• Original Article

    A SIMULATION OF MOBILE BED BEHAVIOR BY USING SOLID MPS METHOD

    고체입자를 적용한 입자법을 이용한 해저면 운동 연구

    K.S. Kim

    김경성

    Large waves induce intense impact loads on the seabed. This phenomenon has been investigated through theoretical, experimental, and numerical approaches by several … + READ MORE
    Large waves induce intense impact loads on the seabed. This phenomenon has been investigated through theoretical, experimental, and numerical approaches by several researchers. In this study, the Moving Particle Semi-implicit(MPS) method was employed to simulate the behavior of a mobile seabed under large waves, such as those generated by tsunamis. To accurately simulate solid particle interactions, newly developed particle interaction models were implemented and validated against corresponding experimental data. The numerical results showed good agreement with experimental findings. Additionally, particle velocity and pressure were plotted numerically, demonstrating the physical phenomena of mobile bed behavior under wave impact. - COLLAPSE
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    31 December 2024

  • Original Article

    COMPUTATIONAL ANALYSIS OF AERODYNAMICS AND STATIC STABILITY OF RE-ENTRY VEHICLE AT LOW ALTITUDES

    재진입 비행체의 저고도에서의 공력 및 정적 안정성에 관한 전산해석

    B.G. Park, S.J. Jo, S.M. Choi, S.J. Hwang, R.S. Myong

    박보근, 조성진, 최수민, 황선재, 명노신

    Re-entry vehicles may experience unstable flow during descent to Earth at low altitudes and the flow can negatively affect the stability of … + READ MORE
    Re-entry vehicles may experience unstable flow during descent to Earth at low altitudes and the flow can negatively affect the stability of the vehicle. In this study, we investigate the characteristics of rear wake flow and frontal shock waves of re-entry vehicles for the angle of attack of 0º to -60º in low altitude transitional regime using a Navier-Stokes code. Five species and the transition SST turbulence model are used to describe the low-altitude flows at subsonic to hypersonic speed. It was shown that recirculation rings are getting bigger at lower altitudes and smaller with increasing angle of attack. By calculating the pitching moment at the center of gravity, the vehicle was shown to be statically stable at a low angle of attack. The angle of attack of neutral static stability decreases as the Mach number increases. Additionally, the aerodynamic center of the vehicle is calculated at each altitude and moves near the vehicle as the Mach number increases. - COLLAPSE
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    31 December 2024

  • Original Article

    NUMERICAL INVESTIGATION OF PROPELLER WAKE EFFECT ON THE WING AERODYNAMICS OF AIRCRAFT WITH DISTRIBUTED ELECTRIC PROPULSION

    프로펠러 후류 효과가 분산전기추진 항공기의 날개 공력 특성에 미치는 영향에 대한 전산해석

    H.S. Song, Y.H. Hwang, S.J. Kim, R.S. Myong, H. Lee

    송현수, 황유현, 김시진, 명노신, 이학진

    The development of eco-friendly aircraft with a distributed electric propulsion(DEP) system has garnered significant attention due to the push for carbon neutrality. … + READ MORE
    The development of eco-friendly aircraft with a distributed electric propulsion(DEP) system has garnered significant attention due to the push for carbon neutrality. The DEP system helps improve aerodynamic efficiency, reduce noise levels, and lower carbon emissions. However, as the number of propellers increases, the interaction between the propellers and wings has emerged as a critical factor affecting aerodynamic performance. This study delves into the effects of propeller wakes on flow separation, skin friction, and overall aerodynamic performance of fixed-wing aircraft in detail. Using the lattice- Boltzmann method(LBM), computational analysis of the NASA X-57 Maxwell aircraft in its full configuration with 12 propellers was conducted. The study concluded that the propeller wake accelerates the flow around the fixed-wing, leading to an increase in suction peak and skin friction, as well as a delay in flow separation. Additionally, it was confirmed that the strong upwash flow induced by counter-rotating propellers results in flow separation at high angles of attack, thereby increasing drag. - COLLAPSE
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    31 December 2024

