convection flow over a backward-facing step. Direct numerical simulations are performed in
a two-dimensional horizontal channel of expansion ratio ER= 2 at step level. The effects of
the temperature difference between the heated bottom wall and the inflow temperature are
investigated by keeping constant the Richardson number at 1. The covered range of Grashof
and Reynolds numbers is respectively 3.31× 104⩽ Gr⩽ 2.72× 105 and 182.03⩽ Re⩽ …