Main investigator: Janggon Yoo)
A reed valve is a type of passive flow controller which regulates flow in a single direction with the deflection of a flexible plate. Interaction between the flexible plate and fluid flow perpendicular to the valve generates a complicated flow structure, and the impact of the plate with a stopper induces nonlinear motion of the plate. We investigate a low-order numerical model to predict the dynamics of the reed valve under periodic pressure pulsation. Furthermore, a deep learning model is established to optimize the performance parameters of the reed value such as mass flux.

Stabilized falling motion of a bio-inspired disk

(Main investigator: Minhyeong Lee)
Some of the smallest insects such as thrips or fairyfly have novel porous wings that consist of many bristles connected to a central frame. Interestingly, these insects not only use their wings to fly actively, but also to parachute passively with no wing stroke. Because it is critical for the fliers to maintain their bodies stable during passive flight, we experimentally examine the effects of bio-inspired bristled disks on their lateral and angular motions during free fall for the Reynolds numbers ranging from O(1) to O(102). The characteristics of disk motions and flow structures are identified for the bristled disks having different numbers of bristles and a circular disk. The comparison between the bristled disks and the circular disk reveals aerodynamic principles underlying the effective stabilization of the bristled disks.

Wrinkling and free-surface breakup by elastic sheet retraction

(Main investigator: Cheolgyun Jung)
Elastic membranes filled with fluids, such as water balloons or capsules, are commonly found in our surroundings and are designed to store and transport fluids effectively. These have a wide range of applications in medical and industrial fields, like being used as a drug delivery system using micro-capsules or as an elastic container for energy transportation, and space robots that protect rovers during landing. Thus, it is essential to understand the potential risks that could lead to their rupture. In this study, we examine the relationship between the retraction of an elastic membrane during rupture and accompanying flow phenomena by adopting a simplified model in which an elastic sheet is initially stretched and floats on the free-surface. Both the shear stress acting on the interface and the wrinkling of the elastic sheet during retraction cause the instability of the free surface and directly affect its breakup into ligaments. By analyzing the multi-physics phenomena quantitatively, we elucidate detailed coupling mechanisms between a retracting elastic sheet and the resulting free-surface flow.

Pattern control of elastic structure based on hydrodynamic coupling

(Main investigator: Seyoung Joung)
Regular wrinkle patterns often arise on the surface-level of thin structures when an internal compression is present. Such patterns which are geometrically characterized with certain wavelengths can be controlled by tailoring the mechanical response of the structure and can be utilized in designing surface structure. By coupling the elastic structure with hydrodynamics, an effective way for pattern control under transient loading is accessible based on the temporal control of wrinkling dynamics. Here, we experimentally investigate the dynamics of a wrinkling elastic loop under transient hydrodynamic loading and find the dynamic conditions for emergence of particular modes.

Break-up of a synthetic capsule immersed in shear flow

(Main investigator: Seyoung Joung)
Synthetic capsules wrap some biological or chemical ingredients using a membrane. They are used in diverse industrial and biomedical applications as mediums of mass transport. When a capsule is immersed in an extreme flow environment, high shear stress exerted on the membrane causes severe deformation and structural failure of the capsule. We experimentally and analytically investigate the dynamics of a synthetic capsule in a simple shear flow and elucidate the underlying mechanism of break-up process.

Dynamic characteristics of sloshing breaking wave generated by single impact wave in low filling condition

(Main investigator: Seongmin Woo)
The sloshing effect refers to the vigorous movement of the liquid’s free surface inside a container in response to the container’s motion. This phenomenon displays highly nonlinear behavior, making its precise definition quite challenging. To gain deeper insights, we conducted the Single Impact Wave experiment, which accurately identified the wave responsible for generating breaking waves. These breaking waves are known to impose significant sloshing loads, especially under low filling conditions. Consequently, we thoroughly investigated the dynamic and flow characteristics of these mesmerizing breaking waves. Moreover, to further enhance our understanding of the sloshing phenomenon, we are integrating Computational Fluid Dynamics (CFD) and AI techniques into our research.

Analysis and modeling of spreading liquid films

(Main investigator: Dong Ju Kim)
Liquid film spreading aided by gravity, jet flow, or surface rotation plays a crucial role in various industries such as semiconductor manufacturing, glass production, cleansing processes, and airfoil icing during flight. Our research focuses on investigating the mesmerizing interplay of surface waves, contact line dynamics, and mass transfer that occur during film spreading. As precision engineering demands increase, these intriguing phenomena is capturing more attention recently. Our team conducts extensive visualizations of liquid film spreading on rotating disks and falling films, diving deep into the physics of solitary waves and partial wetting. To improve efficiency, we are developing low-order numerical models that can compute flow physics much faster than existing 3D CFD models. Furthermore, ongoing studies are centered on the control of spreading film flow.