  • Original Article

    NUMERICAL INVESTIGATION ON INCREASING COOLING EFFICIENCY FOR LI-ION BATTERY IN ELECTRIC VEHICLE

    전기차용 리튬 이온 배터리의 냉각 효율 제고에 관한 전산해석적 연구

    J.W. Kim

    김재원

    Numerical investigation has been performed for the cooling efficiency of Lithium ion battery adopted in electric vehicles. Temperature of Li-ion cell should … + READ MORE
    Numerical investigation has been performed for the cooling efficiency of Lithium ion battery adopted in electric vehicles. Temperature of Li-ion cell should be controlled under rigorously restricted range for both the very safe from thermal runaway and normal driving of the electric vehicles. The electric cell is heat source during charging and discharging process of it and its temperature could increase up to the pre-assigned limits without proper cooling devices. The present work is looking for efficient cooling system for Li-ion battery which is large heat source for its operation in EV. Several cooling models are proposed to this research and its performance is revealed for each system. Five cooling models and the reference model from prior work are numerically examined for temperature control of the present Li-ion battery. The present investigation has been carried out with normal driving conditions of electric vehicles presented in market. Consequently, the model with improved outlet geometry shows enhanced cooling performance relative to other suggestions including the reference model which has been adopted in running EVs. - COLLAPSE
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    31 December 2024

  • Original Article

    EFFECTS OF TURBULENCE MODELS ON FLOWS AROUND A AIRFOIL WITH A ROTATING CYLINDER

    익형 앞전에 위치한 회전 실린더 형상의 유동 해석 및 난류 모델 비교

    S.H. Jang, S.J. Bae, Baddegamage B.H.B.P.D., J.Y. Kim, M. Yoon

    장승현, 배성종, B.H.B.P.D.Baddegamage, 김준영, 윤민

    The influences of turbulence models on the aerodynamic performance of a rotating airfoil are analyzed. An airfoil equipped with a rotating cylinder … + READ MORE
    The influences of turbulence models on the aerodynamic performance of a rotating airfoil are analyzed. An airfoil equipped with a rotating cylinder at its leading edge generates additional lift due to the Magnus effect. Numerical simulations are performed at a Reynolds number of 46,200 using six different turbulence models: standard k-epsilon, realizable k-epsilon with enhanced wall treatment(EWT), k-omega, shear stress transport, Spalart―Allmaras, and k-kl-omega. The realizable k-epsilon with EWT model shows the closest agreement with experimental data, with an error rate below 5%. This model accurately predicts the wake regions of the airfoil and the low-pressure regions around the rotating cylinder, leading to a higher lift coefficient than those predicted by other models. The present study highlights the importance of turbulence model in predicting complex flow phenomena and contributes to the foundation for future design and performance optimization of engineering applications utilizing the Magnus effect. - COLLAPSE
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    31 December 2024

  • Original Article

    NUMERICAL STUDY OF TIP LEAKAGE VORTEX REDUCTION FOR A PUMPJET PROPULSOR

    펌프젯 추진기 날개 끝 누설 와류 감소를 위한 수치해석 연구

    J.I. Kim, I.R. Park, H.S. Seol, H.S. Jung

    김제인, 박일룡, 설한신, 정홍석

    This study presents the results of a numerical analysis using the Reynolds-Averaged Navier-Stokes (RANS) method to investigate the potential mitigation of tip … + READ MORE
    This study presents the results of a numerical analysis using the Reynolds-Averaged Navier-Stokes (RANS) method to investigate the potential mitigation of tip leakage vortex (TLV) in the KRISO pumpjet propulsor through rotor tip shape modifications. Three alternative tip geometries were designed by extending the rotor tip toward either the pressure side, the suction side, or both. The present comparative analysis revealed that the pressure-side extension (PSE) tip achieved the most significant reduction in TLV compared to the original design. A detailed flow analysis in the gap indicated that the PSE tip effectively reduced both the pressure drop and velocity magnitude within the gap. However, the effect of the PSE tip on the overall efficiency of the pumpjet propulsor was found to be negligible. - COLLAPSE
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    31 December 2024

