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Original Article
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HIGH-FIDELITY LBM ANALYSIS OF INTERNAL FLOW STRUCTURES IN AN EXHAUST STACK SYSTEM WITH VARYING NUMBERS OF ACOUSTIC BAFFLES
소음 저감용 배플 개수 변화에 따른 배기 스택 시스템 내부 유동 특성에 관한 고정밀도 LBM 해석
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D. Jeong, K.T. Park, C.J. Hong, J.S. Han, H.S. Yang, J.B. Kim, K.H. Moon, H. Lee
정도윤, 박규태, 홍창진, 한종섭, 양희수, 김종범, 문근환, 이학진
- This study investigates the internal flow characteristics of an industrial exhaust stack as a preliminary step toward mitigating noise emissions from power …
- This study investigates the internal flow characteristics of an industrial exhaust stack as a preliminary step toward mitigating noise emissions from power generation and manufacturing facilities in urban environments. While previous research on silencer design has explored various flow-modifying devices, including baffles, vanes, and honeycomb structures, this work focuses on the aerodynamic effects of baffle number within the stack. Two configurations with different baffle counts, denoted B9 and B17, were examined to evaluate their influence on internal flow development, outlet flow propagation, and external dispersion behavior. In this study, very large eddy simulations (VLES) based on the lattice Boltzmann method (LBM) were conducted to resolve unsteady flow structures. In the B9 case, the reduced baffle density allowed for continuous flow development with minimal resistance, resulting in enhanced vertical momentum and strong upward propagation at the outlet. In contrast, the B17 configuration exhibited significant flow deceleration, restricted flow channels, and prominent recirculation zones between adjacent baffles. As a result, exhaust jet flow beyond 7 meters from the outlet was only observed in the B9 configuration. These findings demonstrate that the number of internal baffles critically influences the momentum transfer and far-field dispersion characteristics of exhaust stack flows, offering valuable insights for the aerodynamic optimization of noise control devices. - COLLAPSE
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HIGH-FIDELITY LBM ANALYSIS OF INTERNAL FLOW STRUCTURES IN AN EXHAUST STACK SYSTEM WITH VARYING NUMBERS OF ACOUSTIC BAFFLES
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Original Article
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COMPUTATIONAL PREDICTION OF TRANSONIC SHOCK AND HIGH SPEED IMPULSIVE NOISE USING LBM SIMULATION
LBM 해석을 이용한 천음속 충격파 및 고속 충격 소음 예측 연구
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K. T. Park, D. Jeong, D. B. Jung, R. S. Myong, H. Lee
박규태, 정도윤, 정다빈, 명노신, 이학진
- With the increasing demand for high-speed operation of next-generation rotorcraft, transonic flow phenomena and the associated high-speed impulsive (HSI) noise generated by …
- With the increasing demand for high-speed operation of next-generation rotorcraft, transonic flow phenomena and the associated high-speed impulsive (HSI) noise generated by rotor blades have attracted attention. Under high-speed operating conditions, locally transonic flow develops on the advancing side of the rotor blade, leading to the formation of strong shock waves on the blade surface. These shock waves degrade aerodynamic performance and act as the dominant source of HSI noise affecting the far-field acoustic environment. Although the importance of transonic shock-induced noise has been widely recognized, reliable verification of high-fidelity numerical approaches remains essential. In this study, Lattice Boltzmann Method (LBM) coupled with a Ffowcs Williams–Hawkings (FW-H) acoustic formulation based on permeable surface is applied to analyze transonic shock structures and HSI noise characteristics of rotor systems. To assess the capability of the numerical framework, transonic flow simulations are first conducted for the two-dimensional RAE 2822 airfoil and the three-dimensional ONERA M6 wing. The results show that the LBM simulations accurately predict shock locations and pressure recovery characteristics, exhibiting good agreement with experimental pressure coefficient distributions in both two- and three-dimensional transonic benchmark cases. The validated approach is extended to