Prapamonthon, Prasert

Preferred name

Alternative Name

PRAPAMONTHON, Prasert

Prapamonthon, P.

Main Affiliation

International Academy of Aviation Industry

prasert.pr@kmitl.ac.th

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Analysis of aerodynamic noise characteristics of high-speed train pantograph with different installation bases
(2019-06-01)
Yao, Yongfang
;
Sun, Zhenxu
;
Yang, Guowei
;
Liu, Wen
;
Prapamonthon, Prasert
The high-speed-train pantograph is a complex structure that consists of different rod-shaped and rectangular surfaces. Flow phenomena around the pantograph are complicated and can cause a large proportion of aerodynamic noise, which is one of the main aerodynamic noise sources of a high-speed train. Therefore, better understanding of aerodynamic noise characteristics is needed. In this study, the large eddy simulation (LES) coupled with the acoustic finite element method (FEM) is applied to analyze aerodynamic noise characteristics of a high-speed train with a pantograph installed on different configurations of the roof base, i.e. flush and sunken surfaces. Numerical results are presented in terms of acoustic pressure spectra and distributions of aerodynamic noise in near-field and far-field regions under up- and down-pantograph as well as flushed and sunken pantograph base conditions. The results show that the pantograph with the sunken base configuration provides better aerodynamic noise performances when compared to that with the flush base configuration. The noise induced by the down-pantograph is higher than that by the up-pantograph under the same condition under the pantograph shape and opening direction selected in this paper. The results also indicate that, in general, the directivity of the noise induced by the down-pantograph with sunken base configuration is slighter than that with the flush configuration. However, for the up-pantograph, the directivity is close to each other in Y-Z or X-Z plane whether it is under flush or sunken roof base condition. However, the sunken installation is still conducive to the noise environment on both sides of the track.
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Nucleate boiling enhancement on a pillar structure surface with selected surface vibration modes
(2024-08-01)
Ke, Zhaoqing
;
Mo, Zhenguo
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Zhang, Chaohua
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Prapamonthon, Prasert
;
Zhang, Ying
Pillar structure surfaces and surface vibrations are considered to be two individual techniques to enhance nucleate boiling. In this work, a volume of fluid (VOF) based numerical model is developed to study bubble growth promotion during nucleate pool boiling on a pillar structure surface under the aid of surface vibration. Three vibration modes of the pillar structure, including the horizontal vibration mode (HVM), vertical vibration mode (VVM) and angular vibration mode (AVM), are considered, and their effects on the bubble dynamics and heat transfer are discussed with various vibration amplitudes and frequencies. It is found that the pillar structure surface is favorable for bubble detachment as it constrains the bubble base radius and forces the bubble to grow more vertically compared to the plain surface. Although the HVM and AVM exert no or less vertical force component on the bubble for its detachment than the VVM does, but their horizontal force component significantly alters the bubble shape profile, breaks the force balance, and greatly increases the bubble departure frequency and heat transfer. The largest increment of liquid-vapor phase change rate is found to be 30.9% for the HVM. The bubble departure frequency and the vapor volume flux quantity increase with the pillar vibration amplitude and frequency. This work will deepen our understanding of fundamental bubble growth mechanisms as altered by vibration on the pillar structure surface for better heat transfer applications.
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Numerical investigation of the impact of wall boundaries on aerodynamic noise in high-speed trains
(2026-01-01)
Ma, Zhi Yuan
;
Feng, Qing Song
;
Prapamonthon, Prasert
;
Cheng, Gong
;
Sun, Zhen Xu
As the operating speed of high-speed trains continues to rise, aerodynamic noise has become a critical factor influencing train performance and passenger comfort, especially in confined environments like tunnels. In this study, a comprehensive simulation of the aerodynamic noise generated during the entire ‘open air-tunnel-open air’ transition at 450 km/h was performed using the improved delayed detached eddy simulation (IDDES) turbulence model and overset grid method, with results validated against field measurements. The findings reveal that, compared to open-air conditions, the tunnel environment induces higher-flow velocities around the train, stronger pressure fluctuations on the train surface, and more pronounced vortex shedding in the wake. Sound pressure levels (SPLs) at surface measurement points are typically about 10 dB(A) higher in the tunnel, with the primary differences observed in the 100–300 Hz frequency range, while both scenarios exhibit spectral peaks near 530 Hz. In the bogie region, tunnel noise is dominated by pressure-wave coupling and wall reflections, which amplify low- and mid-frequency components, whereas under open-air conditions, local vortex shedding and wake instabilities prevail, resulting in more high-frequency noise. The web structure contributes to the reduction of aerodynamic noise from the bogie area, with a particularly significant decrease observed in tunnel conditions. Along the tunnel wall, the SPL initially increases and then decreases, reaching a peak of 125.7 dB(A). After exiting the tunnel, the measurement points at Section L in the open air show a reduction of approximately 10 dB(A) compared to the corresponding tunnel-wall points. This study highlights the substantial amplification of low-frequency noise caused by wall confinement and demonstrates the noise-reduction potential of the web structure. The results provide valuable theoretical insights and numerical evidence for aerodynamic noise control in higher-speed train tunnels, offering significant engineering implications.