  • Original Article

    ANALYSIS OF AERODYNAMIC INTERACTION DUE TO INTERFERENCE EFFECTS BETWEEN ROTOR, GROUND AND OBSTACLE

    로터와 지면 및 장애물의 간섭 효과에 의한 공기역학적 특성 분석

    D. Kim, Y. Jo

    김도현, 조영민

    Rotorcraft operating in urban environments can encounter aerodynamic instability caused by interference effects from the ground and obstacles. This study investigates these … + READ MORE
    Rotorcraft operating in urban environments can encounter aerodynamic instability caused by interference effects from the ground and obstacles. This study investigates these issues using computational fluid dynamics (CFD). Five comparative cases were analyzed, based on experimental cases involving scaled rotors and obstacles. The effects of obstacle presence and variations in distances between the ground, obstacles, and rotors were examined. The results revealed a sharp increase in rotor thrust due to ground effect and flow recirculation caused by back-flow. Such phenomena are expected to significantly reduce flight stability and reliability, posing substantial challenges to the operation of rotorcraft in urban areas. - COLLAPSE
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    31 December 2024

  • Original Article

    EFFECT OF GRIDS ON VEHICLE AERODYNAMICS SIMULATIONS UNDER SIDE WIND CONDITIONS

    횡풍 조건에서 격자가 차량 공기역학 시뮬레이션에 미치는 영향

    J.H. Son, M.H. Baek, S.H. Yoon, D.H. Shin

    손주훈, 백민하, 윤승현, 신동혁

    This study analyzes the aerodynamic characteristics of a vehicle under side wind conditions using Computational Fluid Dynamics. A DrivAer fastback model, based … + READ MORE
    This study analyzes the aerodynamic characteristics of a vehicle under side wind conditions using Computational Fluid Dynamics. A DrivAer fastback model, based on a realistic vehicle design, was utilized, and multi-block mesh refinement techniques were applied in a grid study. The initial grid study began with a headwind condition, leading to the identification of optimal grids. These configurations were then used to measure drag and lift coefficients under side wind conditions which were compared with experimental data. The study revealed that the grid refinement significantly impacts the accuracy of the results. Generally, the accuracy improves with increasing the number of grid points. With a multi-block refinement technique, an optimized grid with a significantly lower number of grid points compared to the best accuracy-producing grid, still produced similar accuracy: errors in drag/lift coefficients on the best accuracy-producing grid are 2.6% and 15.8%, while those are 2.8% and 21.9% on an optimized grid. The result indicates that achieving efficient simulations is possible by appropriately adjusting the number of grids, thereby reducing computational costs. This study suggests that appropriate multi-block mesh refinement techniques can lead to high-efficiency simulations while maintaining precision, crucial for enhancing aerodynamic analysis and improving vehicle design across diverse wind conditions. - COLLAPSE
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    31 December 2024

  • Original Article

    STUDY ON BOUNDARY CONDITIONS FOR CFD/FREE WAKE COUPLED HYBRID METHOD

    CFD/자유 후류 모델을 결합한 하이브리드 기법의 원방 경계 조건 연구

    D. Park, M.H. Cho, S.H. Park

    박다운, 조민형, 박수형

    In the aerodynamic analysis of rotors, low-fidelity BEM-wake modeling methods have limited accuracy, while high-fidelity Computational Fluid Dynamics(CFD) poses significant computational challenges. … + READ MORE
    In the aerodynamic analysis of rotors, low-fidelity BEM-wake modeling methods have limited accuracy, while high-fidelity Computational Fluid Dynamics(CFD) poses significant computational challenges. To address these limitations, a hybrid method combining CFD with a free-wake model has been developed. This employs CFD in the vicinity of the rotor blades and the free-wake model for the far-field wake. The specification of CFD boundary conditions at the coupling interface is critical. Therefore, this study investigates suitable boundary conditions for hybrid methods in rotor problems. Each of boundary condition is based on the Bernoulli equation and the specified constant total enthalpy. It is demonstrated that using boundary condition the based on constant total enthalpy provides more accurate aerodynamic analysis results over a wider range of flight speed compared to it based on the Bernoulli equation. - COLLAPSE
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    31 December 2024