a 1/7-scale UH-1H helicopter rotor under hovering conditions to investigate the effects of tip Mach number on shock formation and HSI noise generation. The simulations capture the development of spiral shock structures on the rotor disk, which become more pronounced as the tip Mach number increases. Far-field acoustic predictions obtained using the permeable FW-H formulation successfully predict the variation of HSI noise with tip Mach number and show a good agreement with experimental measurements. Overall, the present study confirms that the LBM combined with permeable FW-H approach is a physically reliable framework for predicting transonic shock structures and HSI noise of rotorcraft. - COLLAPSE
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COMPUTATIONAL PREDICTION OF TRANSONIC SHOCK AND HIGH SPEED IMPULSIVE NOISE USING LBM SIMULATION
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Original Article
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MID-FIDELITY AEROACOUSTIC ANALYSIS OF A LIFT-OFFSET COAXIAL ROTOR IN FORWARD FLIGHT
중 충실도 기반의 Lift-Offset 동축반전 로터의 전진 비행 공력 소음 해석
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S. C. Lee, Y. S. Lim, Y. S. Jung
이시찬, 임유상, 정용수
- This study established a mid-fidelity analysis framework by coupling a vortex particle method (VPM)-based aerodynamic solver with a comprehensive rotorcraft analysis code …
- This study established a mid-fidelity analysis framework by coupling a vortex particle method (VPM)-based aerodynamic solver with a comprehensive rotorcraft analysis code to investigate the aerodynamic and aeroacoustic characteristics of a coaxial lift-offset rotor system. Using the developed framework, the effects of rotor shaft tilt, lift offset, and flight speed on aerodynamic interactions and noise characteristics were analyzed. The results showed that variations in shaft tilt altered the aerodynamic load distribution and noise directivity, with aeroacoustic noise induced by inter-rotor interactions being particularly dominant. As the lift offset increased, the aerodynamic loading increased on the advancing side but decreased on the retreating side. Overall, higher lift-offset conditions reduced aeroacoustic noise in the forward region of the rotor disk and on the retreating side. As flight speed increased, the blade–vortex interaction (BVI) region shifted aft, and the intensity of aerodynamic load fluctuations increased. In particular, under the 200-knot condition, abrupt load fluctuations caused by BVI were identified as a primary contributor to high-frequency aeroacoustic noise. The developed framework demonstrated its ability to capture the complex aerodynamic interactions and aeroacoustic characteristics of coaxial rotor systems and is expected to serve as an efficient tool for evaluating rotor performance and noise during the preliminary design stage. - COLLAPSE
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MID-FIDELITY AEROACOUSTIC ANALYSIS OF A LIFT-OFFSET COAXIAL ROTOR IN FORWARD FLIGHT
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Original Article
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DESIGN OPTIMIZATION OF INBOARD AIRFOIL FOR A COAXIAL ROTOR USING AN ANN PREDICTION MODEL
인공신경망 예측 모델 기반 동축 반전 로터의 안쪽 익형 최적 설계
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M.S. Kim, S.C. Lee, Y.S. Lim, Y.S. Jung
김무성, 이시찬, 임유상, 정용수
- An artificial neural network(ANN)-based surrogate optimization framework was developed to enhance the aerodynamic performance of a lift-offset coaxial rotor’s inner airfoil under …
- An artificial neural network(ANN)-based surrogate optimization framework was developed to enhance the aerodynamic performance of a lift-offset coaxial rotor’s inner airfoil under reverse flow. At high advance ratios, reverse flow over the inboard retreating blade causes the geometric trailing edge to act as a leading edge, inducing early separation, negative lift, and high profile drag. Although double-ended airfoils mitigate these penalties, the link between sectional improvements and integrated rotor performance remains unclear. Using the Sikorsky DBLN-526 as a baseline, the airfoil geometry was parameterized via the class-shape transformation(CST) method. An ANN model, trained on a 2D RANS CFD database, predicted aerodynamic