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Author: search.filters.author.Prapamonthon, PrasertSubject: search.filters.subject.heat transfer

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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
    ;
    Prapamonthon, Prasert
    ;
    Tanpradit, Ditthaphat
    ;
    Wongsatanawarid, Atikorn
    ;
    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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    NUMERICAL ANALYSIS OF FILM COOLING FLOW OVER FLAT PLATE WITH CONVECTIVE HEAT TRANSFER CONDITIONS
    (2025-01-01)
    Jeatrakul, Karn
    ;
    Koysomboon, Annop
    ;
    Prapamonthon, Prasert
    ;
    Rattanakijsuntorn, Komsan
    Film cooling is a systematically designed and widely used technique in cutting-edge gas turbine engines to reduce the surface temperature of gas turbine blades and endwalls, thereby lowering material temperature. Cooling air is emitted from the film holes to protect the external surface, which is exposed to high temperatures from the mainstream gas. As a result, the flow physics of cooling air mixing with the mainstream is critical, and it remains difficult for gas turbine designers to improve cooling efficacy due to the complexity of heat convection phenomena. This paper presents a numerical study onto problems of convective heat transfer in film cooling flow over a flat plate model using 3D computational fluid dynamics (CFD) available in STAR CCM+. The SST k- turbulence model and the realizable k- turbulence model with two-layer all y+ wall treatment are taken into consideration. To solve the problems, the flat plate surface is subjected to adiabatic (Cases 1-2) and constant heat flux conditions of 500 and 1000 W/m<sup>2</sup> (Cases 3-6, respectively). The study is conducted at the density ratio (DR) of 1.2 and blowing ratios (BRs) of 0.3 and 0.6. Numerical solutions for both conditions are presented in terms of adiabatic film effectiveness (ηad), dimensionless temperature (θ), and Nusselt number (Nu). Based on a comparative analysis of adiabatic and heat flux conditions, the results show that both the centerline and laterally adiabatic film effectiveness at the two BRs decrease streamwise. At the same BR, the dimensionless temperature values are lower at 1000 W/m<sup>2</sup> than at 500 W/m<sup>2</sup>. This includes less film coverage in the downstream. At BR = 0.6, increasing heat flux from 500 W/m<sup>2</sup> to 1000 W/m<sup>2</sup> significantly reduces film coverage size in both streamwise and spanwise directions.
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    NUMERICAL INVESTIGATION ON DAMAGE SCENARIOS OF VANE TRAILING EDGE USING THERMO-FLUID-STRUCTURAL ANALYSIS
    (2025-01-01)
    Jeatrakul, Karn
    ;
    Tanpradit, Ditthaphat
    ;
    Prapamonthon, Prasert
    ;
    Raja, Vijayanandh
    ;
    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.