Journal of the Korean Society for Precision Engineering

Aerodynamic Flow Characteristics Inducing Centrifugal Compressor Noise Generation in High-speed Turbomachinery: Jihun Song, Chang Ho Son, Dong-Ryul Lee; J. Korean Soc. Precis. Eng. 2025;42(9):763-770.
Published online September 1, 2025; DOI: https://doi.org/10.7736/JKSPE.025.088

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Centrifugal compressor is a device that converts kinetic energy to increase the air pressure. It rotates at a high speed of up to 200,000 RPM and directly affects aerodynamic noise. Various studies have already been conducted, but the direct calculation method of acoustics based on the unsteady solution is inefficient because it requires a lot of resources and time. Therefore, flow characteristics and numerical comparison according to various aerodynamic factors predicted as a cause of noise generation were analyzed in this study based on the steady solution. High-frequency noise was calculated locally near the asymmetric flow properties. Vortex and turbulent kinetic energy were generated at similar locations. Among static components, a large-sized vortex of 3.48×10⁷ s^-1 was distributed at the location where the rotational flow around the compressor wheel combined with the inlet suction flow. In addition, a locally high vortex of 8.16×10⁵ s^-1 was distributed around the balancing cutting configurations that cause asymmetric flow characteristics. Analysis of these factors and causes that directly affect noise can be efficiently improved in the pre-design stage. Therefore, the efficient design methodology for centrifugal compressors that considers both performance and noise is expected based on the results of this study.

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An Aeroacoustics Study on AAM Blade in Duct with Different Strut Shapes: Sang Hyun Kim, Jihun Song, Dong-Ryul Lee; J. Korean Soc. Precis. Eng. 2023;40(9):751-758.
Published online September 1, 2023; DOI: https://doi.org/10.7736/JKSPE.023.060

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Lately, due to the concentration of population in metropolitan areas, traffic congestion in the hub city has occurred, and future mobility AAM development is undergoing active progress to solve this situation. Accordingly, reducing noise pollution, which is pointed out as one of the problems of AAM, is an essential technical issue for urban operation. In this study, a duct, which is a representative aerodynamic noise reduction method, was used, and numerical analysis was performed using ANSYS FLUENT, a CFD software, according to the shape of struts in the duct. The FW-H of the transient-state LES model was used, and the steady-state analysis value was used as the initial value to save analysis time. Case 1 without strut, Case 2 with strut of an airfoil section, and Case 3 with strut of a rectangle section were designed and compared at a rotational speed of 6,000 RPM. Compared to Case 1, Case 2 and Case 3 showed improved thrust by about 7% and 2%, respectively. Compared to Case 2, Case 3 showed reduced OASPL from a minimum of 0.0793 dB to a maximum of 1.0072 dB. It was found that shapes of strut in the duct significantly affect thrust and aerodynamic noise.

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A Study on Aerodynamic Noise Reduction Depending on UAM Main Propeller Lay-out: Chang Ho Son, Jihun Song, Dong-Ryul Lee; J. Korean Soc. Precis. Eng. 2023;40(9):741-750.
Published online September 1, 2023; DOI: https://doi.org/10.7736/JKSPE.023.059

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Recently, as UAM has been in the spotlight worldwide, the issue of aerodynamic noise generated from propellers has emerged. Therefore, changes in thrust and aerodynamic noise were compared while changing the propeller lay-out distance. The designed propeller model was analyzed using ANSYS Fluent, a CFD software. Based on steady-state analysis, transient analysis was performed, and SPL was calculated using the FW-H noise model. Based on the standard propeller lay-out distance of 0.1 R (0.12 mm), 5 cases from 0.2 R to 0.6 R were compared with the reference model at equal intervals of 0.1 R. The thrust increased by up to 3.5% as the propeller distance increased. In most listeners positioned to measure SPL, noise was reduced by 0.07-0.7% in the improved model compared to the reference model due to reduction in local vorticity. However, because pressure fluctuation due to the increase in thrust and high SPL in the low-frequency region were measured, noise increased by 0.6% to 3.5% in some listeners. Increasing the propeller distance enhances thrust performance, but inevitably increases noise due to pressure fluctuations and SPL in the low-frequency region. Therefore, strict analysis of noise prediction according to a specific frequency and various design shapes are needed.

