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Jafar Ghazanfarian

Dourna Jamshideasli, Abbas Abbassi, Jafar Ghazanfarian
Thermal Lattice Boltzmann Method for Curved Boundaries in the Transition Regime

In this paper, the three-dimensional (3D) Thermal lattice Boltzmann (TLBM) BGK model is developed to simulate the pressure-driven rarefied gaseous flow within the long circular channel with constant temperature wall in the transition regime (0.1 <Kn<1) by employing the most common model (D3Q15). The captured nonlinear behavior of gas in Knudsen layer (KL) which dominates the flow characteristics in small scale gas flows and is as thick as a few molecular mean free path (MFP) from the wall, by modifying the near-wall correction function of the MFP along with the variation of properties with density and temperature distributions are implemented in a new formulation for the relaxation time. In addition, an appropriate combination of advanced high accuracy straight boundary conditions and a 3D extension of available curved boundary conditions by identifying the nodes either adjacent to solid nodes or flow nods on the computational domain with the structured mesh in Cartesian coordinate are employed in the present research. The results are reported in the term of small-scale phenomenon such as slip-velocity and temperature jump which are manifestations of the cases with non-zero Kn number. Due to the deficiency of the continuum presumption in Navier–Stokes solvers for high Knudsen flows, the present study suggests that TLBM is a high-efficient tool applicable to the theoretical development of low speed gas flow study with high Knudsen number which typically falls within the realm of MEMS/NEMS by virtue of its more straightforward boundary treatments and higher computation capability compared to the DSMC or other numerical approaches.



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