coefficients, and was coupled with a genetic algorithm for multi-objective optimization. The optimized airfoils were evaluated through XH-59A coaxial rotor performance analysis. Results show that drag reduction at negative deep stall angle of attack provides limited rotor-level benefits. Conversely, drag reduction and lift enhancement at low angles of attack reduce the required pitch and effective angle of attack over the rotor disk, lowering profile drag and torque. The lift-enhancement optimized airfoil improved the rotor lift-to-drag ratio by 4.1% over the baseline. High-speed coaxial rotor inner airfoil design thus requires coupled consideration of sectional characteristics, rotor trim, and effective angle of attack distribution. - COLLAPSE
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DESIGN OPTIMIZATION OF INBOARD AIRFOIL FOR A COAXIAL ROTOR USING AN ANN PREDICTION MODEL
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Original Article
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COMPUTATIONAL ANALYSIS OF LEAKAGE OF LIQUEFIED AMMONIA IN SHALLOW WATER
암모니아의 천수 수중 누출 전산 해석 연구
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S. Lee, W.J. Lee, S. Lee
이슬기, 이원주, 이승수
- This study presents a computational fluid dynamics (CFD) analysis of liquefied ammonia leakage from a pressurized storage tank in shallow-water environments. As …
- This study presents a computational fluid dynamics (CFD) analysis of liquefied ammonia leakage from a pressurized storage tank in shallow-water environments. As ammonia is increasingly considered a carbon-free marine fuel, understanding its leakage behavior and phase change characteristics is essential for safety assessment. Transient simulations were performed using ANSYS Fluent. The Eulerian multiphase model was applied to represent the interaction between seawater, air, liquid ammonia, and ammonia vapor, and the Lee Model was used to simulate the evaporation process. To investigate the influence of tank size on leakage behavior, three tank volumes (4, 8, and 16 m3) were analyzed under identical leakage conditions. A three-dimensional simulation for the 8 m3 case was first conducted and compared with a two-dimensional analysis, confirming that the 2D model can reasonably reproduce the early-stage leakage behavior. The results show that the tank pressure rapidly decreases after leakage and gradually approaches the surrounding hydrostatic pressure. Liquid ammonia mass decreases due to leakage and evaporation, while ammonia vapor increases and rises due to buoyancy. Larger tank volumes tend to exhibit relatively lower evaporation ratios under identical leakage conditions. These results provide fundamental data for evaluating ammonia leakage scenarios and safety assessments in marine environments. - COLLAPSE
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COMPUTATIONAL ANALYSIS OF LEAKAGE OF LIQUEFIED AMMONIA IN SHALLOW WATER
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Original Article
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PREDICTION OF DISCHARGE CAPACITY ACCORDING TO EOS MODELS FOR POSRV IN HYDROGEN REFUELING STATIONS
수소충전소용 파일럿형 안전릴리프 밸브의 상태방정식 모델에 따른 분출용량 추정 관련 연구
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E.J. Jo, S.H. Han, G.B. Min
조은진, 한승호, 민경범
- In high-pressure gaseous hydrogen refueling stations, the discharge capacity of a pilot- operated safety relief valve(POSRV) is a key design parameter for …
- In high-pressure gaseous hydrogen refueling stations, the discharge capacity of a pilot- operated safety relief valve(POSRV) is a key design parameter for overpressure protection. At an inlet pressure of 87.5 MPa, however, hydrogen exhibits pronounced real gas behavior, and the API 520 methodology, which assumes ideal gas isentropic nozzle flow, may not accurately predict the discharge capacity. As no domestic facility is available for certified discharge capacity testing, a model-based approach is required. In this study, the POSRV discharge capacity was evaluated using six approaches: the API 520 analytical equation, a modified API formulation incorporating the real gas compressibility factor and isentropic exponent, and CFD simulations employing the ideal gas, NIST REFPROP, Peng-Robinson(PR), and Aungier-Redlich-Kwong(Aungier-RK) equations