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A Study on Aerodynamic and Acoustic Characteristics of Blades by Biomimetic Design for UAM: Chang Ho Son, Sang Hyun Kim, Jihun Song, Dong-Ryul Lee; J. Korean Soc. Precis. Eng. 2023;40(7):571-580.
Published online July 1, 2023; DOI: https://doi.org/10.7736/JKSPE.023.018

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Urban air mobility (UAM) is rapidly growing as a new means of transportation. As a result, noise pollution is emerging as a new technical challenge. Therefore, the sawtooth-shaped biomimetic designs were incorporated on the trailing edge of the blade to reduce flow-induced noise. The biomimetic virtual design was analyzed using the CFD software, ANSYS FLUENT V20.2. Based on the steady-state RANS flow solution, the acoustic power was calculated using the broadband noise source model to evaluate acoustic radiation. Four different cases with cutting lengths of 3.1 mm, 3.7 mm, 4.3 mm, and 4.9 mm of blades were compared with the base model at the rotational blade speed of 6,000 RPM. The maximum acoustic power level of the biomimetic blades ranged from 37.24 dB to 39.88 dB, resulting in a 10% reduction compared to the original blade (42.02 dB). The novel design affected the blade area, which inevitably reduced the slight thrust performance. However, the thrust was reduced to approximately less than 5% compared with the base blade in case 1. The biomimetic blade reduced the thrust due to its aerodynamic characteristics. However, the design of a blade with an appropriate cutting length has a greater effect in reducing noise rather than thrust.

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Propeller Modification with Groove Structure on Thrust Performance
Duygu Özyurt, Hürrem Akbıyık
Celal Bayar Üniversitesi Fen Bilimleri Dergisi.2025; 21(1): 27. CrossRef

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Smart Design of Rotor and Permanent Magnet considering Torque and Torque Ripple of Interior Permanent Magnet Synchronous Motor of Electric Vehicle: Seong-Hwan Bang, Si-Mok Park, Min-Gi Chu, Ji-Hun Song, Dong-Ryul Lee; J. Korean Soc. Precis. Eng. 2021;38(8):605-612.
Published online August 1, 2021; DOI: https://doi.org/10.7736/JKSPE.021.043

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The aim of this research was to investigate the torque performance of the motor in an electric vehicle depending on the rotor shape and air gap. The research focused on numerical comparison of torque performance of new rotors based on the average torque and torque ripple rate, which appeared according to the number and placement of permanent magnets. This research was numerically analyzed by MAXWELL V21.1. Average torque values in cases 1, 2, and 3 were increased, but vibration and noise in cases 1 and 3 were increased as the torque ripple rate increased. Considering the average torque and torque ripple rate, the torque performance of case 2 was the most optimal. Compared with Model N, the average torque of case 2 was increased by 9.1% and the torque ripple rate was reduced by 1.5%. The torque performance according to the size of air gap was compared with the basic model of case 2, which showed the best performance. An air gap of 0.7 mm applied to Model N showed the best torque performance. An additional magnet on case 2 and air gap of 0.7 mm provided the best torque performance and improved the driving motor performance for motor durability.

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Vehicle-motion-based Front Wheel Steer Angle Estimation for Steer-by-Wire System Fault Tolerance
Seungyong Choi, Wanki Cho, Seung-Han You
Journal of the Korean Society for Precision Engineering.2024; 41(5): 347. CrossRef
Numerical Analysis of Outer-Rotor Synchronous Motors for In-Wheel E-Bikes: Impact of Number of Windings, Slot, and Permanent Magnet Shapes
Jaewoong Han, Chanyoung Jin, Insu Cho, Jinwook Lee
Applied Sciences.2024; 14(10): 4167. CrossRef

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A Study on the Smart Design and Cooling Performance of Electric Vehicle Motor Using Metal-Hybrid Materials: Sung-Hwan Bang, Dong-Ryul Lee; J. Korean Soc. Precis. Eng. 2021;38(8):595-603.
Published online August 1, 2021; DOI: https://doi.org/10.7736/JKSPE.021.039

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The aim of this study is to numerically investigate the cooling performance of the electric vehicle motor depending on the attachment of the heat sink and materials to the cooling channel. The research focused on the numerical comparison of forced convective heat transfer coefficients with case 1 (Heat Sink-None, Cooling Channel-Al), case 2 (Heat Sink-None, Cooling Channel-Metal Hybrid Material), case 3 (Heat Sink-4EA, Cooling Channel-Al), and case 4 (Heat Sink-6EA, Cooling Channel-Al). To compare the cooling performance for novel design of the smart cooling system, selected local positions for various temperature distributions were marked on the coil surface. Normalized local Nusselt number of the cooling area at the normalized width position indicated that cooling performance of case 1 was on an average 8.05, 0.57, and 5.85% lower than that of cases 2, 3, and 4, respectively.