  • Original Article

    COMPUTATIONAL SIMULATION OF TURBULENT FLOW USING AN IMPROVED PANS MODEL AT HIGH REYNOLDS NUMBERS: ROTATING CYLINDER WITH A FIXED SPIN RATIO

    개선된 PANS 난류 모델 기반 높은 레이놀즈수 난류 유동 수치 모사: 회전율이 고정된 회전실린더

    H.J. Kim, W. Seok, S.B. Lee

    김효주, 석우찬, 이상봉

    Flow around a rotating cylinder was analyzed using an improved Partially Averaged Navier-Stokes(PANS) model within a Reynolds number(Re) range of 104 … + READ MORE
    Flow around a rotating cylinder was analyzed using an improved Partially Averaged Navier-Stokes(PANS) model within a Reynolds number(Re) range of 104 to 106. To observe the flow characteristics of the rotating cylinder over a wide range of Reynolds numbers, the rotation rate, which represents the ratio of rotational flow to free flow, was fixed at 1. Compared to the fixed cylinder where a sharp drop in the drag coefficient is observed, the rotating cylinder showed a monotonic decrease in both drag and lift coefficients as the Reynolds number increased on a logarithmic scale. With the application of counter-clockwise rotation, the upper surface of the cylinder experienced a local deceleration flow due to the flow opposing the free stream. This caused the separation point to move upstream compared to that of the fixed cylinder, directing the flow relatively outward from the cylinder. Conversely, on the lower surface of the cylinder, an additional flow in the same direction as the free stream resulted in partial acceleration, delaying the separation point further downstream and causing the flow to converge inward toward the cylinder. With increasing Re, the separation point on the lower surface remained nearly constant, whereas that on the upper surface gradually moved downstream, with the flow direction increasingly converging inward. Therefore, the vortices formed directly behind the cylinder transitioned from asymmetric flow to a nearly symmetric flow pattern. However, further downstream, deflection is still observed despite the increase in Re. - COLLAPSE
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    31 December 2024

  • Original Article

    A STUDY ON FLOW COEFFICIENT AND FLOW INDUCED FORCE FOR GLOBE VALVE

    전산유체역학 해석을 이용한 글로브밸브의 유량계수와 유동힘에 대한 연구

    J. Kim, S. Lee, J.H. Lee

    김재형, 이상혁, 이정희

    Recently, as the performance of valves changes and deteriorates depending on operating conditions and operating environment, the valve used in industrial plants … + READ MORE
    Recently, as the performance of valves changes and deteriorates depending on operating conditions and operating environment, the valve used in industrial plants such as nuclear power plant diagnosis through real-time monitoring is required. The valves must undergo functional qualification. A test-based methodology is needed when performing verification of the remaining similar valves using the qualification results of the representative valve. In this study, computational fluid dynamics analysis was used to calculate the force transmitted to the valve plug by considering the actual situation where the stroke speed changes using the flow coefficient and pressure ratio. Using this, an analysis method was presented to calculate the force added to the valve under high-temperature and high-pressure operating conditions where experiments are impossible. The results of this study can be used as a test-based methodology applicable to new valve qualification standards. - COLLAPSE
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    31 December 2024

