In the present study, we investigate gas flow in a micro-/nanochannel by using the two relaxation time lattice Boltzmann equation (TRT-LBE). The wall function approach is employed in order to consider the effect of Knudsen layer in transition flow regime. In this context, two different wall functions called power law and exponential functions are applied to pressure-driven gas flow through a micro-/nanochannel. Also, the slip velocity is realized by defining a relation between the relaxation times of the model. The advantage of the present approach over previous slip boundary conditions is ease of implementation. The TRT-LBE used in this study is comparable with the single relaxation time (SRT) model in simplicity and computational cost, but the additional relaxation time enables the model to treat the slip velocity more accurately. In the results section, we evaluate our model against direct simulation Monte Carlo (DSMC), information preservation (IP) and linearized Boltzmann solution. The accuracy of power law and exponential functions in prediction of velocity profiles, pressure distribution and mass flow rate is also investigated. The results show that the TRT-LBE using wall function correction can satisfactorily predict the flow behavior up to the upper end of the transition flow regime.

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