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Vehicle-motion-based Front Wheel Steer Angle Estimation for Steer-by-Wire System Fault Tolerance
Seungyong Choi, Wanki Cho, Seung-Han You
Journal of the Korean Society for Precision Engineering.2024; 41(5): 347. CrossRef

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Novel Design of Cooling Channel Utilizing Pin-Fin Vortex Generators in Electric Vehicle Driving Motor: Min-Gi Chu, Dong-Ryul Lee; J. Korean Soc. Precis. Eng. 2021;38(7):491-500.
Published online July 1, 2021; DOI: https://doi.org/10.7736/JKSPE.021.023

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The objective of this study was to numerically accomplish the cooling performance of an electric vehicle driving motor depending on cooling channel design. Cooling performances of novel cooling channels were compared based on the temperature of coils and cooling channels as well as convection heat transfer coefficient in electric vehicle driving motors. Local axial positions of cooling channels at three different cases were marked for numerical comparison of heat transfer coefficients. Owing to forced convection by the boundary and flow conditions, the heat transfer coefficient of Case 3 at the location where pin-fins were attached in the cooling channel was improved 85.02 and 65.77% compared to Cases 1 and 2, respectively. In Case 3 with pin-fins having 50% of cooling channel length, the maximum temperature of the coil was 4.25% lower than that of Case 2 with pin-fins having 30% of the cooling channel length and 6.98% lower than that of Case 1 without pin-fins in the cooling channel. As a result, pin-fins finally diminished the maximum temperature of coils in Cases 2 and 3. Ultimately, Case 3 showed the best cooling performance for improving vehicle driving durability and developing next-generation electric vehicle cooling system technologies.

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Smart Cooling System Design for Augmentation of Cooling Performance of Electric Vehicle Driving Motor Utilizing Cooling Channel Fin: Si-Mok Park, Dong-Ryul Lee; J. Korean Soc. Precis. Eng. 2021;38(6):427-439.
Published online June 1, 2021; DOI: https://doi.org/10.7736/JKSPE.021.020

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This research is to investigate the cooling performance of the motor in the electric vehicle depending on the cooling channel fin. The research focused on numerical study of the temperature of coil and cooling channel and the heat transfer coefficients to find a optimum design shape with high cooling performance at three different cases. To compare the convective cooling performance of the three cooling channels, local position (R) are displayed on the surface of the coils with a large temperature deviation. This research was performed on forced convection and was numerically analyzed by FLUENT V20.2. Owing to forced convection by the same mass flow, the average cooling channel velocity in Case 3 was 17.4% faster than Case 1 and 8.6% faster than Case 2. Out of the three cases, the highest heat transfer coefficient was found in the cooling channel and coil of Case 3, which had two cooling fins. The coil maximum temperature of Case 3 with 2 cooling fins was 4.7% lower than Case 1 without cooling fins and 1.7% lower than Case 2 with 1 cooling fin. Ultimately, Case 3 with two cooling fins provided the best cooling performance and improved driving motor performance for motor durability.

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Thermal management strategies and power ratings of electric vehicle motors
Jaya Antony Perinba Selvin Raj, Lazarus Godson Asirvatham, Appadurai Anitha Angeline, Stephen Manova, Bairi Levi Rakshith, Jefferson Raja Bose, Omid Mahian, Somchai Wongwises
Renewable and Sustainable Energy Reviews.2024; 189: 113874. CrossRef

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A Study on Cooling Performance of Electric Vehicle Motor for Different Cooling Channel Shapes: Si-Mok Park, Seong-Hwan Bang, Min-Gi Chu, Ji-Hun Song, Dong-Ryul Lee; J. Korean Soc. Precis. Eng. 2021;38(6):417-425.
Published online June 1, 2021; DOI: https://doi.org/10.7736/JKSPE.021.019

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This research investigated the cooling performance of the motor in electric vehicle depending on the shape of the cooling channel. The research, conducted numerically by FLUENT V20.1, focused on the numerical study of heat transfer coefficients to find an optimum design shape with high cooling performance. To compare the cooling performance, the temperatures in the coil and cooling channel were analyzed. As a result of forced convection, the average cooling channel velocity of Case 2 was 38% faster than Model N and 34% faster than Case 1. The maximum temperature of the cooling channel of Case 2 was 8.7% lower than Model N and 5.6% lower than Case 1. The minimum temperature of the coil of Case 2 was 2.7% lower than Model N and 4.3% lower than Case 1. The maximum temperature of the coil of Case 2 was 4.6% lower than Model N and 2.9% lower than Case 1. Ultimately, cooling channel of Case 2 showed the best cooling performance and improved driving performance for motor durability.