of state. Analyses were performed at -40°C, 20°C, and 170°C under 87.5 MPa, with the REFPROP result used as the reference. All approximate methods overpredicted the discharge capacity, with the largest deviations for the API 520 and ideal gas models; the discrepancies decreased with increasing temperature, while the Aungier-RK model showed the closest agreement with the reference. These findings demonstrate that the ideal-gas assumption and simplified API formulations can significantly overestimate discharge capacity at lower temperatures, and that accurate prediction requires rigorous representation of real gas properties, particularly density and speed of sound. - COLLAPSE
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PREDICTION OF DISCHARGE CAPACITY ACCORDING TO EOS MODELS FOR POSRV IN HYDROGEN REFUELING STATIONS
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Original Article
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ANALYSIS OF THE PROPULSION EFFICIENCY OF SWIMMING FLIPPERS USING AN OVERSET MESH METHOD AND A TWO-WAY FLUID-STRUCTURE INTERACTION TECHNIQUE
중첩격자기법과 양방향 유체-구조 상호작용 기법을 이용한 수영용 오리발의 추진효율 해석
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C. An, N. Hur
안찬영, 허남건
- Swimming flippers with flexible structures have long been employed as effective underwater propulsion devices. In this study, numerical simulations were performed to …
- Swimming flippers with flexible structures have long been employed as effective underwater propulsion devices. In this study, numerical simulations were performed to analyze the propulsion efficiency of swimming flippers by considering various structural and kinematic parameters. An overset mesh method combined with a two-way fluid- structure interaction (FSI) technique was adopted to capture the deformation of the flipper and the resulting flow field interactions. The results revealed that the proposed quasi-steady propulsion efficiency increased as stiffness decreased in the range of stiffness considered in the present study. The efficiency showed a peak value at a certain amplitude, while it continuously increased with increasing frequency and flipper length within the range considered in the present study. These findings can provide design guidelines for optimizing swimming flippers and related underwater propulsion systems. - COLLAPSE
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ANALYSIS OF THE PROPULSION EFFICIENCY OF SWIMMING FLIPPERS USING AN OVERSET MESH METHOD AND A TWO-WAY FLUID-STRUCTURE INTERACTION TECHNIQUE
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Original Article
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NUMERICAL INVESTIGATION OF THE PERFORMANCE VARIATION OF A FAN-HEAT EXCHANGER SYSTEM FOR POWER TRANSFORMERS UNDER EXTERNAL WIND CONDITIONS
외부 풍속 조건에 따른 발전소용 주변압기 팬-열교환기 시스템의 성능변화에 관한 수치적 연구
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B.G. Cha, S. Park, K. Park, J.K. Min
차백곤, 박성호, 박경욱, 민준기
- This study applied a simplified system-level CFD model to evaluate the cooling performance of an outdoor air-cooled fan–heat exchanger system for a …
- This study applied a simplified system-level CFD model to evaluate the cooling performance of an outdoor air-cooled fan–heat exchanger system for a power-plant transformer under various external wind conditions. The fan was modeled using the pressure-jump method, while the heat exchanger core was simplified using an air/oil-coupled dual-cell porous media model combined with an ε-NTU heat transfer model. This approach enables the flow rate and heat transfer performance of the system to be evaluated under various external wind conditions without directly resolving the detailed fin-tube geometry or fan blades. The external wind conditions were determined based on meteorological data from the power-plant installation region, with wind speeds ranging from 0 to 20 m/s and wind directions of γ = 0°, 45°, and 90°. The results showed that the frontal wind condition, γ = 0°, caused the most significant performance degradation, with the heat transfer rate and fan flow rate decreasing by up to approximately 52% and 50%, respectively, compared with the calm (no wind) condition. Meanwhile, under the crosswind condition of γ = 90°, the heat transfer performance decreased even though the fan flow rate increased. This indicates that wind-induced distortion of the fan outlet flow can reduce the effective cooling performance of the system. Therefore, the proposed simplified CFD can be applied to evaluating system-level cooling performance variations caused by fan operating-point shifts and fan outlet flow distortion under external wind conditions. - COLLAPSE
