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Author: search.filters.author.Hao, Zhanzhou

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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 Solutions of Heat Convection Problems in Film Cooling Flow Over Adiabatic and Diabatic Flat Plates
    (2026-03-06)
    Jeatrakul, Karn
    ;
    Prapamonthon, Prasert
    ;
    Wongsatanawarid, Atikorn
    ;
    Wang, Yeteng
    ;
    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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    Hydrodynamic performance of a penguin wing: Effect of feathering and flapping
    (2023-06-01)
    Hao, Zhanzhou
    ;
    Yin, Bo
    ;
    Prapamonthon, Prasert
    ;
    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.