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Development of a novel electro-mechanical brake motor thermal management system for nonuniform heating under extreme thermal conditions
Piljun Park, Hongseok Choi, Sangwook Lee, Sunoh Jeong, Hoseong Lee
Energy Conversion and Management.2025; 325: 119406. CrossRef

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A Study on Aero-Acoustics of High-Speed Turbomachinery for Different Rotational Speeds: Ji-Hun Song, Dong-Ryul Lee; J. Korean Soc. Precis. Eng. 2020;37(12):897-904.
Published online December 1, 2020; DOI: https://doi.org/10.7736/JKSPE.020.072

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This study is to numerically investigate the Aero-Acoustics of Turbocharger compressor. The turbocharger compressor is high-speed turbomachinery that rotates faster than 200,000 RPM. The Aero-Acoustics with five different rotational speeds (120,000, 150,000, 180,000, 200,000, and 220,000 RPM) is used herein. The fluid domain is designed by CATIA V5R21 and analyzed by ANSYS FLUENT V19.1 with compressible momentum equation. The Pressure-velocity coupling method of the solver is the coupled algorithm and calculated by a pressure-based method. Numerical analysis of the aero-acoustics by broadband noise sources model provides calculated sound-source and acoustic-level based on steady RANS. At the industrial site, it is important to quickly analyze the noise source. APL (Acoustic Power Level) with five different rotational speeds and sound characteristics based on flow factor at the compressor wheel was numerically calculated for the noise-based design. The maximum APL is located at blade tips in case of 120,000, 150,000 and 180,000 RPM. In the case of 200,000 RPM, the maximum APL is located at splitter tips. At more than 220,000 RPM, the maximum APL is located at the balancing cutting section of the wheel. In order to optimally design the high-speed turbomachinery, cutting sections and side locations of the wheel are essential factors to reduce physical noise.

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A Review on Flow Regimes and Aeroacoustic Coupling in Subsonic Flow Around Flat Plates
Atef El Khatib, Ahmad Al Miaari, Hassan Assoum, Ahmad Salem, Ali Hammoud
Arabian Journal for Science and Engineering.2025; 50(12): 8753. CrossRef
Aerodynamic Flow Characteristics Inducing Centrifugal Compressor Noise Generation in High-speed Turbomachinery
Jihun Song, Chang Ho Son, Dong-Ryul Lee
Journal of the Korean Society for Precision Engineering.2025; 42(9): 763. CrossRef

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Erratum to: A Study on Flow Characteristics and Cooling Performance for Different Turbine Blade Shapes: Chan Woo Park, Dong-Ryul Lee; J. Korean Soc. Precis. Eng. 2020;37(11):861-861.
Published online November 1, 2020; DOI: https://doi.org/10.7736/JKSPE.019.072

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Optimization Design for Augmentation of Cooling Performance Utilizing Leading-Edge Materials in Electric Vehicle Battery Cells: Byeong Yeop Kim, Dong-Ryul Lee; J. Korean Soc. Precis. Eng. 2020;37(7):529-538.
Published online July 1, 2020; DOI: https://doi.org/10.7736/JKSPE.020.044

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This study is to investigate the cooling performance of the battery in the electric vehicle depending on the attachment of the cooling plates and materials to the battery cells. Research focused on the numerical comparison of forced convective heat transfer coefficients with case 1(cell-Al, cooling plate-None), case 2(cell-Al, cooling plate-Al), case 3(cell-Al, cooling plate-C), and case 4(cell-C, cooling plate-Al). Normalized local Nusselt number of the cooling area at the normalized width position indicated that the heat transfer coefficient of the case 1 was averaging at 7, 14.5, 11.9% lower than that of case 2, case 3, and case 4. Based on case 3, the cooling performance with six different types of mass flow rates (0.05, 0.075, 0.0875, 0.1, 0.125, 0.15 kg/s) were compared. Normalized local Nusselt number at the normalized width position indicated that the heat transfer coefficient of 0.0875 kg/s was averaging at 35.8, 11.9% higher than that of 0.05, 0.075 kg/s and 12.3, 36.4, 60% lower than that of 0.1, 0.125, 0.15 kg/s. Ultimately, the best optimization design for air-cooling performance was case 3 with mass flow rate of 0.125 kg/s.