  • Original Article

    NUMERICAL STUDY ON INVERSE EXTRUSION FOR EXTRUDING MULTI-LUMEN TUBE

    멀티루멘 카테터 압출을 위한 역압출 수치 해석에 관한 연구

    W. Jun, W. Kim, E. Lee

    전원진, 김우진, 이은택

    This study addresses the challenges in die design for extruding multi-lumen tubes, which have small diameters and complex cross-sectional geometries. We present … + READ MORE
    This study addresses the challenges in die design for extruding multi-lumen tubes, which have small diameters and complex cross-sectional geometries. We present a method to utilize inverse extrusion simulation for designing extrusion dies specifically adapted to the intricate geometries. Specifically, the target geometry consists of one main and three sub lumens. Practical extrusion conditions with drawing are applied as boundary conditions in the simulation. The die geometry is designed through inverse extrusion simulation and subsequently validated via direct extrusion simulation. The predicted extrudate is well matched to the target geometry. The inverse extrusion simulation is the powerful and effective method to design extrusion dies for multi-lumen tubes with complex cross- sectional geometries. - COLLAPSE
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    31 December 2024

  • Original Article

    NUMERICAL STUDY ON HEAT TRANSFER CHARACTERISTICS OF PERMANENT MAGNET SYNCHRONOUS MOTOR UNDER VARIOUS OPERATING CONDITIONS

    구동 조건에 따른 영구자석 동기 전동기의 열전달 특성에 관한 수치적 연구

    J. Kwon, G. Son

    권재범, 손기헌

    This study focuses on the thermal generation and heat transfer characteristics of a permanent magnet synchronous motor(PMSM) which is considered as an … + READ MORE
    This study focuses on the thermal generation and heat transfer characteristics of a permanent magnet synchronous motor(PMSM) which is considered as an alternative to traditional low-efficiency induction motor(IM) in HVAC applications. Three-dimensional computations are conducted to analyze the flow and heat transfer characteristics of the PMSM. The effect of operating conditions, such as the load and the rotational speed of the PMSM, on the heat transfer characteristics are investigated numerically. As the load torque decreases, the heat transfer ratio from the rotor to the air gap increases, while the ratio to the shaft decreases. As the rotational speed decreases, the heat transfer ratio from the rotor to the air gap decreases, while the ratio to the shaft increases. Based on temperature rise results and heat generation data, predictive equations for the temperature rise of rotor and stator components are derived. - COLLAPSE
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    31 December 2024

  • Original Article

    EVALUATION OF THE EFFECTS OF WATER DEPTH AND WIDTH ON THE RESISTANCE PERFORMANCE OF HIGH-SPEED VESSELS THROUGH COMPUTATIONAL SIMULATION IN A HIGH-SPEED TOWING TANK

    고속예인수조의 수치 모사를 통한 수심 및 폭이 고속선의 저항 성능에 미치는 영향 평가

    J.S. Park, H.J. Kim, M. Lee, S.B. Lee

    박준상, 김효주, 이무열, 이상봉

    Computational simulations were conducted to examine the resistance changes acting on a high-speed planing vessel as the size of the towing tank … + READ MORE
    Computational simulations were conducted to examine the resistance changes acting on a high-speed planing vessel as the size of the towing tank was varied. The vessel model used was a mono-hull planing vessel. The width of the computational domain ranged from 8 meters(4 meters per half-width), the actual width of the high-speed towing tank, up to a maximum of 29.16 meters(14.58 meters per half-width). The depth was varied from the actual depth of 5.5 meters up to a maximum of 14.58 meters. When the depth was 5.5 meters, resistance increased by more than 2% as the width increased, and then converged at an increase of approximately 1.5%. This trend remained similar until the depth reached 8.5 meters. However, when the depth exceeded 11 meters, the total resistance change due to the increase in width nearly disappeared. When the width was 4 meters, the total resistance showed little change due to depth, but when the width was 6 meters, the resistance variation due to depth increased up to 2.3%, converging at depths greater than 11 meters. - COLLAPSE
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    31 December 2024