Mitigation of pressure fluctuation in two-phase slug flow by rib geometry

(Main investigator: Sohyeun Kang)
Slug flow has drawn attention for industrial applications because it is one of the most prevalent and problematic two-phase flows due to severe pressure fluctuations. The effects of rib elements installed at the inner walls of a channel on the flow structure and pressure fluctuations are experimentally investigated with particular focus on how the rib elements alter slugging phenomena as compared with a smooth channel without ribs. For the slug flow in ribbed channels, pressure fluctuations are alleviated because of air bubble entrainment. Two distinct mechanisms of air bubble entrainment are suggested to accounts for different levels of pressure fluctuation mitigation and the increase in flow randomness, which depend on the width-to-height ratio of the rib geometry.

Sloshing flow inside a tank with internal cylindrical structures

(Main investigator: Ki Jong Kim)
Sloshing refers to any motion of a free liquid surface inside a container against external forces exerted on the container. Because of a wide range of industrial applications, numerous researches have been conducted to mitigate the impact by the sloshing flow, using additional internal structures such as baffles. Furthermore, some structures should be mounted inside a container for special purposes such as pump tower, and nuclear power reactor. To better understand how internal components affect the sloshing dynamics, we experimentally investigate water level fluctuation, velocity field, and peak pressure response on tank side walls under several arrangements of cylindrical structures inside the tank.


Formation of capillary waves in liquid film flow

(Main investigator: Dong Ju Kim)
Liquid film flow is observed in numerous industrial applications including biochemical processes, semiconductor manufacturing, engines, and condensers. Capillary waves form in most film flows, and these waves significantly influence heat/mass transport and droplet generation. Therefore, it is desirable to elucidate the statistical characteristics of the capillary waves formed by the liquid film. We experimentally investigate the liquid film flowing on a rotating disk and an inclined plate and also conduct numerical simulations based on low-order modeling to reduce computing cost.

A toroidal bubble rising across a liquid-liquid interface

(Main investigator: Eunseong Moon) doi:10.1017/jfm.2023.457
Bubbles of circular ring shape, namely toroidal bubbles, can be created by releasing a pulsed air jet into the water. We experimentally investigated the vertical penetration of a toroidal bubble through a horizontal liquid–liquid interface. As the toroidal bubble passes through the initial position of the liquid–liquid interface, a great amount of surrounding heavier liquid moves along with it. The volume of the surrounding heavier liquid is up to 50 times the bubble volume, much larger than the transported volume by a bubble of other shapes. Such volume gradually decreases as the toroidal bubble rises. The temporal changes in the liquid volume and ring radius were theoretically analyzed based on the momentum balance. We identified that such temporal changes are induced by forces acting on the surrounding liquid, particularly buoyancy and gravity. The liquid transport throughout the ascending of the toroidal bubble is expected to be applied in various industrial fields to enhance heat and mass transfer between two liquids.

Mitigation of cavitation erosion on a wall with an air pocket

(Main investigator: Changhwan Jang)
Cavitation bubble adjacent to a solid wall induces a bubble jet, which causes a cavitation erosion on a surface of the solid. Recently, an air pocket on a solid surface has been investigated to prevent a cavitation erosion. However, a hydrodynamic loading on a wall with an air pocket still requires further analysis. We numerically study the mitigation of hydrodynamic loading on a walll, and the interaction of an air entrapped in a pocket and a cavitation bubble.

Interaction of a bubble jet with viscoelastic solid

(Main investigator: Jihoo Moon)
Bubble jets are fast liquid jets caused by the asymmetric collapse of gas bubbles. Even a micron-sized bubble can generate a jet with the speed of a few hundred meters per second, exerting a large impulse onto a nearby structure. For this reason, bubble jets have been of great interest in various fields of engineering. Especially in biomedical applications, bubble jets can be utilized for targeted drug delivery. We numerically study the dynamics of a bubble jet interacting with a nearby viscoelastic solid in order to deepen our understanding of bubble collapse which occurs inside a human body.

Cavitation and jet formation in a liquid film

(Main investigator: Ehsan Mahravan) doi:10.1063/5.0060422
Cavitation occurs in a wide range of industrial, chemical, and biological contexts when liquid pressure drops below vapor pressure. The bubble commences to pulsate owing to the pressure difference with the surrounding liquid and undergoes nonspherical collapse if there is any boundary near it, such as a solid surface, a free surface, a particle, or even another pulsating bubble. We consider a bubble within a very thin liquid film. Cavitation in a liquid film occurs in laser-induced forward transfer (LIFT), a method that utilizes microscale cavitation bubbles for nozzle-free printing. Because of the presence of the film, the bubble dynamics are strongly affected by both a free surface and a solid boundary and differ substantially from those near a sole solid boundary.

