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 - 10 of 14

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Nucleate boiling enhancement on a pillar structure surface with selected surface vibration modes
(2024-08-01)
Ke, Zhaoqing
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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
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Feng, Qing Song
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Prapamonthon, Prasert
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Cheng, Gong
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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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A web-based semi-empirical numerical tool for accessible liquid swirl injector design
(2025-01-01)
Uhthalye, Thitut
;
Prapamonthon, Prasert
Swirl injectors are vital components to liquid rocket engine combustion intensification, offering high-performance propellant atomisation with relative ease of manufacture. However, despite their widespread use and utility, comprehensive, publicly available practical design methodologies remain scarce in the literature. To address this gap, this paper presents a web-based JavaScript tool employing an iterative semi-empirical numerical method for rapid first-order approximation design of general tangential inlet-type monopropellant and bipropellant liquid swirl injector geometries, based chiefly on the approach described by Bazarov et al. (2004). The tool calculates key geometric and flow parameters—including nozzle radius, radial inlet positions, spray cone angle, and Reynolds numbers—based on user-specified operating conditions such as pressure drop, fluid properties, and geometric coefficients. Special emphasis is given to the efficient implementation of the algorithm for rapid iteration. A computational fluid dynamics validation comparing the computed values against expected flow characteristics is ongoing, with initial results showing promising agreement in limited test cases. Analyses quantifying variances and defining valid regimes of sensible results are in-progress. Additionally, a structured design workflow is also proposed, addressing key limitations such as model prediction deviation due to insufficient air core formation in small injectors. This accessible computation tool aims to assist engineers and students in the predictable and iterative development of swirl injectors.
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EFFECTS OF VANE TRAILING EDGE DETERIORATION ON FLOW PHENOMENA: A CFD SIMULATION OF BROKEN SCENARIOS
(2023-01-01)
Thammachote, Benyapa
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Premyothin, Jitlada
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Tanpradit, Ditthaphat
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Wongsatanawarid, Atikorn
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Dipasquale, Daniele
To achieve high thermal and propulsive efficiencies from an aircraft powerplant using an air-breathing system, the turbine inlet temperature (TIT), a critical design-limit variable, must rise. However, the increment of the TIT is limited by the survivability of the turbine material. Beyond the safety zone of the material, the operation can end in failure. For this reason, the turbine nozzle guide vane (NGV) is a critical component of gas turbine engines because it must operate in hot gas environments. Due to the constraints of effective cooling and the thinnest possible shape of the trailing edge (TE), this region can be suddenly or gradually deteriorated by cracks when the turbine is in long-term operation. This situation can have a seriously negative effect on the engine's performance because the flow field and heat phenomena are different from the usual conditions. Therefore, the problem of vane TE damage is very challenging, and sustainable solutions require a thorough understanding of flow physics and heat transfer mechanisms. A three-dimensional CFD simulation with the SST k-ω turbulence model is used in this work to investigate flow phenomena at the vane trailing edge while subjected to damage effects. The profile of the Mark II vane is used to create vane boundaries in the computational domain. The computational mesh is generated by ICEM and 18 layers are added to the vane surface to capture the flow in the boundary layer. The minimum quality of the mesh is 0.2 and y+ is less than 4.5. The FLUENT software is used as the solver, with second order upwind discretization. Under the compressible flow model, air is used as the burned gas. Broken scenarios in both the streamwise and spanwise directions are presented in a very simplistic manner, with a short, shallow cutback expanding into a long, deep one, namely, 0.1 cm x 1 cm to 0.3 cm x 3 cm. The convergence of the numerical results is considered by the residual of the governing equations. Boundary conditions are set to be the same as experimental data reported by NASA so that numerical results in terms of the pressure distribution along the vane midspan can be validated. The results predicted by the SST k-w turbulence model can provide an acceptable agreement with the experiment. For subsequent simulations, numerical results involving turbulent flow, such as turbulent viscosity, turbulent kinetic energy, vorticity, and streamlines, are compared, and discussed. The findings show that vane TE damage has a significant impact on fluid in motion, particularly the phenomenon of turbulent viscosity. This suggests that heat convection is disrupted.
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Hydrodynamic performance of a penguin wing: Effect of feathering and flapping
(2023-06-01)
Hao, Zhanzhou
;
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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NUMERICAL INVESTIGATION ON DAMAGE SCENARIOS OF VANE TRAILING EDGE USING THERMO-FLUID-STRUCTURAL ANALYSIS
(2025-01-01)
Jeatrakul, Karn
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Tanpradit, Ditthaphat
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Prapamonthon, Prasert
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Raja, Vijayanandh
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Ke, Zhaoqing
