Body-force modelling in thermal compressible flows with lattice Boltzmann method

Body force modelling in lattice Boltzmann method (LBM) has been extensively studied in the incompressible limit but rarely discussed for thermal compressible flows. Here we present a systematic approach of incorporating body force in LBM which is valid for thermal compressible and non-equilibrium flows. In particular, a LBM forcing scheme accurate for the energy equation with second-order time accuracy is given. New and essential in this scheme is the third-moment contribution of the force term. It is shown via Chapman-Enskog analysis that the absence of this contribution causes an erroneous heat flux quadratic in Mach number and linear in temperature variation. The theoretical findings are verified and the necessity of the third-moment contribution demonstrated by numerical simulations.