Underwater explosion near a patterned surface

(Main investigator: Donghyun Kim)
An underwater explosion induces various responses such as shock wave propagation, formation of highly dynamic bubble, inducement of cavitation to surrounding fluid. These violent fluid responses are strongly affect the structural response during explosion process. These phenomena are researched for a long time, however there are issues not described clearly yet. Bubble dynamics related to an underwater explosion and structural responses by the bubble is our main research objective. Structures studied traditionally are usually confined to naval ships or submarines.

Boiling and condensation in a two-phase closed thermosyphon under horizontal vibration

(Main investigator: Sohyeun Kang)
A two-phase closed thermosyphon is a wickless and passive heat transfer device. In the thermosyphon, working fluid vaporizes in the lower evaporator section, and then the vapor condenses in the upper condenser section and returns to the evaporator section by gravitational force. Thermosyphons can be widely used for industrial applications, including heat exchangers, solar collectors, and cooling of electrical devices, batteries, and avionics equipment. These applications, however, may be encountered in diverse dynamic circumstances such as acceleration, rotation, and vibration.  As a first step to make a thermosyphon function properly and improve its heat transfer performance under dynamic conditions, we experimentally investigate boiling patterns of the thermosyphon, when it is subjected to horizontal vibration, by varying the amplitude and frequency of vibration, heat input, and filling ratio. A new parameter which characterizes the intensity of vibration is introduced to determine the effect of horizontal vibration on phase change inside the thermosyphon. When the thermosyphon is subjected to the case of a large vibration-intensity parameter, boiling is suppressed due to the high requirement of superheat. Furthermore, as heat input into the thermosyphon increases, the effects of severe horizontal vibration on boiling suppression are annihilated.

Convective heat transfer of an unsteady jet

(Main investigator: Tong Il Park)
A fluidic oscillator, which generates unsteady sweeping jet without any actuator and moving parts, has received much attention due to its attractive features: high durability to shock and vibration and no electromagnetic interference. We apply the fluidic oscillator to improve the performance of convective heat transfer. The sweeping jet impinges vertically on a heated flat plate. By varying Reynolds number and nozzle-to-plate spacing, we experimentally investigate the characteristics of a heat transfer rate of the plate and examine flow fields to find the flow characteristics responsible for enhancing heat transfer.

Lorentz–force activated oscillating jet

(Main investigator: Jaewuk Jung)
In this study, an oscillating jet activated by Lorentz-force is suggested as an innovative way to deflect jets at an arbitrary frequency and amplitude in conductive fluids. An apparatus consisting of carbon electrodes and permanent NeFeB magnets surrounding the nozzle end is devised so that a lateral Lorentz force generates a crossflow that deflects the fluid jet. Trajectories and flow structures of vectored and oscillating jets as electromagnetic and fluid variables changes are investigated. We expect the new method to be beneficial in enhanced mixing and flow control in liquid metal cooling and marine applications.

Prediction of hydrodynamic pressure using deep learning in sloshing flow

(Main investigator: Ki Jong Kim)
Sloshing flow in fluid dynamics which refers to the movement of liquid back and forth inside a container due to external force. In terms of the prediction of slosh-induced pressure, deep learning (DL) is emerging as a powerful tool for predicting the pressure field using an accumulated database of the measured pressure and image recognition by flow visualization. We explore the prediction of slosh-induced pressure using image-based DL for various pressures such as regular, random, impulse, and peak pressure with a single algorithm. This study is valuable in that the dynamic characteristics using DL can be predicted from the wave image, which indicates the kinematic source.

Ocean wave pattern and wave power generation efficiency through vertical cylinder arrays

(Main investigator: Dong Hyup Youn)
Ocean structures, such as offshore wind turbines and bridges, experience phenomena in which waves interact with their supports, leading to effects like wave run-up or wave breaking. Additionally, the presence of these structures alters wave behavior through refraction, diffraction, scattering, reflection, and superposition, resulting in complex and unpredictable patterns, especially when multiple structures are present. To investigate these phenomena, we are conducting scaled-down experiments. We arrange cylindrical structures and observe the interactions between the cylinders and the surrounding waves to understand the effects of cylinder size, gap, and wavelength relationships on the amplification of wave heights through superposition. This amplification of wave heights through superposition can focus wave energy conversion efficiency, leading to increased effectiveness in wave power generation. Furthermore, we are also researching to verify the efficiency enhancement through scaled-down wave power generators.