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Adsorption kinetic, equilibrium and thermodynamic study for the removal of Congo Red from aqueous solution
(2017-12-01)
Khan, Muhammad Imran
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Zafar, Shagufta
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Khan, Muhammad Ali
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Buzdar, Abdul Rehman
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Prapamonthon, Prasert
In this study, the adsorption of Congo red (CR) dye from aqueous solution onto cationic polymeric film (BIII) was investigated at ambient temperature. The effect of operational parameters such as contact time, membrane dosage, initial dye concentration and temperature on the adsorption of CR from aqueous solution was studied. Adsorption kinetics has been studied by employing several kinetic models and attained results showed that the adsorption data fitted-well to the pseudo-second-order kinetic model. Nonlinear forms of two parameters and three parameters isotherms were applied on experimental data and the results indicated that the adsorption data fitted well to the various two and three parameters isotherms. Thermodynamic study showed that the adsorption of CR onto cationic polymeric film (BIII) was an exothermic process.
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Aerodynamic optimization using passive control devices near the bogie cabin of high-speed trains
(2022-09-01)
Yao, Yongfang
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Sun, Zhenxu
;
Li, Guibo
;
Yang, Guowei
;
Prapamonthon, Prasert
Bogies are responsible for a significant amount of aerodynamic resistance and noise, both of which negatively affect high-speed train performance and passenger comfort. In the present study, the passive control method is applied in designing the bogie cabins of a high-speed train to improve its aerodynamic characteristics. Two passive control measures are introduced, namely, adding a spoiler and creating diversion grooves near the bogie cabins. Furthermore, the aerodynamic and aeroacoustic characteristics of a high-speed train operating at 350 km/h under different control strategies are numerically investigated using the improved-delayed-detached-eddy simulation (IDDES) and the acoustic finite element method (FEM). The impacts of passive control devices on drag reduction, slipstream, and aerodynamic noise are presented and discussed. Numerical results reveal that the passive control devices have a major effect on the slipstream around the train. The amplitude of the fluctuating pressure is higher in the first half of the train than in the second half. The first bogie has the maximum amplitude of the acoustic pressure for both the train with and without passive devices. In the far field, the spoiler installation and placement of the diversion grooves in the front of the bogie cabin can significantly reduce aerodynamic drag and noise. Hence, as shown in this study, using passive control methods to improve the aerodynamic and aeroacoustic properties of high-speed trains can be a viable option. [Figure not available: see fulltext.].
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Development and surface modification of anion exchange membrane for enhancement of antifouling potential in electrodialys process
(2018-01-01)
Khan, Muhammad Imran
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Zafar, Shagufta
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Khraisheh, Majeda
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Khan, Muhammad Ali
;
Buzdar, Abdul Rehman
The membrane fouling in the course of electrodialysis (ED) is a serious problem during water treatment which results to its shorter lifetime and higher energy consumption. Here, the antifouling property of previously reported BPPO-based anion exchange membranes (AEM) has been improved by surface coating with polydopamine (PDA). The modified and unmodified membranes were characterized in term of Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) water contact angle and water uptake. The antifouling potential was investigated in term of transition time, i.e. the time elapsed before the fouling took place.
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Hydrodynamic performance of a penguin wing: Effect of feathering and flapping
(2023-06-01)
Hao, Zhanzhou
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Yin, Bo
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Prapamonthon, Prasert
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Yang, Guowei
The penguin is the fastest underwater swimmer among the wing-propelled diving birds. To figure out the mechanism for its excellent swimming, the hydrodynamic performance of a penguin wing is numerically investigated using an immersed boundary method with the incompressible flow solver. This study examines the effects of feathering, flapping, and Strouhal number (St) under preset motion. Results indicate that feathering is the primary contributor to thrust generation. The change in angle of attack (AoA) can qualitatively reflect the change in lift but not thrust. Therefore, a new variable, angle of thrust (AoT, α<inf>T</inf>), is introduced to effectively reflect the change of thrust across different kinematic parameters. Optimal feathering amplitude balances the decrease in AoA and the increase in feathering angle to achieve the highest AoT and thrust. Excessive feathering amplitude degrades the leading-edge vortex to shear layers, transforms the pressure side to the suction side, and ultimately causes negative thrust (drag). Spatial analysis of the thrust shows that the outer three-fifths of the wing are the primary source of thrust, contributing 85.4% of thrust generation at optimal feathering amplitude. Flapping amplitude has little impact on the optimal feathering amplitude. The optimal feathering amplitude increases linearly with the St number in the scope of examination, leading to larger thrust but lower swimming efficiency. Thus, a dimensionless number, St<inf>m</inf>, is introduced to describe the optimal wing motion. This work provides new insights into the propulsion mechanism of aquatic swimmers with flapping-feathering wings and helps design novel bio-inspired aquatic vehicles.