Gas-turbine nozzle vanes are used to increase the velocity magnitude of hot gas exiting the combustor. Thus, the vanes must operate at high turbine inlet temperatures (TITs). Essentially, the higher the turbine inlet temperature, the greater the thermal efficiency and propulsive efficiency. Nonetheless, this situation can cause severe damage to the vane material because of the repeated high thermal loads. Using thermo-mechanical analysis, this paper presents damage scenarios of a nozzle vane's trailing edge (TE) and their impact on flow and heat phenomena, including mechanical behavior of the vane material. As the upstream process, computational fluid dynamics (CFD) simulation with conjugate heat transfer (CHT) is used to numerically investigate flow physics and heat transfer phenomena. Then, for the downstream calculations, a static structure model for a steady temperature analysis is used. The NASA-MARK II vane profile is used to define vane boundaries in the computational domain. Broken vane TE scenarios are presented in both the streamwise and spanwise directions, with a short, shallow cutback expanding into a long, deep one from 0.1 cm x 1 cm to 0.3 cm x 3 cm. The numerical results are mainly presented and discussed in terms of variations in surface and internal temperatures, as well as von Mises equivalent stress and strain. The damaged TE, according to the findings, has a significant impact on the thermo-mechanical variations of the vane material. This emphasizes the severity of a damaged vane TE if the turbine is still operating without maintenance.
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Numerical analysis of airside heat and mass transfer characteristics of fin-and-tube heat exchanger under dehumidifying conditions using VOF method
(2026-01-07)
Boonsuk, Krittawit
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Wongsatanawarid, Atikorn
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Ke, Zhaoqing
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Prapamonthon, Prasert
This paper presents a numerical study of the air-side heat and mass transfer characteristics of a single-row plain fin-and-tube heat exchanger with specific geometrical details under dehumidifying conditions using the volume of fluid (VOF) method with species transport. Moist air, a combination of dry air and water vapor, is used as a working fluid. The Lee model, which is embedded in ANSYS Fluent, is used to implement the phase change model. Without additional source terms defined by user-defined functions, the default value is replaced with mass transfer time relaxation for condensation based on the density of the water liquid phase, the water vapor phase, and mass transfer time relaxation for evaporation. The effects of relative humidity and frontal velocity on heat and mass transfer are presented and discussed. The numerical results in terms of heat and mass transfer-based Colburn factors are validated against those found in the open literatures. The findings indicate that the effect of inlet relative humidity to temperature distribution, flow field and distribution pattern of water vapor mass fraction is small. The air-side heat and mass transfer coefficient are higher while the frontal velocity and inlet relative humidity are higher. The inlet relative humidity has little influence on air-side heat and mass performance when the frontal velocity is low.
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Numerical Study on Flow Physics of Damaged Vane Trailing Edge
(2024-01-01)
Thammachote, B.
;
Premyothin, J.
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Khumhaeng, S.
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Tanpradit, D.
;
Dipasquale, D.
According to practical applications in gas turbines, the turbine's nozzle guide vane (NGV) is the first downstream component of the combustor that experiences high thermal loads from burned gases. This situation can severely damage the vane material, particularly the trailing edge (TE). This is because of the limitation of TE thickness and the difficulty of effective cooling in that region. Moreover, the deterioration of the TE surface leads to vane fatalities and has a negative impact on turbine performance because the flow field is unfavorably changed during the operation. This paper aims to numerically study the flow physics of a damaged vane TE using a 3D steady-flow CFD simulation with the SST k-turbulence model. Under the assumptions of ideal gas and compressible flow, air is used as the burned gas. To simplify the vane damage shape, the broken pattern at the TE is given in a long cutback geometry in the simulation. Numerical results in terms of turbulent kinetic energy (TKE), vorticity magnitude, turbulent viscosity, and streamlines are compared and discussed. The interesting findings show that with the inclusion of the damaged TE, the TKE and turbulent viscosity in the broken region increase dramatically on both the midspan and vertical planes. Furthermore, an increment in the vortex size is observed on the midspan plane. However, the vortex centers along the broken region disappear and are replaced by smooth streamlines.
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Numerical investigation of effects of damaged and repaired surfaces on flow behavior of nozzle vane trailing edge
(2024-01-01)
KHUMHAENG, Siwanart
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SUKSA, Thitapa
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LAOHALERTCHAI, Nutcha
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CHAIPRASIT, Benyapa
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PRAPAMONTHON, Prasert
The nozzle guide vane, which is a stationary part of a gas turbine, is a critical component of gas turbine engines because it must operate under harsh conditions with high pressure and temperature. Unfortunately, when a gas turbine runs for a long time, the turbine vane is subjected to repeated thermal load. This increases the possibility of fatigue damage and crack failure, thereby reducing the vane material's lifespan. In practice, the risk of failure at the trailing edge (TE) of a turbine vane is very high due to the reasons of shape configuration and cooling performance. The TE damage disturbs the flow physics of compressible air passing the vane TE, resulting in flow phenomena and heat convection. The study aims to numerically investigate the effects of damaged surfaces at the TE of a turbine vane on its flow behavior using computational fluid dynamics (CFD) with the SST k-w turbulence model. To simplify the simulation, the effects of the TE failure are presented by using two basic patterns, i.e., long (continuous) cutback damage, and two-short (discrete) cutback damage. To complete the investigation, a further study on the effects of repaired surfaces is included as well. The numerical results show the effects of damaged and repaired surfaces on flow behavior, particularly the vortex formation and the level of turbulent kinetic energy (TKE) in the TE region. Specifically, the damaged vane surface significantly increases the TKE level in the TE region, particularly the two-short damaged surface, which TKE shoots up to 7000-8000 m2/s2. Meanwhile, TKE in the normal and long damaged case is around 1500 and 4000 m2/s2. With the restoration of the vane surfaces, it can reduce the TKE level in the TE region. For instance, TKE is uniformly around 1750 m2/s2 for the long repaired surface.
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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
;
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.

Prapamonthon, Prasert

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