  • Original Article

    COMPARISON OF PARALLELIZATION PERFORMANCE OF FIRE DYNAMIC SIMULATOR(FDS) PROGRAM

    화재모사(FDS) 프로그램의 병렬화 성능 비교

    J.R. Shin, D.H. Kim, T.W. Kim

    신재렬, 김동현, 김태우

    Fire simulation is a difficult engineering problem due to numerous physics-chemical processes, but NIST(National Institute of Standards and Technology)’s Fire Dynamics Simulator … + READ MORE
    Fire simulation is a difficult engineering problem due to numerous physics-chemical processes, but NIST(National Institute of Standards and Technology)’s Fire Dynamics Simulator (FDS) has been widely used for validation of physical models about fire simulation and practical fire problems by using a variety of physical models. However, there is no clear guideline about the optimal parallel performance for the MPI libraries and compilers, except the FDS parallel performance portion of the user guide. In this study, the parallel performance of two MPI libraries (Open MPI, Intel MPI) for FDS were evaluated with a 3D heat transfer problem. Looking at the results, the Intel MPI with Intel compiler showed 38 % faster performance than the Open MPI with GNU compiler. In two MPI libraries, an OpenMP using threading had little impact on parallel performance. - COLLAPSE
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    31 December 2024

  • Original Article

    NUMERICAL SIMULATION ON THE SMOOTHED PARTICLES OF LIQUID DROPLETS AGAINST AN EXPLOSION SCENARIO FOR A MOLTEN SALT REACTOR

    용융염 원자로의 폭발 시나리오에 대비한 액적의 완화 입자 수치 모사

    H.T. Kim, S.I. Kim, S.M. Chang

    김형태, 김성일, 장세명

    In this study, an MSR(Molten Salt Reactor) of the micro-scale, which is defined as the portable size of a military truck, acts … + READ MORE
    In this study, an MSR(Molten Salt Reactor) of the micro-scale, which is defined as the portable size of a military truck, acts under the assumptive scenario of a missile attack to make a cylindrical hole through the steel container covering the reactor fuel. 50 kg of TNT explodes to induce a blast wave with high-speed jet flow. FEM and SPH(smoothed particle hydrodynamics) method is modeled for the present problem, and with this numerical method, the precise time-dependent solutions are visualized for the 45-degree case as well as the vertical penetration. The Sedov theory(1959) also gives the physical interpretation of the computational result, providing the feasibility of predictive correlation on the radius of damage and action. - COLLAPSE
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    31 December 2024

  • Original Article

    ANALYSIS OF AXISYMMETRIC BASE FLOWS WITH COMPRESSIBILITY AND ROTATION/CURVATURE CORRECTIONS TO TURBULENCE MODEL

    난류모델 압축성 및 회전/곡률 보정을 적용한 축대칭 기저유동 해석

    J. Park, D.H. Kim, S. Lee, J.S. Park

    박재형, 김동현, 이승수, 박진석

    This paper presents the results of two RANS model corrections, compressiblity correction and rotation/curvature correction to k - ω SST model for … + READ MORE
    This paper presents the results of two RANS model corrections, compressiblity correction and rotation/curvature correction to k - ω SST model for base drag prediction. The performance of the corrections for axisymmetric base flow simulations is scrutinized by comparing the detail flow features, such as velocity profile, turbulent kinetic energy profile and Reynolds shear stress. It is found that two corrections improve the prediction accuracy of base drag when compared to the baseline model. - COLLAPSE
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    31 December 2024

