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.

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.

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.