Reinforcement learning-based optimization for the shape and valve position of a scroll compressor

(Main investigator: Janggon Yoo)
The scroll compressor, employed in large-capacity refrigeration cycles, functions by orbiting two scroll profiles to compress the refrigerant. Designing the scroll compressor is essential to enhance the energy efficiency, compression capacity, and discharge pressure. However, optimizing the compressor’s component positioning and shape is challenging because of complicated nonlinear boundary conditions. The optimization problem is solved using reinforcement learning utilizing an automatic scroll design algorithm and a low-order scroll compressor thermal analysis model. A novel technique involving multiple steps and degrees of freedom was proposed to optimize the position and number of discharge valves and the shape of the scroll compressor. The optimization method can be applied to the commercial scroll compressor design process.

Instability patterns of particles by the overpressure

(Main investigator: Jaehun Yoo)
Packed particles show certain instabilities when the pressure is induced and such instability forms specific patterns over time. We are conducting research to identify the factors that determine the formation of these patterns. This research can be applied in the field of fire safety and defense industry.

Liquid CO2 spray cooling for LNG tanks

(Main investigator: Siyoung Park, Hyeeun Shim)
“Cooling down” is an essential prelude to loading cryogenic LNG, necessitating the chilling of cargo tanks and conduits. The process involves the introduction of liquefied carbon dioxide (LCO2) via spray nozzles into each cargo tank. The transition from ambient temperature (post-gassing up) to a predetermined temperature constitutes the “initial cool down” phase, distinguishable from routine cooling during ballast voyages. Prior to the infusion of LNG into an LNG vessel’s cargo system, including the cargo tanks, requisite cooling to approximate LNG temperature is mandatory. Mitigating the cargo tank temperature curtails the heat reservoir available for transfer to and subsequent warming of the incoming LNG. This deliberate cooling curbs vapor generation within reasonable thresholds. To evaluate the efficacy of the LCO2 spray cool-down process and comprehend phase transition dynamics, computational fluid dynamics (CFD) simulations are employed. Subsequently, the study offers insights into optimal design parameters and operational conditions, culminating in recommendations for facilitating optimal states in the LNG cargo tank.

Potassium Heat Pipe for Small Modular Reactors (SMRs)

(Main investigator: Sohyeun Kang)
Heat pipes have garnered renewed attention in contemporary times, emerging as focal points of rigorous investigation within domains such as nuclear engineering and space exploration. Technological advancements, exemplified by the advent of Small Modular Reactors (SMRs), have garnered substantial interest due to their capacity to effectively address the escalating energy requisites. These reactors possess the capability to produce power in close proximity to densely populated regions, accommodating heightened energy consumption without necessitating extensive spatial occupancy or protracted construction periods. In this context, the deployment of SMRs mandates the integration of a space-efficient heat dissipation system, a criterion well-suited for realization through the utilization of heat pipes. This study endeavors to elucidate the meticulous design of heat pipes tailored for SMRs, employing a synergy of theoretical models and Computational Fluid Dynamics (CFD) simulations. This framework buttresses the subsequent research phase, wherein a prototypical implementation of the heat pipe within the SMR infrastructure is established, ensuring unwavering operational stability and requisite heat transfer efficiency.

Control of droplet scattering behavior in the process of spin coating/developing

(Main investigator: Dong Ju Kim)
Spin coating/developing constitutes a critical process in semiconductor manufacturing. Precisely spreading chemically sensitive liquids onto a rapidly rotating wafer is imperative for optimal results. Unfortunately, the presence of scattered droplets due to various factors poses a risk of wafer contamination and performance degradation. To address this challenge, our research involves high-speed imaging of droplets during this process and the development of reliable quantitative models to predict their behavior. By doing so, we aim to enhance the precision and efficiency of spin coating/developing, ensuring superior semiconductor production outcomes.

Design of sphere to suppress vortex-induced vibration

(Main investigator: Minseop Lee)
The sphere connected to the elastic cable (Drogue system) can be utilized in many areas of the industry. When the drogue system interacts with the uniform flow, the sphere oscillates from side to side under certain conditions (Vortex-induced vibration). Since such strong vibration is a negative factor from the point of view of industrial applications, it is necessary to design a stable drogue system. We present a design that adds a spiral-shaped pattern to the surface of a sphere that breaks the vortex structure, and the vibration of the drogue system is significantly reduced.

Flow-induced vibration of a hydroturbine

Flow-induced and acoustic-induced vibration of a pipe

Fluid-structure interaction of oil spill prevention technology

Oil separation of a compressor

Thin film flow on a rotating disc

Fluid mixing inside a reactor chamber 

Open-loop wind tunnel

Horizontal circulation water tunnel

Free-surface water tunnel

Large-scale water tank

Operated by the department

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