The characteristics of turbulent boundary layers over hilly terrain depend strongly on the
slope and surroundings, especially the upstream roughness conditions. In this study, Large-
eddy simulation (LES) is systematically performed to study the turbulent boundary layer over
two-dimensional hills. Two kinds of hill shape, a steep one with stable separation and a low
one without stable separation, and two kinds of upstream roughness condition
corresponding to two kinds of velocity profile are considered. A wind tunnel experiment is …