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A Study on Cooling Performance Augmentation of Water-Cooling and Optimization Design Utilizing Carbon Material in Electric Vehicle Secondary Battery: Seung Bong Hyun, Dong-Ryul Lee; J. Korean Soc. Precis. Eng. 2020;37(7):519-528.
Published online July 1, 2020; DOI: https://doi.org/10.7736/JKSPE.020.043

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This research is to investigate the augmentation of cooling performance of water-cooling in the electric vehicle secondary battery. The research focused on the numerical study of heat transfer coefficients for cooling performance augmentation. To improve the water-cooling performance with three different inlet sections of water-cooling and five different mass flow rates, air-cooling, and water-cooling were compared. To compare the water-cooling performance, selected local positions for various temperature distributions were marked on the battery cell surface. The normalized local Nusselt number of the cooling area at the normalized height position indicated that the heat transfer coefficient of the combined section was averaging at 77.95 and 58.33% higher than that of the circle and square, respectively. The heat transfer coefficient with the normalized width by water-cooling at combined section was averaging at 5.15 times higher than that of the air-cooling. At the normalized height, the cooling performance at the water flow rates of 10 Lpm was averaging at 68-74% higher than that of 5 Lpm and 35-39% lower than that of 25 Lpm. Ultimately, the best cooling performance existed with the combined section, and the water flow rate of 10 Lpm was most appropriate, given the temperature difference and power consumption.

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Influence of heat-transfer surface morphology on boiling-heat-transfer performance
RenDa He, ZhiMing Wang, Fei Dong
Heat and Mass Transfer.2022; 58(8): 1303. CrossRef

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A Study on Heat Radiation Performance for Different Layout of Electric Vehicle Secondary Battery Cell: Seung Bong Hyun, Byeong Yeop Kim, Ji Hun Song, Dong-Ryul Lee; J. Korean Soc. Precis. Eng. 2020;37(4):271-282.
Published online April 1, 2020; DOI: https://doi.org/10.7736/JKSPE.020.007

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This study is to investigate the cooling performance of the secondary battery in electric vehicles according to three different gaps between battery cells. To accomplish the convective cooling performance of the battery surface with three different gaps, selected local positions (X, Y, Z) for various temperature distributions were marked on the gap surface contacting the cell surface. The cooling performance of the gap of 0.5 mm was compared with the gaps of 5 mm, and 1 mm. Normalized local Nusselt number of the cooling area at the normalized width position indicated that the gap of 0.5 mm was on average 26.99% lower than that of 5 mm and 0.49% lower than that of 1 mm. At the normalized height, the gap of 0.5 mm was on average 12.12% higher than that of 1 mm. Because of the vortex at the outlet area, cooling performance at the gap of 0.5 mm was on average 13.19% higher than that of 5 mm and 0.79% higher than that of 1 mm at normalized thickness. Ultimately, the best cooling performance existed at the gap of 5 mm, but the gap of 0.5 mm was best for improving space efficiency, energy storage capacity, and vehicle-driving durability.

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A Study on Cooling Performance Augmentation of Water-Cooling and Optimization Design Utilizing Carbon Material in Electric Vehicle Secondary Battery
Seung Bong Hyun, Dong-Ryul Lee
Journal of the Korean Society for Precision Engineering.2020; 37(7): 519. CrossRef
Optimization Design for Augmentation of Cooling Performance Utilizing Leading-Edge Materials in Electric Vehicle Battery Cells
Byeong Yeop Kim, Dong-Ryul Lee
Journal of the Korean Society for Precision Engineering.2020; 37(7): 529. CrossRef

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A Study on Flow Characteristics and Cooling Performance for Different Turbine Blade Shapes: Chan Woo Park, Dong-Ryul Lee; J. Korean Soc. Precis. Eng. 2019;36(11):1043-1049.
Published online November 1, 2019; DOI: https://doi.org/10.7736/KSPE.2019.36.11.1043

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The purpose of this study was to investigate the flow characteristics and cooling performance for the heavy turbine blade with different shapes. Research was focused on the numerical study on forced convective heat transfer coefficients for three different blades with base, tip, and hole. Thus, selected local locations for various temperature distributions were shown in the flow domain. Final temperature on the local surface of blades was compared with three different blades. According to the results of velocity and temperature distributions in the fluid domain, the blade with holes had the best convective cooling performance with higher 13-16% average heat transfer coefficient than the other two blades. Apparent vortex at the tip of tip and hole blade caused the stable temperature drop. According to the calculations of local convective heat transfer coefficient between blade surface and atmosphere in the blade, approximately 18% of heat transfer coefficient at hole was higher than the base blade and 7% at hole blade was higher than the base blade. Lowest cooling performance existed at the center position of all three blades.