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CHT/CFD analysis of thermal sensitivity of a transonic film-cooled guide vane
(2019-01-01)
Prapamonthon, Prasert
;
Yooyen, Soemsak
;
Sleesongsom, Suwin
Thermal parameters are important variables that have great influence on life time of turbine vanes. Therefore, accurate prediction of the thermal parameters is essential. In this study, a numerical approach for conjugate heat transfer (CHT) and computational fluid dynamics (CFD) is used to investigate thermal sensitivity of a transonic guide vane which is fully film-cooled by 199 film holes. Thermal barrier coating (TBC), i.e., the typical TBC and a new one as the candidate TBC, and turbulence intensity (Tu), i.e., Tu=3.3%, 10% and 20%, are two variables used for the present study. At first the external surface temperatures of the vane material are compared. Next, the TBC surface temperatures are considered. Results show the major role of the lower thermal conductivity of TBC which results in the lower and more uniform temperature on the external surface of the vane substrate. Finally, the thermal sensitivity is presented in terms of the percentage reduction of the external surface temperatures of the vane material and the structural temperatures of the vane material at midspan, including the variations of average and maximum vane temperatures. Results show that TBC and Tu have significant effects on the external surface and structural temperatures of the vane substrate. The lower thermal conductivity of TBC leads to the higher difference between the thermal conductivity of the vane substrate and TBC, the reduction of heat transfer and the more uniform temperature within the vane structure. The results also show more effective protection for the average vane temperature from the two TBCs at higher Tus. However, Tu does not significantly affect the reduction of the maximum vane temperature even though the new TBC, which has the very low thermal conductivity, is used.
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Investigation of cooling performances of a non-film-cooled turbine vane coated with a thermal barrier coating using conjugate heat transfer
(2018-04-01)
Prapamonthon, Prasert
;
Yooyen, Soemsak
;
Sleesongsom, Suwin
;
Dipasquale, Daniele
;
Xu, Huazhao
The aim of this paper is to numerically investigate cooling performances of a non-film-cooled turbine vane coated with a thermal barrier coating (TBC) at two turbulence intensities (Tu = 8.3% and 16.6%). Computational fluid dynamics (CFD) with conjugate heat transfer (CHT) analysis is used to predict the surface heat transfer coefficient, overall and TBC effectiveness, as well as internal and average temperatures under a condition of a NASA report provided by Hylton et al. [NASA CR-168015]. The following interesting phenomena are observed: (1) At each Tu, the TBC slightly dampens the heat transfer coefficient in general, and results in the quantitative increment of overall cooling effectiveness about 16-20%, but about 8% at the trailing edge (TE). (2) The protective ability of the TBC increases with Tu in many regions, that is, the leading edge (LE) and its neighborhoods on the suction side (SS), as well as the region from the LE to the front of the TE on the pressure side (PS), because the TBC causes the lower enhancement of the heat transfer coefficient in general at the higher Tu. (3) Considering the internal and average temperatures of the vane coated with two different TBCs, although the vane with the lower thermal conductivity protects more effectively, its role in the TE region reduces more significantly. (4) For both TBCs, the increment of Tu has a relatively small effect on the reduction of the average temperature of the vane.
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Numerical Investigation on Aerodynamic Drag and Noise of Pantographs with Modified Structures
(2022-01-01)
Yao, Y.
;
Sun, Z.
;
Li, G.
;
Prapamonthon, P.
;
Cheng, G.
It is well known that the pantograph, which works as a complex component of high-speed trains, is an important source of aerodynamic drag and aerodynamic noise of a high-speed train (HST) that can affect HST performance, comfort for passengers, and quietness of nearby communities. Thus, comprehensive studies on aerodynamic characteristics including aerodynamic drag and aerodynamic noise obtained by the pantograph need to be conducted. This work presents the aerodynamic characteristics including aerodynamic resistance and aerodynamic noise generated by the prototype pantograph of a high-speed train running at a speed of 300 km/h using numerical techniques of improved delayed detached-eddy simulation (IDDES) and acoustic finite element method (FEM). Then, the structure of the original pantograph is modified by wrapping the insulators, and the base frame, so that aerodynamic resistance and aerodynamic noise may be reduced as expected. Numerical results obtained from the pantograph without modification, with two modifications to the original design i.e. the base frame, and the insulators, are discussed. Compared to the original pantograph, the two modifications of the pantograph at the base frame and the support insulators are conducive to reducing the aerodynamic drag of the pantograph. However, the results also show that the modified insulator may not achieve considerable success in noise reduction. Only the modified base frame shows that noise is reduced significantly. Therefore, this suggests that the pantograph with base frame modification is a better choice for resistance and noise reduction.

Prapamonthon, Prasert

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