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NUMERICAL INVESTIGATION OF THE PERFORMANCE VARIATION OF A FAN-HEAT EXCHANGER SYSTEM FOR POWER TRANSFORMERS UNDER EXTERNAL WIND CONDITIONS
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Original Article
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ANALYSIS OF NPSHR CHARACTERISTICS ACCORDING TO VARIATIONS IN INDUCER PARAMETERS OF A DEEPWELL PUMP
Deepwell Pump의 Inducer 형상 파라미터 변화에 따른 NPSHr 특성 분석
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M. Choi, S. Park, D. Kim, J. Jeon, K. Chang
최민준, 박상환, 김동, 전종현, 장경식
- This study numerically investigates the effects of inducer geometry parameters on the required net positive suction head (NPSHr) of a deepwell pump. …
- This study numerically investigates the effects of inducer geometry parameters on the required net positive suction head (NPSHr) of a deepwell pump. The design variables considered in this study were the number of inducer blades, blade thickness, and leading-edge angle. A total of 45 cases were analyzed by varying the number of blades from two to four, the blade thickness from 2.0 to 4.5 mm, and the leading-edge angle from −10° to +10°. The NPSHr was determined as the net positive suction head available (NPSHa), which indicates the available suction head above the vapor pressure, at which the total head decreased by 3% from the non-cavitating reference head for each geometry condition. The results showed that the number of blades had the most significant influence on NPSHr. The two-blade inducer showed the lowest NPSHr over the entire range of leading-edge angles due to its wider flow passage and lower solidity, resulting in improved suction performance. In contrast, the four-blade inducer showed the highest NPSHr and the greatest sensitivity to leading-edge angle variation because of increased blockage and local pressure reduction. The blade thickness also affected NPSHr, with thicker blades generally increasing NPSHr due to reduced flow passage area. These results indicate that reducing the blade number and avoiding excessive positive leading-edge angles are effective design strategies for improving the suction performance of a deepwell pump inducer. - COLLAPSE
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ANALYSIS OF NPSHR CHARACTERISTICS ACCORDING TO VARIATIONS IN INDUCER PARAMETERS OF A DEEPWELL PUMP
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Original Article
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NUMERICAL INVESTIGATION OF THE IMPACT DYNAMICS OF A VISCOELASTIC DROPLET ON A SOLID SURFACE
고체 표면에 충돌하는 점탄성 액적의 동역학적 거동에 대한 수치해석 연구
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H. Kwon, T. Ha, S. Shin
권희원, 하태진, 신승원
- Droplet impact on solid surfaces plays an important role in inkjet printing, spray coating, food processing, and biomedical applications. Although many studies …
- Droplet impact on solid surfaces plays an important role in inkjet printing, spray coating, food processing, and biomedical applications. Although many studies have investigated Newtonian droplets, practical fluids often exhibit viscoelastic behavior, which makes the spreading dynamics more complex due to the generation and relaxation of elastic stress. In particular, the maximum spreading diameter of a viscoelastic droplet cannot be fully explained by conventional Newtonian-based models. In this study, the impact dynamics of a viscoelastic droplet on a solid surface are investigated using the Level Contour Reconstruction Method combined with the Oldroyd-B constitutive model. The effects of Reynolds number, solvent viscosity ratio, and Weissenberg number on the maximum spreading diameter are examined and compared with Newtonian fluid cases. The results show that the maximum spreading behavior of viscoelastic droplets is not governed solely by Reynolds number or total viscosity, but is also affected by the relative contribution and relaxation behavior of viscoelastic stress. - COLLAPSE
