Browsing by Author "Xiong, Xin"

Now showing 1 - 3 of 3
  • Thumbnail Image
    ItemOpen Access
    Critical assessment of the lattice Boltzmann method for cavitation modelling based on single bubble dynamics
    (Springer, 2024-05-01) Xiong, Xin; Teschner, Tom-Robin; Moulitsas, Irene; Józsa, Tamás István
    The lattice Boltzmann Method (LBM) is recognised as a popular technique for simulating cavitation bubble dynamics due to its simplicity. In the validation of LBM results, the Rayleigh-Plesset (R-P) equation is commonly employed. However, most studies to date have neglected the impact of simulation settings on the predictions. This article sets out to quantify the impact of LBM domain size and bubble size, and the initial conditions of the R-P equations on the predicted bubble dynamics. First, LBM results were validated against the classical benchmarks of Laplace’s law and Maxwell’s area construction. LBM results corresponding to these fundamental test cases were found to be in satisfactory agreement with theory and previous simulations. Secondly, a one-to-one comparison was considered between the predictions of the LBM and the R-P equation. The parameters of the two models were matched based on careful considerations. Findings revealed that a good overlap between the predictions is observable only under certain conditions. The warming-up period of the LBM simulations, small domain size, and small bubble radius were identified as key factors responsible for the measured differences. The authors hope that the results will promote good simulation practices for cavitation simulation including both single bubbles and bubble clusters.
  • Thumbnail Image
    ItemOpen Access
    Modeling rapid solidification and melting processes for multiphase flows in a welding technology application
    (Miskolc University Press, 2022-08-16) Xiong, Xin; Könözsy, László Z.
    This article presents unsteady simulations of laser welding based on a rapid solidification/melting model using the ANSYS-FLUENT software package with the implementation of a UDF (User Defined Function) C code. It assumes a flat interface of liquid and gas without plasma plume, evaporation and reflection and absorption effect. In the simulations, a variety of parameters are considered with different welding speeds and laser powers. The results show that with the increase of laser power, liquid fraction and velocity, penetration depth and bead width all increase. In contrary, with the increase of welding speed, the temperature, liquid fraction, penetration depth, and bead width all decrease, while the velocity magnitude is an exception. It has also been found that the increase of welding speed distorts the pool shape and forms a long tail in temperature, liquid fraction and velocity contour. The buoyancy force did not have a significant impact on the results, while the convective term makes the velocity, temperature and liquid fraction smaller. Furthermore, the negative Marangoni shear stress makes the velocity along the height and the width direction smaller in the middle of the workpiece and larger on the edges. The simulation results show a similar tendency to that obtained by other authors. The reason for the possible differences is due to the unsteadiness of the fluid flow field and the slightly different boundary conditions imposed in the model presented here. The novelties of this work are unsteady simulations, new boundary conditions and parametric studies relevant to industrial applications.
  • Thumbnail Image
    ItemOpen Access
    Simulate cavitation bubble with single component multi-phase Lattice Boltzmann method
    (2023-04-21) Xiong, Xin; Teschner, Tom-Robin; Moulitsas, Irene
    Cavitation occurs when the pressure drops below a critical value at which point it can cause great damage to the machines such as propellers. In this study, a two-dimensional single bubble with different pressure differences between the boundary and the bubble will be studied based on the single component Shan-Chen model with the Carnahan-Starling (C-S) Equation of State (EOS) incorporated, which is similar to the model in [1-2]. Firstly, the model with the C-S EOS will be validated based on Maxwell’s equal area construction. The equilibrium density of liquid and vapor is obtained using a flat interface simulation according to [3]. It was demonstrated that the model has great thermal consistency according to this validation. Furthermore, we show results for a single bubble case for which its growth and collapse can be validated against the RayleighPlesset (R-P) equation with various pressure differences. Results show good agreement with the R-P equation and literature.