A 13-speed lattice Bhatnagar-Gross-Krook model on hexagonal lattice is used
to investigate thermohydrodynamics. An adjustable parameter k is introduce
d in the process to determine the parameter in local equilibrium distributi
on function according to Fourier law. As a result, the thermal conductivity
is lambda = (2 rho epsilon + 9k)(tau - 0.5), so that the Prandtl number be
comes tunable and Remolds number can be raised effectively.