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NUMERICAL INVESTIGATION OF THE IMPACT DYNAMICS OF A VISCOELASTIC DROPLET ON A SOLID SURFACE
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Original Article
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NUMERICAL ANALYSIS FOR A SELF-PRESSURIZED LIQUEFIED HYDROGEN STORAGE TANK USING OPENFOAM
OpenFOAM을 활용한 액화수소 저장탱크 자가가압 수치해석
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S. Ahn, S. Park
안서연, 박선호
- As liquefied hydrogen (LH2) emerges as a key future energy carrier, reliable prediction of its phase-change behavior during self-pressurization is …
- As liquefied hydrogen (LH2) emerges as a key future energy carrier, reliable prediction of its phase-change behavior during self-pressurization is essential for the design and operation of LH2 storage and receiving terminals. In this study, the phase change within a self-pressurized LH2 tank was numerically investigated using OpenFOAM. The simulation modeled the self-pressurizing tank tested at the NASA Multipurpose Hydrogen Test Bed (MHTB). Two solvers were compared: an Euler-Euler two-fluid solver, which solves governing equations for each phase separately, and a Volume of Fluid (VOF) solver, which treats both phases with a single set of equations while capturing the interface. To examine turbulence effects, results from the k-ω SST, buoyant k-ε, and LES-WALE models were evaluated against those of laminar flow. For phase change, the Lee and Schrage models were assessed. The Euler-Euler solver slightly overpredicted the tank pressure, whereas the VOF solver demonstrated closer agreement with the experimental data. Among the turbulence treatments, both the laminar assumption and LES captured the experimental trends well, while the Schrage model exhibited superior performance among the phase- change models. Overall, the internal pressure of the MHTB was predicted with a mean absolute error of approximately 1.8 kPa, and key phenomena, including boil-off gas (BOG), boil-off rate (BOR), thermal stratification, and internal flow fields, were accurately reproduced. - COLLAPSE
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NUMERICAL ANALYSIS FOR A SELF-PRESSURIZED LIQUEFIED HYDROGEN STORAGE TANK USING OPENFOAM
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Original Article
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BUBBLE ENTRAPMENT DURING DROPLET IMPACT IN THE LOW-WEBER-NUMBER REGIME: EFFECT OF HYDROPHOBICITY AND IMPLICATIONS FOR WEAPON ENGINEERING
낮은 웨버 수에서의 액적 충돌로 인한 기포의 포집특성: 소수성의 영향과 무기공학적 고찰
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H. Cho, J. Song, J. Kwon, I. Yoon
조현재, 송주한, 권재현, 윤익로
- This study numerically investigates bubble entrapment and impact-force dynamics during low-Weber-number droplet impact on hydrophobic and superhydrophobic surfaces. Surface wettability significantly affected …
- This study numerically investigates bubble entrapment and impact-force dynamics during low-Weber-number droplet impact on hydrophobic and superhydrophobic surfaces. Surface wettability significantly affected bubble entrapment: a small bubble remained attached to the hydrophobic surface, whereas a larger bubble was entrapped inside the droplet on the superhydrophobic surface. Both cases showed force fluctuations and a singular peak, while pronounced residual oscillations appeared only on the superhydrophobic surface due to bubble oscillation. These results highlight the importance of dynamic droplet-impact loads in compact engineering and defense systems. - COLLAPSE
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BUBBLE ENTRAPMENT DURING DROPLET IMPACT IN THE LOW-WEBER-NUMBER REGIME: EFFECT OF HYDROPHOBICITY AND IMPLICATIONS FOR WEAPON ENGINEERING
Journal Informaiton
Journal of Computational Fluids Engineering
Journal of Computational Fluids Engineering
Korean Society for Computational Fluids Engineering
한국전산유체공학회
#1002, 20, Teheran-ro 25-gil, Gangnam-gu, Seoul 06132, Korea
Tel: 82-2-701-8992 / E-mail: kscfe@kscfe.or.kr Copyright© Korean Society for Computational Fluids Engineering. Powered by APUB
Tel: 82-2-701-8992 / E-mail: kscfe@kscfe.or.kr Copyright© Korean Society for Computational Fluids Engineering. Powered by APUB