  • Original Article

    COMPARISON OF 2D FLOW ANALYSIS BETWEEN PINN AND COMMERCIAL SOFTWARE

    PINN과 상용 소프트웨어의 2차원 유동해석 비교

    H.J. Lee, W.T. Jung, J.H. Jung

    이호준, 정웅태, 정재호

    This paper evaluates the potential of Physics-Informed Neural Networks(PINN) for addressing Computational Fluid Dynamics(CFD) problems. Flow analysis based on the Navier-Stokes equations … + READ MORE
    This paper evaluates the potential of Physics-Informed Neural Networks(PINN) for addressing Computational Fluid Dynamics(CFD) problems. Flow analysis based on the Navier-Stokes equations was conducted using PINN, and the results were compared with those from the commercial software ANSYS Fluent. The study results show that while PINN provides relatively accurate solutions, it requires more computational time compared to commercial software. Furthermore , when comparing results based on the same number of collocation points and mesh nodes, the commercial software demonstrates higher accuracy. Moreover, ANSYS Fluent with 5,000 mesh nodes shows less error than PINN with 50,000 collocation points. In conclusion, although PINN is currently insufficient to replace commercial software in fluid flow analysis, further technological advancements are necessary to enhance its performance. - COLLAPSE
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    31 December 2024

  • Original Article

    DEVELOPMENT AND VALIDATION OF A FLOW SOLVER BASED ON THE ENTROPIC LATTICE BOLTZMANN METHOD

    엔트로피 격자 볼츠만 기법을 기반으로 한 유동해석 코드 개발 및 검증

    J. Kim, Y. Jo

    김준재, 조영민

    The lattice Boltzmann method(LBM) has been widely used to model fluid dynamics by reproducing the Navier-Stokes equations, and successfully handling complex phenomena … + READ MORE
    The lattice Boltzmann method(LBM) has been widely used to model fluid dynamics by reproducing the Navier-Stokes equations, and successfully handling complex phenomena such as multi-phase, multi-component, and microscale flows. Despite its versatility, the standard LBM faces significant limitations when applied to high Mach number and low-viscosity flows, where numerical inaccuracies become prominent. To overcome these challenges, Karlin et al.[Europhys. Lett., 47, pp. 182–188(1999)] introduced the entropic lattice Boltzmann method(ELBM), a significant advancement that employs Boltzmann’s H-theorem and the maximum entropy principle(MEP) to ensure compliance with the second law of thermodynamics, which is often violated by the standard LBM. In this study, we present the development and validation of a flow solver based on the ELBM, implemented with GPU parallel computing. The solver’s performance is demonstrated through simulations of flow over a 2D circular cylinder and the NACA0012 airfoil, validating its accuracy. - COLLAPSE
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    31 December 2024

  • Original Article

    NUMERICAL INVESTIGATION OF CONTACT ANGLE EFFECT ON OIL-WATER SEPARATION FLOW PASSING THROUGH A POROUS STRUCTURE

    접촉각에 따른 다공성 구조물을 통과하는 기름-물 유동의 유수분리 영향 연구

    T. Ha, I. Yoon, S. Shin

    하태진, 윤익로, 신승원

    The primary objective of this study is to analyze the movement of the oil-water contact line and its effect on oil-water separation … + READ MORE
    The primary objective of this study is to analyze the movement of the oil-water contact line and its effect on oil-water separation under various external pressure gradients, surface properties, and cylinder spacing. Capital a two-dimensional numerical simulation based on the Level Contour Reconstruction Method(LCRM) was conducted to investigate the two-phase(oil-water) flow through the gaps between cylinders representing mesh geometry for oil-water separation filter. The study considered a range of external pressure gradients(0–1000 kPa/m) and cylinder spacings(100–1000 µm), with a focus on comparing two extreme surface conditions of hydrophilicity and hydrophobicity. The results demonstrate that variations in contact angle and cylinder spacing significantly influence oil-water separation efficiency. Hydrophilic surfaces maintained a stable contact line and resisted oil penetration even under increased external pressure gradient, whereas hydrophobic surfaces exhibited rapid oil infiltration due to the ease of contact line displacement. Notably, in a specific range of cylinder spacing(300 µm < d < 600 µm), hydrophilic surfaces sustained a stable separation state at much higher pressure gradient compared to hydrophobic surfaces. - COLLAPSE
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    31 December 2024

