We utilized direct simulation Monte Carlo (DSMC) method to investigate the effectiveness of the NSF equations in the slip and transition regimes. Monatomic argon confined in a micro/nano lid-driven cavity is considered in this study. Full NSF equations accompanied by the first and second order velocity slip and temperature jump boundary conditions are used to investigate non-equilibrium phenomena. It is seen that although velocity profiles are predicted quite accurately by means of proper slip boundary conditions, the NSF equations fail to predict correct shear stress distribution and heat flux direction even in the middle slip regime. It is also seen that applying the second order velocity slip boundary condition in the transition regime reduces the accuracy of the continuum approach. Fourier law, which assumes the heat always fluxes from hotter to colder region, loses its validity in the slip regime and beyond.

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