“…(u 0 , p 0 , θ 0 ), (U 0 , P 0 , Θ 0 ) are solved. Following the standard method on constructing approximate solution by boundary layer expansion (see [27,56,58] and the references therein for example), one can obtain the terms (u i , p i , θ i ) and (U i , P i , Θ i ) order by order. Then we conclude that the approximate solutions (u a , p a , θ a ) for (1.1) can be expressed in the form…”