  • Original Article

    A COMPUTATIONAL FLUID DYNAMICS-BASED THERMAL MANAGEMENT MODEL IN BATTERY SWAPPING STATION

    배터리 교환형 충전소의 전산유체역학기반 열관리 모형

    E.Y. Yang, Y. Lee, S. Choi

    양은용, 이용권, 최상헌

    The demand for electric mobility is rising, but the time it takes to charge batteries remains a concern for users. Rather than … + READ MORE
    The demand for electric mobility is rising, but the time it takes to charge batteries remains a concern for users. Rather than reducing the battery charging cost, battery swapping stations(BSS) offer an alternative solution by allowing users to exchange a discharged battery for a fully charged one. For the purpose of thermal management, we develop a computational fluid dynamics(CFD) model, which describe thermal behavior and airflow within the BSS. Heat generation in the batteries was modeled considering Joule heating, and the pressure minor loss at the outlet was estimated using a separate model that provides the same pressure drop due to the fans. The model accuracy was validated with experimental data measured in high-temperature and low-temperature batteries. As a result, in both high- and low- temperature batteries, temporal variations of the CFD model were consistent with experimental results. The proposed CFD model has the potential to provide guidance for improving designs and operating conditions of the BSS, ultimately enhancing thermal management efficiency. - COLLAPSE
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    31 December 2024

  • Original Article

    A STUDY ON THE EFFECT OF THE VOF SCHEME ON NUMERICAL DIFFUSION IN THE COMPUTATIONAL SIMULATION AROUND A HIGH-SPEED VESSEL

    고속선 주위 유동 해석에서 VOF의 차분 기법이 수치 확산에 미치는 영향에 관한 연구

    M.G. Sim, M. Lee, S.B. Lee

    심민경, 이무열, 이상봉

    Computational simulations around a mono-hull planing vessel were performed to investigate the effects of time step size and the accuracy of VOF … + READ MORE
    Computational simulations around a mono-hull planing vessel were performed to investigate the effects of time step size and the accuracy of VOF scheme on the numerical diffusion of phase interface. By evaluating the convergence index for the time step size, it was shown that increasing the time step size results in numerical diffusion, which in turn can impact the accuracy of the computational solution. To systematically assess the effects of the numerical diffusion, simulations were conducted across various flow speeds and time step sizes. The results revealed that numerical diffusion at the free surface interface leads to changes in viscosity and density, which subsequently influence the total resistance acting on the hull. The accuracy of the difference schemes for the VOF variable was analyzed based on the interpolation between first-order upwind and higher-order schemes, determined by setting the upper and lower limits for the Courant number(Co), respectively. - COLLAPSE
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    31 December 2024

  • Original Article

    COMPRESSIBLE FLOW ANALYSES OF WING MODELS AND COMPARISON WITH EXPERIMENT USING LATTICE BOLTZMANN METHOD

    Lattice Boltzmann Method를 활용한 3차원 날개의 압축성 유동해석 및 풍동시험 결과 비교

    H.J. Kim, D.H. Kim

    김현진, 김동현

    In this study, aerodynamic analyses for several wind-tunnel test models in compressible flow were validated using the lattice Boltzmann method(LBM), and the … + READ MORE
    In this study, aerodynamic analyses for several wind-tunnel test models in compressible flow were validated using the lattice Boltzmann method(LBM), and the numerical results were compared with experimental data. The primary objective of this study is to evaluate the numerical accuracy and potential limitations of a meshless, particle-based methodology implemented in XFlow software, which features an efficient octree mesh generator capable of handling complex geometries with ease. It is demonstrated that achieving reasonable numerical results by using LBM requires a critical particle resolution level. However, the greatest challenge in practical computational fluid dynamics(CFD) analysis using LBM is determining the appropriate number of particles needed to obtain reliable results. To address this, inviscid and viscous flow analyses for several experimental wing models were conducted using different Element Resolution Ratios(ERR). The findings presented in this paper provide valuable insights into determining the appropriate level of ERR for accurate flow analysis of three-dimensional wing shapes using LBM. - COLLAPSE
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    31 December 2024
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