Prapamonthon, Prasert

Preferred name

Alternative Name

PRAPAMONTHON, Prasert

Prapamonthon, P.

Main Affiliation

International Academy of Aviation Industry

prasert.pr@kmitl.ac.th

Now showing 1 - 8 of 8

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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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Aerodynamic optimization using passive control devices near the bogie cabin of high-speed trains
(2022-09-01)
Yao, Yongfang
;
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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Numerical investigation of the aerodynamic noise mechanism in high-speed trains operating at 400 km/h
(2025-08-01)
Huang, Junhui
;
Lu, Weishuang
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Sun, Zhenxu
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Prapamonthon, Prasert
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Guo, Dilong
In this study, an improved delayed detached eddy simulation in conjunction with the Ffowcs Williams-Hawkings acoustic analogy is used to numerically compare the aerodynamic noise characteristics of the CR400BF and CR450 high-speed trains operating at 350 and 400 km/h, respectively. The results show that although there are noticeable changes in the distribution of acoustic energy, increasing the operating speed to 400 km/h has no discernible effect on the locations of the main noise sources. The airflow characteristics are optimized by using streamlined front designs, bogie web plates, and fully enclosed skirts, resulting in reduced turbulent kinetic energy and pressure fluctuations. As a result, the noise amplitude in the front car region is effectively reduced, while the formation of small-scale vortices, which can cause noise at high frequencies, is inhibited. However, because of the smoothing of the underbody and the lack of bogie web plates in the middle sections, higher airflow velocities are introduced, intensifying the interaction with the third and fourth bogies. This leads to the increase in noise amplitudes in these regions.
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Multi-objective design optimization of the combinational configuration of the upstream energy deposition and opposing jet for drag reduction in supersonic flows
(2020-10-01)
Ju, Shengjun
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Sun, Zhenxu
;
Yang, Guowei
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Prapamonthon, Prasert
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Zhang, Junyuan
Optimization design has been widely used in the supersonic vehicle design process and the drag reduction characteristic is an important objective of the optimization. The drag reduction mechanism applied to the blunt body with the combinational configuration of the upstream energy deposition and opposing jet for drag reduction has been conducted numerically. In the current study, the three-dimensional coupled implicit compressible Reynolds Averaged Navier-Stokes equations and Menter's shear stress transport turbulence model are employed to simulate the flow fields around the blunt body with the combined method. The results show that in the jet-to-freestream total-pressure ratio of 0.2 and 0.4, the drag is reduced by 47.44% and 45.96%, respectively. Further, the Latin hypercube method is used for the generation of initial samples for optimization and the multi-objective design optimization algorithm coupled with the Kriging model surrogate model is applied to determine optimal flow control parameters. The drag reduction factor R<inf>d</inf> and drag reduction effectiveness E<inf>eff</inf> are selected as optimization objectives. The Pareto-optimal front for the multi-objective design optimization results is acquired and there exists a challenging tradeoff between the two optimization objectives. The drag reduction factor R<inf>d</inf> and drag reduction effectiveness E<inf>eff</inf> further increase as much as 28.16% and 116.47%, respectively. The jet has a stronger penetration in the optimum design condition, and the findings suggest that the strategy of adding energy spot to the upstream flow field of the opposing jet can be an effective way for drag reduction.
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Numerical Solutions of Transonic to Supersonic Flow over Backward-Forward Facing Step with Heat Flux Conditions
(2026-03-06)
Jeatrakul, Karn
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Prapamonthon, Prasert
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Tanpradit, Ditthaphat
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Wongsatanawarid, Atikorn
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Hao, Zhanzhou
Flows phenomena over a backward-facing step (BFS) and a forward-facing step (FFS) are critical for understanding flow physics in engine, aerodynamic, heat transfer systems. Given the rapid advancement of high-speed technology, the presence of shock waves and aerodynamic heat can have an impact on flow physics, thereby emphasizing the importance of high-speed flow over BFS and FFS with heat transfer. This paper presents numerical solutions of steady two-dimensional viscous turbulent flow over a continuous backward-forward facing step (BFFS) in the transonic to supersonic regime with heat flux conditions using STAR-CCM+. The compressible air and k-ϵ turbulence model are used for the simulations. The effects of inlet Mach numbers ranging from 0.8 to 3.0 and bottom step heat fluxes varying from 0.5 to 10.0 kW/m<sup>2</sup> on flow physics are investigated. Numerical results depict flow phenomena such as flow separation, recirculation, and shock wave, as well as thermal distribution. Furthermore, the results show that variations in the inlet Mach number affect flow behaviors, while higher heat fluxes cause dramatical changes in Nusselt number, especially, in the BFS corner for transonic flow.
