The flow over periodically arranged hills in a rectangular channel is studied experimentally by highly resolved particle image velocimetry. We focus here on the formation and structure of the wall layer on the rising flank of the hill. We found that the Reynolds shear stresses in the vicinity of the wall are considerably lower than one would expect for a turbulent wall-bounded flow, suggesting that turbulent boundary layer dynamics could not develop and a laminar dynamics was prevalent. We therefore evaluate the possibility of approximating the velocity distribution in the near-wall region using the Falkner-Skan solution for laminar boundary layers with pressure gradient. Such an approximation could contribute to the development of wall models for numerical simulations.     «

The flow over periodically arranged hills in a rectangular channel is studied experimentally by highly resolved particle image velocimetry. We focus here on the formation and structure of the wall layer on the rising flank of the hill. We found that the Reynolds shear stresses in the vicinity of the wall are considerably lower than one would expect for a turbulent wall-bounded flow, suggesting that turbulent boundary layer dynamics could not develop and a laminar dynamics was prevalent. We there...     »