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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.
3
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Comparative CFD modeling of foam and conventional pellet catalysts in glycerol steam reforming
(2025-07-15)
Simasatitkul, Lida
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Phitchayakorn, Chattharika
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Amornraksa, Suksun
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Anantpinijwatna, Amata
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Assabumrungrat, Suttichai
A novel approach to glycerol valorization via steam reforming was investigated through computational fluid dynamics (CFD) modelling. The performance characteristics of conventional pellet catalysts were compared with foam catalysts in a 6-inch diameter packed bed reactor. A two-dimensional pseudo-homogeneous steady-state model was employed to evaluate catalyst configurations ranging from 10 to 30 pores per inch (PPI). The foam catalyst structures exhibited superior performance across key metrics, achieving maximum hydrogen yield (60 %) at one-third of the reactor length whilst reducing pressure drop by 95 % compared to conventional pellets. Within the foam configurations, the 10PPI variant demonstrated optimal performance characteristics, with an 80 % reduction in normalized pressure drop compared to 30PPI, whilst maintaining comparable product yields. The enhanced performance was attributed to the open-cell architecture, which facilitated improved mass transfer and reduced diffusion limitations. These findings suggest that foam catalysts represent a promising alternative to conventional pellet configurations for glycerol steam reforming processes.
2
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A web-based semi-empirical numerical tool for accessible liquid swirl injector design
(2025-01-01)
Uhthalye, Thitut
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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.
9
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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.
1
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A suitable shape of the suction head for a cleaning process in a factory developed by computational fluid dynamics
(2021-11-01)
Thongsri, Jatuporn
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Tangsopa, Worapol
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Khongsin, Jirawat
The previous shape of the suction head (SH) employed in a cleaning process in a factory had a low performance, removed fewer particles, and generated an annoying noise. Therefore, new shapes of SH have been proposed to solve the issues and the cleaning performance was investigated by the Shear Stress Transport (SST) k-ω turbulence, Discrete Phase (DP), Large Eddy Simulation (LES), and Ffowcs Williams and Hawkings (FW–H) models in a transient state of computational fluid dynamics (CFD). The SST k-ω and DP models were applied to determine the airflow, suspension velocity, cleaning region, and particle trace. In addition, the LES and FW–H models were used to evaluate the noise, sound pressure level, and frequency generated from the proposed shapes. All simulation results were validated with the air velocity and noise measurements and were analyzed to find a suitable shape. The simulation and experimental results revealed that the shapes of the SH affected the cleaning performance and noise generation. The higher the air velocity, the higher the noise generation. The suitable shape delivered a 4.37% better particle removing performance and 11.1 dB less noise generation than the previous shape. The outcomes of this research are the suitable shape of the SH and the research methodology which enabled the application of both CFD and experiments to solve the issue to help enhance the efficiency of the cleaning process in an actual factory.
1
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Numerical investigation of the effect of constant velocity and constant residence time scaling criteria on the natural gas mild combustion
(2019-01-01)
Suksam, Niwat
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Charoensuk, Jarruwat
This paper concerns with effect of scaling on performance of MILD combustor when increasing its geometry and thermal throughput from the 0.58 MW prototype to its scaled-up versions of 5.8 MW. The constant velocity (CV) and constant residence time (CRT) scaling approaches were used in this work. Their performances were simulated with a numerical model for MILD combustion which was thoroughly validated against existing experimental data. It was found that despite MILD condition could be successfully maintained with both scaling approaches up to the scaling factor of 10, the effect of CV scaling could lead to elevated NO<inf>x</inf> emission due to increase in flow retention time in hot environment. The results were also discussed in term of Damköhler number. Despite of promising technology of MILD combustion for low-NO<inf>x</inf> emission, care must be taken on NO<inf>x</inf> emission level when scaling up with large scale factor under the CV criteria. As for the CRT criteria with increasing inlet velocity with the scale factor, the fuel and air supply pressure should be considered as a constrain when scaling up with large scale factor.

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