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Parametric study on drag reduction with the combination of the upstream energy deposition and the opposing jet configuration in supersonic flows
(2020-06-01)
Ju, Shengjun
;
Sun, Zhenxu
;
Yang, Guowei
;
Prapamonthon, Prasert
;
Zhang, Junyuan
The drag reduction characteristics play an important role in the supersonic vehicle design phase. According to two drag reduction schemes, the opposing jet and the upstream energy deposition have aroused the widespread interest of researchers. In the current study, the drag reduction effectiveness of a blunt body with the combination of the upstream energy deposition and the opposing jet configuration in supersonic flows is investigated numerically. The three-dimensional coupled implicit compressible Reynolds Averaged Navier-Stokes (RANS) equations coupled with the Menter's shear stress transport (SST) turbulence model are applied to numerically predict flow fields of the blunt body, the variance analysis method is introduced to a parametric study on the drag reduction. Results indicate that a larger overall drag is decreased by the combinational configuration than the single strategies of the opposing jet and the energy deposition. The proposal of the combination of the upstream energy deposition and the opposing jet configuration can be used as an effective method of drag reduction. Meanwhile, due to the existence of the upstream energy deposition, the stability and penetrability of the opposing jet substantially increase, especially for the long penetration mode. Further, some recommendations are provided for the drag reduction factor and drag reduction effectiveness.
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Numerical Solutions of Heat Convection Problems in Film Cooling Flow Over Adiabatic and Diabatic Flat Plates
(2026-03-06)
Jeatrakul, Karn
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Prapamonthon, Prasert
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Wongsatanawarid, Atikorn
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Wang, Yeteng
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Hao, Zhanzhou
This paper presents numerical solutions for film cooling flow over a flat plate subjected to heat convection problems, namely (1) adiabatic, and (2) diabatic plates with constant heat fluxes of 500 and 1000 W/m<sup>2</sup>. The governing equations and realizable k-ε turbulence model are solved to provide numerical solutions in terms of film effectiveness for the adiabatic case, and dimensionless temperature and Nusselt number for the diabatic case. Numerical solutions are carried out at two film hole angles i.e. α = 25° and 35° and two blowing ratios i.e. BR = 0.3 and 0.6. The numerical solutions indicate that the smaller angle and lower blowing ratio can provide better effective cooling on the flat plate for both problem conditions. In addition, the strong influence of the blowing ratio on the film cooling flow is observed. When the heat flux is included, the Nusselt number increases in spanwise and streamwise direction with the heat flux.
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INFLUENCE of COOLANT on COOLING PERFORMANCE SENSITIVITY of INTERNALLY CONVECTIVE TURBINE VANE
(2021-01-01)
Chotroongruang, Thanapat
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Prapamonthon, Prasert
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Thongdee, Rungsimun
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Thongmuenwaiyathon, Thanapat
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Sun, Zhenxu
Based on the Brayton cycle for gas-turbine engines, the high thermal efficiency and power output of a gas-turbine engine can be obtainable when the gas-turbine engine operates at high turbine inlet temperatures. However, turbine components e.g., inlet guide vane, rotor blade, and stator vane request high cooling performance. Typically, internal cooling and film cooling are two effective techniques that are widely used to protect high thermal loads for the turbine components in a stateof- the-art gas turbine. Consequently, the high thermal efficiency and power output can be obtained, and the turbine lifespan can be prolonged, also. On top of that, a comprehensive understanding of flow and heat transfer phenomena in the turbine components is very important. As a result, both experiments and simulations have been used to improve the cooling performance of the turbine components. In fact, the cooling air used in the internal cooling and film cooling is partially extracted from the compressor. Therefore, variations in the cooling air affect the cooling performance of the turbine components directly. This paper presents a numerical study on the influence of the cooling air on cooling-performance sensitivity of an internally convective turbine vane, MARK II using the computational fluid dynamics (CFD)/conjugate heat transfer (CHT) with the SST k- turbulence model. Result comparisons are conducted in terms of pressure, temperature, and cooling effectiveness under the effects of the inlet temperature, mass flow rate, turbulence intensity, and flow direction of the cooling air. The cooling-performance sensitivity to the coolant parameters is shown through variations of local cooling effectiveness, and area and volume-weighted average cooling effectiveness.

Prapamonthon, Prasert

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