  The rarefied effect of gas flow in microchannel is significant and cannot be
well described by traditional hydrodynamic models. It has been know that
discrete Boltzmann model (DBM) has the potential to investigate flows in a
relatively wider range of Knudsen number because of its intrinsic kinetic
nature inherited from Boltzmann equation. It is crucial to have a proper
kinetic boundary condition for DBM to capture the velocity slip and the flow
characteristics in the Knudsen layer. In this paper, we present a DBM combined
with Maxwell-type boundary condition model for slip flow. The tangential
momentum accommodation coefficient is introduced to implement a gas-surface
interaction model. Both the velocity slip and the Knudsen layer under various
Knudsen numbers and accommodation coefficients can be well described. Two kinds
of slip flows, including Couette flow and Poiseuille flow, are simulated to
verify the model. To dynamically compare results from different models, the
relation between the definition of Knudsen number in hard sphere model and that
in BGK model is clarified.
