A compressible lattice-Boltzmann model coupled with non-equilibrium extrapolation method are adopted to simulate gas flow in microchannels at slip regime (Kn≤0.1).Numerical results,including velocity profiles at outlet,pressure distributions and mass flowrates,agree well with analytical solutions and experimental results.In addition,gas flow in a 180 degree curved channel is numerically simulated.It shows that boundary layer separation is suppressed by slip velocity at the wall.In addition,mass flowrate of a curved channel is smaller than that of a straight one.

An LB-DF/FD method,combined with lattice Boltzmann method (LBM) and direct-forcing/fictitious domain (DF/FD) scheme,is set up for fluid-solid interaction problems.The LB-DF/FD method uses two unrelated meshes to avoid re-meshing procedure.They are Eulerian mesh for the flow domain and Lagrangian mesh for the solid domain.LB-DF/FD method overcomes fluctuations in computation of forces on solid particle in conventional LBM.The method is validated with simulation of flow past a fixed circular cylinder,a circular cylinder moving in an infinite channel or rotating in an infinite field.Flow around two circular cylinders in tandem at low Reynolds numbers is simulated by using LB-DF/FD method.Effects of spacing gap between cylinders (g^*) and Renolds number (Re) are investigated.Numerical results including streamlines,lift and drag force and torque exerted on the cylinder,at Re=0.001,0.1 and 10,0.2≤g^*≤8.0 are presented.g^* shows remarkable effect on lift and drag force and torque exerted on cylinders.Stokes cell number and drag force exerted on cylinders depend on Re.